diff --git a/cache/stores/mongodb/MongoDB/LICENSE b/cache/stores/mongodb/LICENSE
similarity index 100%
rename from cache/stores/mongodb/MongoDB/LICENSE
rename to cache/stores/mongodb/LICENSE
diff --git a/cache/stores/mongodb/MongoDB/BulkWriteResult.php b/cache/stores/mongodb/MongoDB/BulkWriteResult.php
index cdf6654ea89..68af2cd751e 100644
--- a/cache/stores/mongodb/MongoDB/BulkWriteResult.php
+++ b/cache/stores/mongodb/MongoDB/BulkWriteResult.php
@@ -25,13 +25,16 @@ use MongoDB\Exception\BadMethodCallException;
  */
 class BulkWriteResult
 {
+    /** @var WriteResult */
     private $writeResult;
+
+    /** @var mixed[] */
     private $insertedIds;
+
+    /** @var boolean */
     private $isAcknowledged;
 
     /**
-     * Constructor.
-     *
      * @param WriteResult $writeResult
      * @param mixed[]     $insertedIds
      */
diff --git a/cache/stores/mongodb/MongoDB/ChangeStream.php b/cache/stores/mongodb/MongoDB/ChangeStream.php
index 98a703fadd7..3c360fa8633 100644
--- a/cache/stores/mongodb/MongoDB/ChangeStream.php
+++ b/cache/stores/mongodb/MongoDB/ChangeStream.php
@@ -17,15 +17,15 @@
 
 namespace MongoDB;
 
-use MongoDB\BSON\Serializable;
-use MongoDB\Driver\Cursor;
+use Iterator;
+use MongoDB\Driver\CursorId;
 use MongoDB\Driver\Exception\ConnectionException;
 use MongoDB\Driver\Exception\RuntimeException;
 use MongoDB\Driver\Exception\ServerException;
-use MongoDB\Exception\InvalidArgumentException;
 use MongoDB\Exception\ResumeTokenException;
-use IteratorIterator;
-use Iterator;
+use MongoDB\Model\ChangeStreamIterator;
+use function call_user_func;
+use function in_array;
 
 /**
  * Iterator for a change stream.
@@ -42,27 +42,39 @@ class ChangeStream implements Iterator
      */
     const CURSOR_NOT_FOUND = 43;
 
-    private static $errorCodeCappedPositionLost = 136;
-    private static $errorCodeInterrupted = 11601;
-    private static $errorCodeCursorKilled = 237;
+    /** @var array */
+    private static $nonResumableErrorCodes = [
+        136, // CappedPositionLost
+        237, // CursorKilled
+        11601, // Interrupted
+    ];
 
-    private $resumeToken;
+    /** @var callable */
     private $resumeCallable;
-    private $csIt;
+
+    /** @var ChangeStreamIterator */
+    private $iterator;
+
+    /** @var integer */
     private $key = 0;
+
+    /**
+     * Whether the change stream has advanced to its first result. This is used
+     * to determine whether $key should be incremented after an iteration event.
+     *
+     * @var boolean
+     */
     private $hasAdvanced = false;
 
     /**
-     * Constructor.
-     *
      * @internal
-     * @param Cursor $cursor
-     * @param callable $resumeCallable
+     * @param ChangeStreamIterator $iterator
+     * @param callable             $resumeCallable
      */
-    public function __construct(Cursor $cursor, callable $resumeCallable)
+    public function __construct(ChangeStreamIterator $iterator, callable $resumeCallable)
     {
+        $this->iterator = $iterator;
         $this->resumeCallable = $resumeCallable;
-        $this->csIt = new IteratorIterator($cursor);
     }
 
     /**
@@ -71,15 +83,29 @@ class ChangeStream implements Iterator
      */
     public function current()
     {
-        return $this->csIt->current();
+        return $this->iterator->current();
     }
 
     /**
-     * @return \MongoDB\Driver\CursorId
+     * @return CursorId
      */
     public function getCursorId()
     {
-        return $this->csIt->getInnerIterator()->getId();
+        return $this->iterator->getInnerIterator()->getId();
+    }
+
+    /**
+     * Returns the resume token for the iterator's current position.
+     *
+     * Null may be returned if no change documents have been iterated and the
+     * server did not include a postBatchResumeToken in its aggregate or getMore
+     * command response.
+     *
+     * @return array|object|null
+     */
+    public function getResumeToken()
+    {
+        return $this->iterator->getResumeToken();
     }
 
     /**
@@ -91,60 +117,40 @@ class ChangeStream implements Iterator
         if ($this->valid()) {
             return $this->key;
         }
+
         return null;
     }
 
     /**
      * @see http://php.net/iterator.next
      * @return void
+     * @throws ResumeTokenException
      */
     public function next()
     {
         try {
-            $this->csIt->next();
-            if ($this->valid()) {
-                if ($this->hasAdvanced) {
-                    $this->key++;
-                }
-                $this->hasAdvanced = true;
-                $this->resumeToken = $this->extractResumeToken($this->csIt->current());
-            }
-            /* If the cursorId is 0, the server has invalidated the cursor so we
-             * will never perform another getMore. This means that we cannot
-             * resume and we can therefore unset the resumeCallable, which will
-             * free any reference to Watch. This will also free the only
-             * reference to an implicit session, since any such reference
-             * belongs to Watch. */
-            if ((string) $this->getCursorId() === '0') {
-                $this->resumeCallable = null;
-            }
+            $this->iterator->next();
+            $this->onIteration($this->hasAdvanced);
         } catch (RuntimeException $e) {
-            if ($this->isResumableError($e)) {
-                $this->resume();
-            }
+            $this->resumeOrThrow($e);
         }
     }
 
     /**
      * @see http://php.net/iterator.rewind
      * @return void
+     * @throws ResumeTokenException
      */
     public function rewind()
     {
         try {
-            $this->csIt->rewind();
-            if ($this->valid()) {
-                $this->hasAdvanced = true;
-                $this->resumeToken = $this->extractResumeToken($this->csIt->current());
-            }
-            // As with next(), free the callable once we know it will never be used.
-            if ((string) $this->getCursorId() === '0') {
-                $this->resumeCallable = null;
-            }
+            $this->iterator->rewind();
+            /* Unlike next() and resume(), the decision to increment the key
+             * does not depend on whether the change stream has advanced. This
+             * ensures that multiple calls to rewind() do not alter state. */
+            $this->onIteration(false);
         } catch (RuntimeException $e) {
-            if ($this->isResumableError($e)) {
-                $this->resume();
-            }
+            $this->resumeOrThrow($e);
         }
     }
 
@@ -154,40 +160,7 @@ class ChangeStream implements Iterator
      */
     public function valid()
     {
-        return $this->csIt->valid();
-    }
-
-    /**
-     * Extracts the resume token (i.e. "_id" field) from the change document.
-     *
-     * @param array|document $document Change document
-     * @return mixed
-     * @throws InvalidArgumentException
-     * @throws ResumeTokenException if the resume token is not found or invalid
-     */
-    private function extractResumeToken($document)
-    {
-        if ( ! is_array($document) && ! is_object($document)) {
-            throw InvalidArgumentException::invalidType('$document', $document, 'array or object');
-        }
-
-        if ($document instanceof Serializable) {
-            return $this->extractResumeToken($document->bsonSerialize());
-        }
-
-        $resumeToken = is_array($document)
-            ? (isset($document['_id']) ? $document['_id'] : null)
-            : (isset($document->_id) ? $document->_id : null);
-
-        if ( ! isset($resumeToken)) {
-            throw ResumeTokenException::notFound();
-        }
-
-        if ( ! is_array($resumeToken) && ! is_object($resumeToken)) {
-            throw ResumeTokenException::invalidType($resumeToken);
-        }
-
-        return $resumeToken;
+        return $this->iterator->valid();
     }
 
     /**
@@ -203,11 +176,15 @@ class ChangeStream implements Iterator
             return true;
         }
 
-        if ( ! $exception instanceof ServerException) {
+        if (! $exception instanceof ServerException) {
             return false;
         }
 
-        if (in_array($exception->getCode(), [self::$errorCodeCappedPositionLost, self::$errorCodeCursorKilled, self::$errorCodeInterrupted])) {
+        if ($exception->hasErrorLabel('NonResumableChangeStreamError')) {
+            return false;
+        }
+
+        if (in_array($exception->getCode(), self::$nonResumableErrorCodes)) {
             return false;
         }
 
@@ -215,14 +192,63 @@ class ChangeStream implements Iterator
     }
 
     /**
-     * Creates a new changeStream after a resumable server error.
+     * Perform housekeeping after an iteration event.
+     *
+     * @param boolean $incrementKey Increment $key if there is a current result
+     * @throws ResumeTokenException
+     */
+    private function onIteration($incrementKey)
+    {
+        /* If the cursorId is 0, the server has invalidated the cursor and we
+         * will never perform another getMore nor need to resume since any
+         * remaining results (up to and including the invalidate event) will
+         * have been received in the last response. Therefore, we can unset the
+         * resumeCallable. This will free any reference to Watch as well as the
+         * only reference to any implicit session created therein. */
+        if ((string) $this->getCursorId() === '0') {
+            $this->resumeCallable = null;
+        }
+
+        /* Return early if there is not a current result. Avoid any attempt to
+         * increment the iterator's key. */
+        if (! $this->valid()) {
+            return;
+        }
+
+        if ($incrementKey) {
+            $this->key++;
+        }
+
+        $this->hasAdvanced = true;
+    }
+
+    /**
+     * Recreates the ChangeStreamIterator after a resumable server error.
      *
      * @return void
      */
     private function resume()
     {
-        $newChangeStream = call_user_func($this->resumeCallable, $this->resumeToken);
-        $this->csIt = $newChangeStream->csIt;
-        $this->csIt->rewind();
+        $this->iterator = call_user_func($this->resumeCallable, $this->getResumeToken(), $this->hasAdvanced);
+        $this->iterator->rewind();
+
+        $this->onIteration($this->hasAdvanced);
+    }
+
+    /**
+     * Either resumes after a resumable error or re-throws the exception.
+     *
+     * @param RuntimeException $exception
+     * @throws RuntimeException
+     */
+    private function resumeOrThrow(RuntimeException $exception)
+    {
+        if ($this->isResumableError($exception)) {
+            $this->resume();
+
+            return;
+        }
+
+        throw $exception;
     }
 }
diff --git a/cache/stores/mongodb/MongoDB/Client.php b/cache/stores/mongodb/MongoDB/Client.php
index be26ec5d04d..20310802d07 100644
--- a/cache/stores/mongodb/MongoDB/Client.php
+++ b/cache/stores/mongodb/MongoDB/Client.php
@@ -17,35 +17,55 @@
 
 namespace MongoDB;
 
+use MongoDB\Driver\Exception\InvalidArgumentException as DriverInvalidArgumentException;
+use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
 use MongoDB\Driver\Manager;
 use MongoDB\Driver\ReadConcern;
 use MongoDB\Driver\ReadPreference;
+use MongoDB\Driver\Session;
 use MongoDB\Driver\WriteConcern;
-use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
-use MongoDB\Driver\Exception\InvalidArgumentException as DriverInvalidArgumentException;
 use MongoDB\Exception\InvalidArgumentException;
 use MongoDB\Exception\UnexpectedValueException;
 use MongoDB\Exception\UnsupportedException;
+use MongoDB\Model\BSONArray;
+use MongoDB\Model\BSONDocument;
 use MongoDB\Model\DatabaseInfoIterator;
 use MongoDB\Operation\DropDatabase;
 use MongoDB\Operation\ListDatabases;
 use MongoDB\Operation\Watch;
+use function is_array;
 
 class Client
 {
+    /** @var array */
     private static $defaultTypeMap = [
-        'array' => 'MongoDB\Model\BSONArray',
-        'document' => 'MongoDB\Model\BSONDocument',
-        'root' => 'MongoDB\Model\BSONDocument',
+        'array' => BSONArray::class,
+        'document' => BSONDocument::class,
+        'root' => BSONDocument::class,
     ];
+
+    /** @var integer */
     private static $wireVersionForReadConcern = 4;
+
+    /** @var integer */
     private static $wireVersionForWritableCommandWriteConcern = 5;
 
+    /** @var Manager */
     private $manager;
+
+    /** @var ReadConcern */
     private $readConcern;
+
+    /** @var ReadPreference */
     private $readPreference;
+
+    /** @var string */
     private $uri;
+
+    /** @var array */
     private $typeMap;
+
+    /** @var WriteConcern */
     private $writeConcern;
 
     /**
@@ -146,13 +166,13 @@ class Client
      */
     public function dropDatabase($databaseName, array $options = [])
     {
-        if ( ! isset($options['typeMap'])) {
+        if (! isset($options['typeMap'])) {
             $options['typeMap'] = $this->typeMap;
         }
 
-        $server = $this->manager->selectServer(new ReadPreference(ReadPreference::RP_PRIMARY));
+        $server = select_server($this->manager, $options);
 
-        if ( ! isset($options['writeConcern']) && \MongoDB\server_supports_feature($server, self::$wireVersionForWritableCommandWriteConcern)) {
+        if (! isset($options['writeConcern']) && server_supports_feature($server, self::$wireVersionForWritableCommandWriteConcern) && ! is_in_transaction($options)) {
             $options['writeConcern'] = $this->writeConcern;
         }
 
@@ -217,6 +237,7 @@ class Client
      * List databases.
      *
      * @see ListDatabases::__construct() for supported options
+     * @param array $options
      * @return DatabaseInfoIterator
      * @throws UnexpectedValueException if the command response was malformed
      * @throws InvalidArgumentException for parameter/option parsing errors
@@ -225,7 +246,7 @@ class Client
     public function listDatabases(array $options = [])
     {
         $operation = new ListDatabases($options);
-        $server = $this->manager->selectServer(new ReadPreference(ReadPreference::RP_PRIMARY));
+        $server = select_server($this->manager, $options);
 
         return $operation->execute($server);
     }
@@ -267,8 +288,8 @@ class Client
      * Start a new client session.
      *
      * @see http://php.net/manual/en/mongodb-driver-manager.startsession.php
-     * @param array  $options      Session options
-     * @return MongoDB\Driver\Session
+     * @param array $options Session options
+     * @return Session
      */
     public function startSession(array $options = [])
     {
@@ -286,17 +307,17 @@ class Client
      */
     public function watch(array $pipeline = [], array $options = [])
     {
-        if ( ! isset($options['readPreference'])) {
+        if (! isset($options['readPreference']) && ! is_in_transaction($options)) {
             $options['readPreference'] = $this->readPreference;
         }
 
-        $server = $this->manager->selectServer($options['readPreference']);
+        $server = select_server($this->manager, $options);
 
-        if ( ! isset($options['readConcern']) && \MongoDB\server_supports_feature($server, self::$wireVersionForReadConcern)) {
+        if (! isset($options['readConcern']) && server_supports_feature($server, self::$wireVersionForReadConcern) && ! is_in_transaction($options)) {
             $options['readConcern'] = $this->readConcern;
         }
 
-        if ( ! isset($options['typeMap'])) {
+        if (! isset($options['typeMap'])) {
             $options['typeMap'] = $this->typeMap;
         }
 
diff --git a/cache/stores/mongodb/MongoDB/Collection.php b/cache/stores/mongodb/MongoDB/Collection.php
index 769e8353cea..82386445b98 100644
--- a/cache/stores/mongodb/MongoDB/Collection.php
+++ b/cache/stores/mongodb/MongoDB/Collection.php
@@ -18,24 +18,24 @@
 namespace MongoDB;
 
 use MongoDB\BSON\JavascriptInterface;
-use MongoDB\BSON\Serializable;
-use MongoDB\ChangeStream;
 use MongoDB\Driver\Cursor;
+use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
 use MongoDB\Driver\Manager;
 use MongoDB\Driver\ReadConcern;
 use MongoDB\Driver\ReadPreference;
 use MongoDB\Driver\WriteConcern;
-use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
 use MongoDB\Exception\InvalidArgumentException;
 use MongoDB\Exception\UnexpectedValueException;
 use MongoDB\Exception\UnsupportedException;
+use MongoDB\Model\BSONArray;
+use MongoDB\Model\BSONDocument;
 use MongoDB\Model\IndexInfo;
 use MongoDB\Model\IndexInfoIterator;
 use MongoDB\Operation\Aggregate;
 use MongoDB\Operation\BulkWrite;
-use MongoDB\Operation\CreateIndexes;
 use MongoDB\Operation\Count;
 use MongoDB\Operation\CountDocuments;
+use MongoDB\Operation\CreateIndexes;
 use MongoDB\Operation\DeleteMany;
 use MongoDB\Operation\DeleteOne;
 use MongoDB\Operation\Distinct;
@@ -58,24 +58,52 @@ use MongoDB\Operation\UpdateMany;
 use MongoDB\Operation\UpdateOne;
 use MongoDB\Operation\Watch;
 use Traversable;
+use function array_diff_key;
+use function array_intersect_key;
+use function current;
+use function is_array;
+use function strlen;
 
 class Collection
 {
+    /** @var array */
     private static $defaultTypeMap = [
-        'array' => 'MongoDB\Model\BSONArray',
-        'document' => 'MongoDB\Model\BSONDocument',
-        'root' => 'MongoDB\Model\BSONDocument',
+        'array' => BSONArray::class,
+        'document' => BSONDocument::class,
+        'root' => BSONDocument::class,
     ];
+
+    /** @var integer */
     private static $wireVersionForFindAndModifyWriteConcern = 4;
+
+    /** @var integer */
     private static $wireVersionForReadConcern = 4;
+
+    /** @var integer */
     private static $wireVersionForWritableCommandWriteConcern = 5;
 
+    /** @var integer */
+    private static $wireVersionForReadConcernWithWriteStage = 8;
+
+    /** @var string */
     private $collectionName;
+
+    /** @var string */
     private $databaseName;
+
+    /** @var Manager */
     private $manager;
+
+    /** @var ReadConcern */
     private $readConcern;
+
+    /** @var ReadPreference */
     private $readPreference;
+
+    /** @var array */
     private $typeMap;
+
+    /** @var WriteConcern */
     private $writeConcern;
 
     /**
@@ -116,11 +144,11 @@ class Collection
         }
 
         if (isset($options['readConcern']) && ! $options['readConcern'] instanceof ReadConcern) {
-            throw InvalidArgumentException::invalidType('"readConcern" option', $options['readConcern'], 'MongoDB\Driver\ReadConcern');
+            throw InvalidArgumentException::invalidType('"readConcern" option', $options['readConcern'], ReadConcern::class);
         }
 
         if (isset($options['readPreference']) && ! $options['readPreference'] instanceof ReadPreference) {
-            throw InvalidArgumentException::invalidType('"readPreference" option', $options['readPreference'], 'MongoDB\Driver\ReadPreference');
+            throw InvalidArgumentException::invalidType('"readPreference" option', $options['readPreference'], ReadPreference::class);
         }
 
         if (isset($options['typeMap']) && ! is_array($options['typeMap'])) {
@@ -128,7 +156,7 @@ class Collection
         }
 
         if (isset($options['writeConcern']) && ! $options['writeConcern'] instanceof WriteConcern) {
-            throw InvalidArgumentException::invalidType('"writeConcern" option', $options['writeConcern'], 'MongoDB\Driver\WriteConcern');
+            throw InvalidArgumentException::invalidType('"writeConcern" option', $options['writeConcern'], WriteConcern::class);
         }
 
         $this->manager = $manager;
@@ -189,32 +217,39 @@ class Collection
      */
     public function aggregate(array $pipeline, array $options = [])
     {
-        $hasOutStage = \MongoDB\is_last_pipeline_operator_out($pipeline);
+        $hasWriteStage = is_last_pipeline_operator_write($pipeline);
 
-        if ( ! isset($options['readPreference'])) {
+        if (! isset($options['readPreference']) && ! is_in_transaction($options)) {
             $options['readPreference'] = $this->readPreference;
         }
 
-        if ($hasOutStage) {
+        if ($hasWriteStage) {
             $options['readPreference'] = new ReadPreference(ReadPreference::RP_PRIMARY);
         }
 
-        $server = $this->manager->selectServer($options['readPreference']);
+        $server = select_server($this->manager, $options);
 
-        /* A "majority" read concern is not compatible with the $out stage, so
-         * avoid providing the Collection's read concern if it would conflict.
+        /* MongoDB 4.2 and later supports a read concern when an $out stage is
+         * being used, but earlier versions do not.
+         *
+         * A read concern is also not compatible with transactions.
          */
-        if ( ! isset($options['readConcern']) &&
-             ! ($hasOutStage && $this->readConcern->getLevel() === ReadConcern::MAJORITY) &&
-            \MongoDB\server_supports_feature($server, self::$wireVersionForReadConcern)) {
+        if (! isset($options['readConcern']) &&
+            server_supports_feature($server, self::$wireVersionForReadConcern) &&
+            ! is_in_transaction($options) &&
+            ( ! $hasWriteStage || server_supports_feature($server, self::$wireVersionForReadConcernWithWriteStage))
+        ) {
             $options['readConcern'] = $this->readConcern;
         }
 
-        if ( ! isset($options['typeMap'])) {
+        if (! isset($options['typeMap'])) {
             $options['typeMap'] = $this->typeMap;
         }
 
-        if ($hasOutStage && ! isset($options['writeConcern']) && \MongoDB\server_supports_feature($server, self::$wireVersionForWritableCommandWriteConcern)) {
+        if ($hasWriteStage &&
+            ! isset($options['writeConcern']) &&
+            server_supports_feature($server, self::$wireVersionForWritableCommandWriteConcern) &&
+            ! is_in_transaction($options)) {
             $options['writeConcern'] = $this->writeConcern;
         }
 
@@ -236,12 +271,12 @@ class Collection
      */
     public function bulkWrite(array $operations, array $options = [])
     {
-        if ( ! isset($options['writeConcern'])) {
+        if (! isset($options['writeConcern']) && ! is_in_transaction($options)) {
             $options['writeConcern'] = $this->writeConcern;
         }
 
         $operation = new BulkWrite($this->databaseName, $this->collectionName, $operations, $options);
-        $server = $this->manager->selectServer(new ReadPreference(ReadPreference::RP_PRIMARY));
+        $server = select_server($this->manager, $options);
 
         return $operation->execute($server);
     }
@@ -262,13 +297,13 @@ class Collection
      */
     public function count($filter = [], array $options = [])
     {
-        if ( ! isset($options['readPreference'])) {
+        if (! isset($options['readPreference']) && ! is_in_transaction($options)) {
             $options['readPreference'] = $this->readPreference;
         }
 
-        $server = $this->manager->selectServer($options['readPreference']);
+        $server = select_server($this->manager, $options);
 
-        if ( ! isset($options['readConcern']) && \MongoDB\server_supports_feature($server, self::$wireVersionForReadConcern)) {
+        if (! isset($options['readConcern']) && server_supports_feature($server, self::$wireVersionForReadConcern) && ! is_in_transaction($options)) {
             $options['readConcern'] = $this->readConcern;
         }
 
@@ -291,13 +326,13 @@ class Collection
      */
     public function countDocuments($filter = [], array $options = [])
     {
-        if ( ! isset($options['readPreference'])) {
+        if (! isset($options['readPreference']) && ! is_in_transaction($options)) {
             $options['readPreference'] = $this->readPreference;
         }
 
-        $server = $this->manager->selectServer($options['readPreference']);
+        $server = select_server($this->manager, $options);
 
-        if ( ! isset($options['readConcern']) && \MongoDB\server_supports_feature($server, self::$wireVersionForReadConcern)) {
+        if (! isset($options['readConcern']) && server_supports_feature($server, self::$wireVersionForReadConcern) && ! is_in_transaction($options)) {
             $options['readConcern'] = $this->readConcern;
         }
 
@@ -357,9 +392,9 @@ class Collection
      */
     public function createIndexes(array $indexes, array $options = [])
     {
-        $server = $this->manager->selectServer(new ReadPreference(ReadPreference::RP_PRIMARY));
+        $server = select_server($this->manager, $options);
 
-        if ( ! isset($options['writeConcern']) && \MongoDB\server_supports_feature($server, self::$wireVersionForWritableCommandWriteConcern)) {
+        if (! isset($options['writeConcern']) && server_supports_feature($server, self::$wireVersionForWritableCommandWriteConcern) && ! is_in_transaction($options)) {
             $options['writeConcern'] = $this->writeConcern;
         }
 
@@ -382,12 +417,12 @@ class Collection
      */
     public function deleteMany($filter, array $options = [])
     {
-        if ( ! isset($options['writeConcern'])) {
+        if (! isset($options['writeConcern']) && ! is_in_transaction($options)) {
             $options['writeConcern'] = $this->writeConcern;
         }
 
         $operation = new DeleteMany($this->databaseName, $this->collectionName, $filter, $options);
-        $server = $this->manager->selectServer(new ReadPreference(ReadPreference::RP_PRIMARY));
+        $server = select_server($this->manager, $options);
 
         return $operation->execute($server);
     }
@@ -406,12 +441,12 @@ class Collection
      */
     public function deleteOne($filter, array $options = [])
     {
-        if ( ! isset($options['writeConcern'])) {
+        if (! isset($options['writeConcern']) && ! is_in_transaction($options)) {
             $options['writeConcern'] = $this->writeConcern;
         }
 
         $operation = new DeleteOne($this->databaseName, $this->collectionName, $filter, $options);
-        $server = $this->manager->selectServer(new ReadPreference(ReadPreference::RP_PRIMARY));
+        $server = select_server($this->manager, $options);
 
         return $operation->execute($server);
     }
@@ -420,9 +455,9 @@ class Collection
      * Finds the distinct values for a specified field across the collection.
      *
      * @see Distinct::__construct() for supported options
-     * @param string $fieldName Field for which to return distinct values
-     * @param array|object $filter  Query by which to filter documents
-     * @param array        $options Command options
+     * @param string       $fieldName Field for which to return distinct values
+     * @param array|object $filter    Query by which to filter documents
+     * @param array        $options   Command options
      * @return mixed[]
      * @throws UnexpectedValueException if the command response was malformed
      * @throws UnsupportedException if options are not supported by the selected server
@@ -431,13 +466,17 @@ class Collection
      */
     public function distinct($fieldName, $filter = [], array $options = [])
     {
-        if ( ! isset($options['readPreference'])) {
+        if (! isset($options['readPreference']) && ! is_in_transaction($options)) {
             $options['readPreference'] = $this->readPreference;
         }
 
-        $server = $this->manager->selectServer($options['readPreference']);
+        if (! isset($options['typeMap'])) {
+            $options['typeMap'] = $this->typeMap;
+        }
 
-        if ( ! isset($options['readConcern']) && \MongoDB\server_supports_feature($server, self::$wireVersionForReadConcern)) {
+        $server = select_server($this->manager, $options);
+
+        if (! isset($options['readConcern']) && server_supports_feature($server, self::$wireVersionForReadConcern) && ! is_in_transaction($options)) {
             $options['readConcern'] = $this->readConcern;
         }
 
@@ -458,13 +497,13 @@ class Collection
      */
     public function drop(array $options = [])
     {
-        if ( ! isset($options['typeMap'])) {
+        if (! isset($options['typeMap'])) {
             $options['typeMap'] = $this->typeMap;
         }
 
-        $server = $this->manager->selectServer(new ReadPreference(ReadPreference::RP_PRIMARY));
+        $server = select_server($this->manager, $options);
 
-        if ( ! isset($options['writeConcern']) && \MongoDB\server_supports_feature($server, self::$wireVersionForWritableCommandWriteConcern)) {
+        if (! isset($options['writeConcern']) && server_supports_feature($server, self::$wireVersionForWritableCommandWriteConcern) && ! is_in_transaction($options)) {
             $options['writeConcern'] = $this->writeConcern;
         }
 
@@ -478,7 +517,7 @@ class Collection
      *
      * @see DropIndexes::__construct() for supported options
      * @param string|IndexInfo $indexName Index name or model object
-     * @param array  $options   Additional options
+     * @param array            $options   Additional options
      * @return array|object Command result document
      * @throws UnsupportedException if options are not supported by the selected server
      * @throws InvalidArgumentException for parameter/option parsing errors
@@ -492,13 +531,13 @@ class Collection
             throw new InvalidArgumentException('dropIndexes() must be used to drop multiple indexes');
         }
 
-        if ( ! isset($options['typeMap'])) {
+        if (! isset($options['typeMap'])) {
             $options['typeMap'] = $this->typeMap;
         }
 
-        $server = $this->manager->selectServer(new ReadPreference(ReadPreference::RP_PRIMARY));
+        $server = select_server($this->manager, $options);
 
-        if ( ! isset($options['writeConcern']) && \MongoDB\server_supports_feature($server, self::$wireVersionForWritableCommandWriteConcern)) {
+        if (! isset($options['writeConcern']) && server_supports_feature($server, self::$wireVersionForWritableCommandWriteConcern) && ! is_in_transaction($options)) {
             $options['writeConcern'] = $this->writeConcern;
         }
 
@@ -519,13 +558,13 @@ class Collection
      */
     public function dropIndexes(array $options = [])
     {
-        if ( ! isset($options['typeMap'])) {
+        if (! isset($options['typeMap'])) {
             $options['typeMap'] = $this->typeMap;
         }
 
-        $server = $this->manager->selectServer(new ReadPreference(ReadPreference::RP_PRIMARY));
+        $server = select_server($this->manager, $options);
 
-        if ( ! isset($options['writeConcern']) && \MongoDB\server_supports_feature($server, self::$wireVersionForWritableCommandWriteConcern)) {
+        if (! isset($options['writeConcern']) && server_supports_feature($server, self::$wireVersionForWritableCommandWriteConcern) && ! is_in_transaction($options)) {
             $options['writeConcern'] = $this->writeConcern;
         }
 
@@ -545,15 +584,15 @@ class Collection
      * @throws InvalidArgumentException for parameter/option parsing errors
      * @throws DriverRuntimeException for other driver errors (e.g. connection errors)
      */
-    public function EstimatedDocumentCount(array $options = [])
+    public function estimatedDocumentCount(array $options = [])
     {
-        if ( ! isset($options['readPreference'])) {
+        if (! isset($options['readPreference']) && ! is_in_transaction($options)) {
             $options['readPreference'] = $this->readPreference;
         }
 
-        $server = $this->manager->selectServer($options['readPreference']);
+        $server = select_server($this->manager, $options);
 
-        if ( ! isset($options['readConcern']) && \MongoDB\server_supports_feature($server, self::$wireVersionForReadConcern)) {
+        if (! isset($options['readConcern']) && server_supports_feature($server, self::$wireVersionForReadConcern) && ! is_in_transaction($options)) {
             $options['readConcern'] = $this->readConcern;
         }
 
@@ -567,8 +606,8 @@ class Collection
      *
      * @see Explain::__construct() for supported options
      * @see http://docs.mongodb.org/manual/reference/command/explain/
-     * @param Explainable $explainable  Command on which to run explain
-     * @param array       $options      Additional options
+     * @param Explainable $explainable Command on which to run explain
+     * @param array       $options     Additional options
      * @return array|object
      * @throws UnsupportedException if explainable or options are not supported by the selected server
      * @throws InvalidArgumentException for parameter/option parsing errors
@@ -576,15 +615,15 @@ class Collection
      */
     public function explain(Explainable $explainable, array $options = [])
     {
-        if ( ! isset($options['readPreference'])) {
+        if (! isset($options['readPreference']) && ! is_in_transaction($options)) {
             $options['readPreference'] = $this->readPreference;
         }
 
-        if ( ! isset($options['typeMap'])) {
+        if (! isset($options['typeMap'])) {
             $options['typeMap'] = $this->typeMap;
         }
 
-        $server = $this->manager->selectServer($options['readPreference']);
+        $server = select_server($this->manager, $options);
 
         $operation = new Explain($this->databaseName, $explainable, $options);
 
@@ -605,17 +644,17 @@ class Collection
      */
     public function find($filter = [], array $options = [])
     {
-        if ( ! isset($options['readPreference'])) {
+        if (! isset($options['readPreference']) && ! is_in_transaction($options)) {
             $options['readPreference'] = $this->readPreference;
         }
 
-        $server = $this->manager->selectServer($options['readPreference']);
+        $server = select_server($this->manager, $options);
 
-        if ( ! isset($options['readConcern']) && \MongoDB\server_supports_feature($server, self::$wireVersionForReadConcern)) {
+        if (! isset($options['readConcern']) && server_supports_feature($server, self::$wireVersionForReadConcern) && ! is_in_transaction($options)) {
             $options['readConcern'] = $this->readConcern;
         }
 
-        if ( ! isset($options['typeMap'])) {
+        if (! isset($options['typeMap'])) {
             $options['typeMap'] = $this->typeMap;
         }
 
@@ -638,17 +677,17 @@ class Collection
      */
     public function findOne($filter = [], array $options = [])
     {
-        if ( ! isset($options['readPreference'])) {
+        if (! isset($options['readPreference']) && ! is_in_transaction($options)) {
             $options['readPreference'] = $this->readPreference;
         }
 
-        $server = $this->manager->selectServer($options['readPreference']);
+        $server = select_server($this->manager, $options);
 
-        if ( ! isset($options['readConcern']) && \MongoDB\server_supports_feature($server, self::$wireVersionForReadConcern)) {
+        if (! isset($options['readConcern']) && server_supports_feature($server, self::$wireVersionForReadConcern) && ! is_in_transaction($options)) {
             $options['readConcern'] = $this->readConcern;
         }
 
-        if ( ! isset($options['typeMap'])) {
+        if (! isset($options['typeMap'])) {
             $options['typeMap'] = $this->typeMap;
         }
 
@@ -674,13 +713,13 @@ class Collection
      */
     public function findOneAndDelete($filter, array $options = [])
     {
-        $server = $this->manager->selectServer(new ReadPreference(ReadPreference::RP_PRIMARY));
+        $server = select_server($this->manager, $options);
 
-        if ( ! isset($options['writeConcern']) && \MongoDB\server_supports_feature($server, self::$wireVersionForFindAndModifyWriteConcern)) {
+        if (! isset($options['writeConcern']) && server_supports_feature($server, self::$wireVersionForFindAndModifyWriteConcern) && ! is_in_transaction($options)) {
             $options['writeConcern'] = $this->writeConcern;
         }
 
-        if ( ! isset($options['typeMap'])) {
+        if (! isset($options['typeMap'])) {
             $options['typeMap'] = $this->typeMap;
         }
 
@@ -711,13 +750,13 @@ class Collection
      */
     public function findOneAndReplace($filter, $replacement, array $options = [])
     {
-        $server = $this->manager->selectServer(new ReadPreference(ReadPreference::RP_PRIMARY));
+        $server = select_server($this->manager, $options);
 
-        if ( ! isset($options['writeConcern']) && \MongoDB\server_supports_feature($server, self::$wireVersionForFindAndModifyWriteConcern)) {
+        if (! isset($options['writeConcern']) && server_supports_feature($server, self::$wireVersionForFindAndModifyWriteConcern) && ! is_in_transaction($options)) {
             $options['writeConcern'] = $this->writeConcern;
         }
 
-        if ( ! isset($options['typeMap'])) {
+        if (! isset($options['typeMap'])) {
             $options['typeMap'] = $this->typeMap;
         }
 
@@ -748,13 +787,13 @@ class Collection
      */
     public function findOneAndUpdate($filter, $update, array $options = [])
     {
-        $server = $this->manager->selectServer(new ReadPreference(ReadPreference::RP_PRIMARY));
+        $server = select_server($this->manager, $options);
 
-        if ( ! isset($options['writeConcern']) && \MongoDB\server_supports_feature($server, self::$wireVersionForFindAndModifyWriteConcern)) {
+        if (! isset($options['writeConcern']) && server_supports_feature($server, self::$wireVersionForFindAndModifyWriteConcern) && ! is_in_transaction($options)) {
             $options['writeConcern'] = $this->writeConcern;
         }
 
-        if ( ! isset($options['typeMap'])) {
+        if (! isset($options['typeMap'])) {
             $options['typeMap'] = $this->typeMap;
         }
 
@@ -859,12 +898,12 @@ class Collection
      */
     public function insertMany(array $documents, array $options = [])
     {
-        if ( ! isset($options['writeConcern'])) {
+        if (! isset($options['writeConcern']) && ! is_in_transaction($options)) {
             $options['writeConcern'] = $this->writeConcern;
         }
 
         $operation = new InsertMany($this->databaseName, $this->collectionName, $documents, $options);
-        $server = $this->manager->selectServer(new ReadPreference(ReadPreference::RP_PRIMARY));
+        $server = select_server($this->manager, $options);
 
         return $operation->execute($server);
     }
@@ -882,12 +921,12 @@ class Collection
      */
     public function insertOne($document, array $options = [])
     {
-        if ( ! isset($options['writeConcern'])) {
+        if (! isset($options['writeConcern']) && ! is_in_transaction($options)) {
             $options['writeConcern'] = $this->writeConcern;
         }
 
         $operation = new InsertOne($this->databaseName, $this->collectionName, $document, $options);
-        $server = $this->manager->selectServer(new ReadPreference(ReadPreference::RP_PRIMARY));
+        $server = select_server($this->manager, $options);
 
         return $operation->execute($server);
     }
@@ -896,6 +935,7 @@ class Collection
      * Returns information for all indexes for the collection.
      *
      * @see ListIndexes::__construct() for supported options
+     * @param array $options
      * @return IndexInfoIterator
      * @throws InvalidArgumentException for parameter/option parsing errors
      * @throws DriverRuntimeException for other driver errors (e.g. connection errors)
@@ -903,7 +943,7 @@ class Collection
     public function listIndexes(array $options = [])
     {
         $operation = new ListIndexes($this->databaseName, $this->collectionName, $options);
-        $server = $this->manager->selectServer(new ReadPreference(ReadPreference::RP_PRIMARY));
+        $server = select_server($this->manager, $options);
 
         return $operation->execute($server);
     }
@@ -913,10 +953,10 @@ class Collection
      *
      * @see MapReduce::__construct() for supported options
      * @see http://docs.mongodb.org/manual/reference/command/mapReduce/
-     * @param JavascriptInterface $map            Map function
-     * @param JavascriptInterface $reduce         Reduce function
-     * @param string|array|object $out            Output specification
-     * @param array               $options        Command options
+     * @param JavascriptInterface $map     Map function
+     * @param JavascriptInterface $reduce  Reduce function
+     * @param string|array|object $out     Output specification
+     * @param array               $options Command options
      * @return MapReduceResult
      * @throws UnsupportedException if options are not supported by the selected server
      * @throws InvalidArgumentException for parameter/option parsing errors
@@ -925,9 +965,9 @@ class Collection
      */
     public function mapReduce(JavascriptInterface $map, JavascriptInterface $reduce, $out, array $options = [])
     {
-        $hasOutputCollection = ! \MongoDB\is_mapreduce_output_inline($out);
+        $hasOutputCollection = ! is_mapreduce_output_inline($out);
 
-        if ( ! isset($options['readPreference'])) {
+        if (! isset($options['readPreference']) && ! is_in_transaction($options)) {
             $options['readPreference'] = $this->readPreference;
         }
 
@@ -936,20 +976,22 @@ class Collection
             $options['readPreference'] = new ReadPreference(ReadPreference::RP_PRIMARY);
         }
 
-        $server = $this->manager->selectServer($options['readPreference']);
+        $server = select_server($this->manager, $options);
 
         /* A "majority" read concern is not compatible with inline output, so
          * avoid providing the Collection's read concern if it would conflict.
+         *
+         * A read concern is also not compatible with transactions.
          */
-        if ( ! isset($options['readConcern']) && ! ($hasOutputCollection && $this->readConcern->getLevel() === ReadConcern::MAJORITY) && \MongoDB\server_supports_feature($server, self::$wireVersionForReadConcern)) {
+        if (! isset($options['readConcern']) && ! ($hasOutputCollection && $this->readConcern->getLevel() === ReadConcern::MAJORITY) && server_supports_feature($server, self::$wireVersionForReadConcern) && ! is_in_transaction($options)) {
             $options['readConcern'] = $this->readConcern;
         }
 
-        if ( ! isset($options['typeMap'])) {
+        if (! isset($options['typeMap'])) {
             $options['typeMap'] = $this->typeMap;
         }
 
-        if ( ! isset($options['writeConcern']) && \MongoDB\server_supports_feature($server, self::$wireVersionForWritableCommandWriteConcern)) {
+        if (! isset($options['writeConcern']) && server_supports_feature($server, self::$wireVersionForWritableCommandWriteConcern) && ! is_in_transaction($options)) {
             $options['writeConcern'] = $this->writeConcern;
         }
 
@@ -973,12 +1015,12 @@ class Collection
      */
     public function replaceOne($filter, $replacement, array $options = [])
     {
-        if ( ! isset($options['writeConcern'])) {
+        if (! isset($options['writeConcern']) && ! is_in_transaction($options)) {
             $options['writeConcern'] = $this->writeConcern;
         }
 
         $operation = new ReplaceOne($this->databaseName, $this->collectionName, $filter, $replacement, $options);
-        $server = $this->manager->selectServer(new ReadPreference(ReadPreference::RP_PRIMARY));
+        $server = select_server($this->manager, $options);
 
         return $operation->execute($server);
     }
@@ -998,12 +1040,12 @@ class Collection
      */
     public function updateMany($filter, $update, array $options = [])
     {
-        if ( ! isset($options['writeConcern'])) {
+        if (! isset($options['writeConcern']) && ! is_in_transaction($options)) {
             $options['writeConcern'] = $this->writeConcern;
         }
 
         $operation = new UpdateMany($this->databaseName, $this->collectionName, $filter, $update, $options);
-        $server = $this->manager->selectServer(new ReadPreference(ReadPreference::RP_PRIMARY));
+        $server = select_server($this->manager, $options);
 
         return $operation->execute($server);
     }
@@ -1023,12 +1065,12 @@ class Collection
      */
     public function updateOne($filter, $update, array $options = [])
     {
-        if ( ! isset($options['writeConcern'])) {
+        if (! isset($options['writeConcern']) && ! is_in_transaction($options)) {
             $options['writeConcern'] = $this->writeConcern;
         }
 
         $operation = new UpdateOne($this->databaseName, $this->collectionName, $filter, $update, $options);
-        $server = $this->manager->selectServer(new ReadPreference(ReadPreference::RP_PRIMARY));
+        $server = select_server($this->manager, $options);
 
         return $operation->execute($server);
     }
@@ -1044,11 +1086,11 @@ class Collection
      */
     public function watch(array $pipeline = [], array $options = [])
     {
-        if ( ! isset($options['readPreference'])) {
+        if (! isset($options['readPreference']) && ! is_in_transaction($options)) {
             $options['readPreference'] = $this->readPreference;
         }
 
-        $server = $this->manager->selectServer($options['readPreference']);
+        $server = select_server($this->manager, $options);
 
         /* Although change streams require a newer version of the server than
          * read concerns, perform the usual wire version check before inheriting
@@ -1057,11 +1099,11 @@ class Collection
          * related to change streams being unsupported instead of an
          * UnsupportedException regarding use of the "readConcern" option from
          * the Aggregate operation class. */
-        if ( ! isset($options['readConcern']) && \MongoDB\server_supports_feature($server, self::$wireVersionForReadConcern)) {
+        if (! isset($options['readConcern']) && server_supports_feature($server, self::$wireVersionForReadConcern) && ! is_in_transaction($options)) {
             $options['readConcern'] = $this->readConcern;
         }
 
-        if ( ! isset($options['typeMap'])) {
+        if (! isset($options['typeMap'])) {
             $options['typeMap'] = $this->typeMap;
         }
 
diff --git a/cache/stores/mongodb/MongoDB/Database.php b/cache/stores/mongodb/MongoDB/Database.php
index 3b8b0e711b3..323a69bfb34 100644
--- a/cache/stores/mongodb/MongoDB/Database.php
+++ b/cache/stores/mongodb/MongoDB/Database.php
@@ -17,17 +17,20 @@
 
 namespace MongoDB;
 
-use MongoDB\Collection;
 use MongoDB\Driver\Cursor;
+use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
 use MongoDB\Driver\Manager;
 use MongoDB\Driver\ReadConcern;
 use MongoDB\Driver\ReadPreference;
 use MongoDB\Driver\WriteConcern;
-use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
 use MongoDB\Exception\InvalidArgumentException;
+use MongoDB\Exception\UnexpectedValueException;
 use MongoDB\Exception\UnsupportedException;
 use MongoDB\GridFS\Bucket;
+use MongoDB\Model\BSONArray;
+use MongoDB\Model\BSONDocument;
 use MongoDB\Model\CollectionInfoIterator;
+use MongoDB\Operation\Aggregate;
 use MongoDB\Operation\CreateCollection;
 use MongoDB\Operation\DatabaseCommand;
 use MongoDB\Operation\DropCollection;
@@ -35,22 +38,44 @@ use MongoDB\Operation\DropDatabase;
 use MongoDB\Operation\ListCollections;
 use MongoDB\Operation\ModifyCollection;
 use MongoDB\Operation\Watch;
+use Traversable;
+use function is_array;
+use function strlen;
 
 class Database
 {
+    /** @var array */
     private static $defaultTypeMap = [
-        'array' => 'MongoDB\Model\BSONArray',
-        'document' => 'MongoDB\Model\BSONDocument',
-        'root' => 'MongoDB\Model\BSONDocument',
+        'array' => BSONArray::class,
+        'document' => BSONDocument::class,
+        'root' => BSONDocument::class,
     ];
+
+    /** @var integer */
     private static $wireVersionForReadConcern = 4;
+
+    /** @var integer */
     private static $wireVersionForWritableCommandWriteConcern = 5;
 
+    /** @var integer */
+    private static $wireVersionForReadConcernWithWriteStage = 8;
+
+    /** @var string */
     private $databaseName;
+
+    /** @var Manager */
     private $manager;
+
+    /** @var ReadConcern */
     private $readConcern;
+
+    /** @var ReadPreference */
     private $readPreference;
+
+    /** @var array */
     private $typeMap;
+
+    /** @var WriteConcern */
     private $writeConcern;
 
     /**
@@ -87,11 +112,11 @@ class Database
         }
 
         if (isset($options['readConcern']) && ! $options['readConcern'] instanceof ReadConcern) {
-            throw InvalidArgumentException::invalidType('"readConcern" option', $options['readConcern'], 'MongoDB\Driver\ReadConcern');
+            throw InvalidArgumentException::invalidType('"readConcern" option', $options['readConcern'], ReadConcern::class);
         }
 
         if (isset($options['readPreference']) && ! $options['readPreference'] instanceof ReadPreference) {
-            throw InvalidArgumentException::invalidType('"readPreference" option', $options['readPreference'], 'MongoDB\Driver\ReadPreference');
+            throw InvalidArgumentException::invalidType('"readPreference" option', $options['readPreference'], ReadPreference::class);
         }
 
         if (isset($options['typeMap']) && ! is_array($options['typeMap'])) {
@@ -99,7 +124,7 @@ class Database
         }
 
         if (isset($options['writeConcern']) && ! $options['writeConcern'] instanceof WriteConcern) {
-            throw InvalidArgumentException::invalidType('"writeConcern" option', $options['writeConcern'], 'MongoDB\Driver\WriteConcern');
+            throw InvalidArgumentException::invalidType('"writeConcern" option', $options['writeConcern'], WriteConcern::class);
         }
 
         $this->manager = $manager;
@@ -155,6 +180,63 @@ class Database
         return $this->databaseName;
     }
 
+    /**
+     * Runs an aggregation framework pipeline on the database for pipeline
+     * stages that do not require an underlying collection, such as $currentOp
+     * and $listLocalSessions. Requires MongoDB >= 3.6
+     *
+     * @see Aggregate::__construct() for supported options
+     * @param array $pipeline List of pipeline operations
+     * @param array $options  Command options
+     * @return Traversable
+     * @throws UnexpectedValueException if the command response was malformed
+     * @throws UnsupportedException if options are not supported by the selected server
+     * @throws InvalidArgumentException for parameter/option parsing errors
+     * @throws DriverRuntimeException for other driver errors (e.g. connection errors)
+     */
+    public function aggregate(array $pipeline, array $options = [])
+    {
+        $hasWriteStage = is_last_pipeline_operator_write($pipeline);
+
+        if (! isset($options['readPreference']) && ! is_in_transaction($options)) {
+            $options['readPreference'] = $this->readPreference;
+        }
+
+        if ($hasWriteStage) {
+            $options['readPreference'] = new ReadPreference(ReadPreference::RP_PRIMARY);
+        }
+
+        $server = select_server($this->manager, $options);
+
+        /* MongoDB 4.2 and later supports a read concern when an $out stage is
+         * being used, but earlier versions do not.
+         *
+         * A read concern is also not compatible with transactions.
+         */
+        if (! isset($options['readConcern']) &&
+            server_supports_feature($server, self::$wireVersionForReadConcern) &&
+            ! is_in_transaction($options) &&
+            ( ! $hasWriteStage || server_supports_feature($server, self::$wireVersionForReadConcernWithWriteStage))
+        ) {
+            $options['readConcern'] = $this->readConcern;
+        }
+
+        if (! isset($options['typeMap'])) {
+            $options['typeMap'] = $this->typeMap;
+        }
+
+        if ($hasWriteStage &&
+            ! isset($options['writeConcern']) &&
+            server_supports_feature($server, self::$wireVersionForWritableCommandWriteConcern) &&
+            ! is_in_transaction($options)) {
+            $options['writeConcern'] = $this->writeConcern;
+        }
+
+        $operation = new Aggregate($this->databaseName, null, $pipeline, $options);
+
+        return $operation->execute($server);
+    }
+
     /**
      * Execute a command on this database.
      *
@@ -167,16 +249,16 @@ class Database
      */
     public function command($command, array $options = [])
     {
-        if ( ! isset($options['readPreference'])) {
+        if (! isset($options['readPreference']) && ! is_in_transaction($options)) {
             $options['readPreference'] = $this->readPreference;
         }
 
-        if ( ! isset($options['typeMap'])) {
+        if (! isset($options['typeMap'])) {
             $options['typeMap'] = $this->typeMap;
         }
 
         $operation = new DatabaseCommand($this->databaseName, $command, $options);
-        $server = $this->manager->selectServer($options['readPreference']);
+        $server = select_server($this->manager, $options);
 
         return $operation->execute($server);
     }
@@ -194,13 +276,13 @@ class Database
      */
     public function createCollection($collectionName, array $options = [])
     {
-        if ( ! isset($options['typeMap'])) {
+        if (! isset($options['typeMap'])) {
             $options['typeMap'] = $this->typeMap;
         }
 
-        $server = $this->manager->selectServer(new ReadPreference(ReadPreference::RP_PRIMARY));
+        $server = select_server($this->manager, $options);
 
-        if ( ! isset($options['writeConcern']) && \MongoDB\server_supports_feature($server, self::$wireVersionForWritableCommandWriteConcern)) {
+        if (! isset($options['writeConcern']) && server_supports_feature($server, self::$wireVersionForWritableCommandWriteConcern) && ! is_in_transaction($options)) {
             $options['writeConcern'] = $this->writeConcern;
         }
 
@@ -221,13 +303,13 @@ class Database
      */
     public function drop(array $options = [])
     {
-        if ( ! isset($options['typeMap'])) {
+        if (! isset($options['typeMap'])) {
             $options['typeMap'] = $this->typeMap;
         }
 
-        $server = $this->manager->selectServer(new ReadPreference(ReadPreference::RP_PRIMARY));
+        $server = select_server($this->manager, $options);
 
-        if ( ! isset($options['writeConcern']) && \MongoDB\server_supports_feature($server, self::$wireVersionForWritableCommandWriteConcern)) {
+        if (! isset($options['writeConcern']) && server_supports_feature($server, self::$wireVersionForWritableCommandWriteConcern) && ! is_in_transaction($options)) {
             $options['writeConcern'] = $this->writeConcern;
         }
 
@@ -249,13 +331,13 @@ class Database
      */
     public function dropCollection($collectionName, array $options = [])
     {
-        if ( ! isset($options['typeMap'])) {
+        if (! isset($options['typeMap'])) {
             $options['typeMap'] = $this->typeMap;
         }
 
-        $server = $this->manager->selectServer(new ReadPreference(ReadPreference::RP_PRIMARY));
+        $server = select_server($this->manager, $options);
 
-        if ( ! isset($options['writeConcern']) && \MongoDB\server_supports_feature($server, self::$wireVersionForWritableCommandWriteConcern)) {
+        if (! isset($options['writeConcern']) && server_supports_feature($server, self::$wireVersionForWritableCommandWriteConcern) && ! is_in_transaction($options)) {
             $options['writeConcern'] = $this->writeConcern;
         }
 
@@ -338,7 +420,7 @@ class Database
     public function listCollections(array $options = [])
     {
         $operation = new ListCollections($this->databaseName, $options);
-        $server = $this->manager->selectServer(new ReadPreference(ReadPreference::RP_PRIMARY));
+        $server = select_server($this->manager, $options);
 
         return $operation->execute($server);
     }
@@ -350,18 +432,19 @@ class Database
      * @param string $collectionName    Collection or view to modify
      * @param array  $collectionOptions Collection or view options to assign
      * @param array  $options           Command options
+     * @return array|object
      * @throws InvalidArgumentException for parameter/option parsing errors
      * @throws DriverRuntimeException for other driver errors (e.g. connection errors)
      */
     public function modifyCollection($collectionName, array $collectionOptions, array $options = [])
     {
-        if ( ! isset($options['typeMap'])) {
+        if (! isset($options['typeMap'])) {
             $options['typeMap'] = $this->typeMap;
         }
 
-        $server = $this->manager->selectServer(new ReadPreference(ReadPreference::RP_PRIMARY));
+        $server = select_server($this->manager, $options);
 
-        if ( ! isset($options['writeConcern']) && \MongoDB\server_supports_feature($server, self::$wireVersionForWritableCommandWriteConcern)) {
+        if (! isset($options['writeConcern']) && server_supports_feature($server, self::$wireVersionForWritableCommandWriteConcern) && ! is_in_transaction($options)) {
             $options['writeConcern'] = $this->writeConcern;
         }
 
@@ -422,17 +505,17 @@ class Database
      */
     public function watch(array $pipeline = [], array $options = [])
     {
-        if ( ! isset($options['readPreference'])) {
+        if (! isset($options['readPreference']) && ! is_in_transaction($options)) {
             $options['readPreference'] = $this->readPreference;
         }
 
-        $server = $this->manager->selectServer($options['readPreference']);
+        $server = select_server($this->manager, $options);
 
-        if ( ! isset($options['readConcern']) && \MongoDB\server_supports_feature($server, self::$wireVersionForReadConcern)) {
+        if (! isset($options['readConcern']) && server_supports_feature($server, self::$wireVersionForReadConcern) && ! is_in_transaction($options)) {
             $options['readConcern'] = $this->readConcern;
         }
 
-        if ( ! isset($options['typeMap'])) {
+        if (! isset($options['typeMap'])) {
             $options['typeMap'] = $this->typeMap;
         }
 
diff --git a/cache/stores/mongodb/MongoDB/DeleteResult.php b/cache/stores/mongodb/MongoDB/DeleteResult.php
index a60137b32d5..c5b9ce64d42 100644
--- a/cache/stores/mongodb/MongoDB/DeleteResult.php
+++ b/cache/stores/mongodb/MongoDB/DeleteResult.php
@@ -25,14 +25,12 @@ use MongoDB\Exception\BadMethodCallException;
  */
 class DeleteResult
 {
+    /** @var WriteResult */
     private $writeResult;
+
+    /** @var boolean */
     private $isAcknowledged;
 
-    /**
-     * Constructor.
-     *
-     * @param WriteResult $writeResult
-     */
     public function __construct(WriteResult $writeResult)
     {
         $this->writeResult = $writeResult;
diff --git a/cache/stores/mongodb/MongoDB/Exception/BadMethodCallException.php b/cache/stores/mongodb/MongoDB/Exception/BadMethodCallException.php
index f1fe47af652..00cd79cf224 100644
--- a/cache/stores/mongodb/MongoDB/Exception/BadMethodCallException.php
+++ b/cache/stores/mongodb/MongoDB/Exception/BadMethodCallException.php
@@ -17,7 +17,10 @@
 
 namespace MongoDB\Exception;
 
-class BadMethodCallException extends \BadMethodCallException implements Exception
+use BadMethodCallException as BaseBadMethodCallException;
+use function sprintf;
+
+class BadMethodCallException extends BaseBadMethodCallException implements Exception
 {
     /**
      * Thrown when a mutable method is invoked on an immutable object.
diff --git a/cache/stores/mongodb/MongoDB/Exception/Exception.php b/cache/stores/mongodb/MongoDB/Exception/Exception.php
index 703a44c7964..154a193915c 100644
--- a/cache/stores/mongodb/MongoDB/Exception/Exception.php
+++ b/cache/stores/mongodb/MongoDB/Exception/Exception.php
@@ -17,6 +17,8 @@
 
 namespace MongoDB\Exception;
 
-interface Exception extends \MongoDB\Driver\Exception\Exception
+use MongoDB\Driver\Exception\Exception as DriverException;
+
+interface Exception extends DriverException
 {
 }
diff --git a/cache/stores/mongodb/MongoDB/Exception/InvalidArgumentException.php b/cache/stores/mongodb/MongoDB/Exception/InvalidArgumentException.php
index 622215a6b16..e3b44478b27 100644
--- a/cache/stores/mongodb/MongoDB/Exception/InvalidArgumentException.php
+++ b/cache/stores/mongodb/MongoDB/Exception/InvalidArgumentException.php
@@ -17,7 +17,13 @@
 
 namespace MongoDB\Exception;
 
-class InvalidArgumentException extends \MongoDB\Driver\Exception\InvalidArgumentException implements Exception
+use MongoDB\Driver\Exception\InvalidArgumentException as DriverInvalidArgumentException;
+use function get_class;
+use function gettype;
+use function is_object;
+use function sprintf;
+
+class InvalidArgumentException extends DriverInvalidArgumentException implements Exception
 {
     /**
      * Thrown when an argument or option has an invalid type.
diff --git a/cache/stores/mongodb/MongoDB/Exception/ResumeTokenException.php b/cache/stores/mongodb/MongoDB/Exception/ResumeTokenException.php
index 4aeb6559268..20036470c7e 100644
--- a/cache/stores/mongodb/MongoDB/Exception/ResumeTokenException.php
+++ b/cache/stores/mongodb/MongoDB/Exception/ResumeTokenException.php
@@ -17,7 +17,10 @@
 
 namespace MongoDB\Exception;
 
-class ResumeTokenException extends \Exception
+use function gettype;
+use function sprintf;
+
+class ResumeTokenException extends RuntimeException
 {
     /**
      * Thrown when a resume token has an invalid type.
diff --git a/cache/stores/mongodb/MongoDB/Exception/RuntimeException.php b/cache/stores/mongodb/MongoDB/Exception/RuntimeException.php
index 4d8c0b8af3b..a64c0a4a41d 100644
--- a/cache/stores/mongodb/MongoDB/Exception/RuntimeException.php
+++ b/cache/stores/mongodb/MongoDB/Exception/RuntimeException.php
@@ -17,6 +17,8 @@
 
 namespace MongoDB\Exception;
 
-class RuntimeException extends \MongoDB\Driver\Exception\RuntimeException implements Exception
+use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
+
+class RuntimeException extends DriverRuntimeException implements Exception
 {
 }
diff --git a/cache/stores/mongodb/MongoDB/Exception/UnexpectedValueException.php b/cache/stores/mongodb/MongoDB/Exception/UnexpectedValueException.php
index a65eaa7ccf8..e91b36981f2 100644
--- a/cache/stores/mongodb/MongoDB/Exception/UnexpectedValueException.php
+++ b/cache/stores/mongodb/MongoDB/Exception/UnexpectedValueException.php
@@ -17,6 +17,8 @@
 
 namespace MongoDB\Exception;
 
-class UnexpectedValueException extends \MongoDB\Driver\Exception\UnexpectedValueException implements Exception
+use MongoDB\Driver\Exception\UnexpectedValueException as DriverUnexpectedValueException;
+
+class UnexpectedValueException extends DriverUnexpectedValueException implements Exception
 {
 }
diff --git a/cache/stores/mongodb/MongoDB/Exception/UnsupportedException.php b/cache/stores/mongodb/MongoDB/Exception/UnsupportedException.php
index 91f99b21469..918de9925d0 100644
--- a/cache/stores/mongodb/MongoDB/Exception/UnsupportedException.php
+++ b/cache/stores/mongodb/MongoDB/Exception/UnsupportedException.php
@@ -59,6 +59,16 @@ class UnsupportedException extends RuntimeException
         return new static('Read concern is not supported by the server executing this command');
     }
 
+    /**
+     * Thrown when a readConcern is used with a read operation in a transaction.
+     *
+     * @return self
+     */
+    public static function readConcernNotSupportedInTransaction()
+    {
+        return new static('The "readConcern" option cannot be specified within a transaction. Instead, specify it when starting the transaction.');
+    }
+
     /**
      * Thrown when a command's writeConcern option is not supported by a server.
      *
@@ -68,4 +78,14 @@ class UnsupportedException extends RuntimeException
     {
         return new static('Write concern is not supported by the server executing this command');
     }
+
+    /**
+     * Thrown when a writeConcern is used with a write operation in a transaction.
+     *
+     * @return self
+     */
+    public static function writeConcernNotSupportedInTransaction()
+    {
+        return new static('The "writeConcern" option cannot be specified within a transaction. Instead, specify it when starting the transaction.');
+    }
 }
diff --git a/cache/stores/mongodb/MongoDB/GridFS/Bucket.php b/cache/stores/mongodb/MongoDB/GridFS/Bucket.php
index 243c331ec74..dc1532ce8f3 100644
--- a/cache/stores/mongodb/MongoDB/GridFS/Bucket.php
+++ b/cache/stores/mongodb/MongoDB/GridFS/Bucket.php
@@ -19,16 +19,40 @@ namespace MongoDB\GridFS;
 
 use MongoDB\Collection;
 use MongoDB\Driver\Cursor;
+use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
 use MongoDB\Driver\Manager;
 use MongoDB\Driver\ReadConcern;
 use MongoDB\Driver\ReadPreference;
 use MongoDB\Driver\WriteConcern;
-use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
 use MongoDB\Exception\InvalidArgumentException;
+use MongoDB\Exception\UnsupportedException;
 use MongoDB\GridFS\Exception\CorruptFileException;
 use MongoDB\GridFS\Exception\FileNotFoundException;
+use MongoDB\Model\BSONArray;
+use MongoDB\Model\BSONDocument;
 use MongoDB\Operation\Find;
 use stdClass;
+use function array_intersect_key;
+use function fopen;
+use function get_resource_type;
+use function in_array;
+use function is_array;
+use function is_bool;
+use function is_integer;
+use function is_object;
+use function is_resource;
+use function is_string;
+use function method_exists;
+use function MongoDB\apply_type_map_to_document;
+use function MongoDB\BSON\fromPHP;
+use function MongoDB\BSON\toJSON;
+use function property_exists;
+use function sprintf;
+use function stream_context_create;
+use function stream_copy_to_stream;
+use function stream_get_meta_data;
+use function stream_get_wrappers;
+use function urlencode;
 
 /**
  * Bucket provides a public API for interacting with the GridFS files and chunks
@@ -38,24 +62,50 @@ use stdClass;
  */
 class Bucket
 {
+    /** @var string */
     private static $defaultBucketName = 'fs';
+
+    /** @var integer */
     private static $defaultChunkSizeBytes = 261120;
+
+    /** @var array */
     private static $defaultTypeMap = [
-        'array' => 'MongoDB\Model\BSONArray',
-        'document' => 'MongoDB\Model\BSONDocument',
-        'root' => 'MongoDB\Model\BSONDocument',
+        'array' => BSONArray::class,
+        'document' => BSONDocument::class,
+        'root' => BSONDocument::class,
     ];
+
+    /** @var string */
     private static $streamWrapperProtocol = 'gridfs';
 
+    /** @var CollectionWrapper */
     private $collectionWrapper;
+
+    /** @var string */
     private $databaseName;
+
+    /** @var Manager */
     private $manager;
+
+    /** @var string */
     private $bucketName;
+
+    /** @var boolean */
     private $disableMD5;
+
+    /** @var integer */
     private $chunkSizeBytes;
+
+    /** @var ReadConcern */
     private $readConcern;
+
+    /** @var ReadPreference */
     private $readPreference;
+
+    /** @var array */
     private $typeMap;
+
+    /** @var WriteConcern */
     private $writeConcern;
 
     /**
@@ -110,11 +160,11 @@ class Bucket
         }
 
         if (isset($options['readConcern']) && ! $options['readConcern'] instanceof ReadConcern) {
-            throw InvalidArgumentException::invalidType('"readConcern" option', $options['readConcern'], 'MongoDB\Driver\ReadConcern');
+            throw InvalidArgumentException::invalidType('"readConcern" option', $options['readConcern'], ReadConcern::class);
         }
 
         if (isset($options['readPreference']) && ! $options['readPreference'] instanceof ReadPreference) {
-            throw InvalidArgumentException::invalidType('"readPreference" option', $options['readPreference'], 'MongoDB\Driver\ReadPreference');
+            throw InvalidArgumentException::invalidType('"readPreference" option', $options['readPreference'], ReadPreference::class);
         }
 
         if (isset($options['typeMap']) && ! is_array($options['typeMap'])) {
@@ -122,7 +172,7 @@ class Bucket
         }
 
         if (isset($options['writeConcern']) && ! $options['writeConcern'] instanceof WriteConcern) {
-            throw InvalidArgumentException::invalidType('"writeConcern" option', $options['writeConcern'], 'MongoDB\Driver\WriteConcern');
+            throw InvalidArgumentException::invalidType('"writeConcern" option', $options['writeConcern'], WriteConcern::class);
         }
 
         $this->manager = $manager;
@@ -192,7 +242,7 @@ class Bucket
      */
     public function downloadToStream($id, $destination)
     {
-        if ( ! is_resource($destination) || get_resource_type($destination) != "stream") {
+        if (! is_resource($destination) || get_resource_type($destination) != "stream") {
             throw InvalidArgumentException::invalidType('$destination', $destination, 'resource');
         }
 
@@ -227,7 +277,7 @@ class Bucket
      */
     public function downloadToStreamByName($filename, $destination, array $options = [])
     {
-        if ( ! is_resource($destination) || get_resource_type($destination) != "stream") {
+        if (! is_resource($destination) || get_resource_type($destination) != "stream") {
             throw InvalidArgumentException::invalidType('$destination', $destination, 'resource');
         }
 
@@ -332,7 +382,7 @@ class Bucket
         $file = $this->getRawFileDocumentForStream($stream);
 
         // Filter the raw document through the specified type map
-        return \MongoDB\apply_type_map_to_document($file, $this->typeMap);
+        return apply_type_map_to_document($file, $this->typeMap);
     }
 
     /**
@@ -352,9 +402,9 @@ class Bucket
          * the root type so we can reliably access the ID.
          */
         $typeMap = ['root' => 'stdClass'] + $this->typeMap;
-        $file = \MongoDB\apply_type_map_to_document($file, $typeMap);
+        $file = apply_type_map_to_document($file, $typeMap);
 
-        if ( ! isset($file->_id) && ! property_exists($file, '_id')) {
+        if (! isset($file->_id) && ! property_exists($file, '_id')) {
             throw new CorruptFileException('file._id does not exist');
         }
 
@@ -531,7 +581,7 @@ class Bucket
             ? $updateResult->getMatchedCount() === 1
             : $this->collectionWrapper->findFileById($id) !== null;
 
-        if ( ! $found) {
+        if (! $found) {
             throw FileNotFoundException::byId($id, $this->getFilesNamespace());
         }
     }
@@ -561,7 +611,7 @@ class Bucket
      */
     public function uploadFromStream($filename, $source, array $options = [])
     {
-        if ( ! is_resource($source) || get_resource_type($source) != "stream") {
+        if (! is_resource($source) || get_resource_type($source) != "stream") {
             throw InvalidArgumentException::invalidType('$source', $source, 'resource');
         }
 
@@ -579,10 +629,10 @@ class Bucket
      */
     private function createPathForFile(stdClass $file)
     {
-        if ( ! is_object($file->_id) || method_exists($file->_id, '__toString')) {
+        if (! is_object($file->_id) || method_exists($file->_id, '__toString')) {
             $id = (string) $file->_id;
         } else {
-            $id = \MongoDB\BSON\toJSON(\MongoDB\BSON\fromPHP(['_id' => $file->_id]));
+            $id = toJSON(fromPHP(['_id' => $file->_id]));
         }
 
         return sprintf(
@@ -631,14 +681,14 @@ class Bucket
      */
     private function getRawFileDocumentForStream($stream)
     {
-        if ( ! is_resource($stream) || get_resource_type($stream) != "stream") {
+        if (! is_resource($stream) || get_resource_type($stream) != "stream") {
             throw InvalidArgumentException::invalidType('$stream', $stream, 'resource');
         }
 
         $metadata = stream_get_meta_data($stream);
 
-        if ( ! isset ($metadata['wrapper_data']) || ! $metadata['wrapper_data'] instanceof StreamWrapper) {
-            throw InvalidArgumentException::invalidType('$stream wrapper data', isset($metadata['wrapper_data']) ? $metadata['wrapper_data'] : null, 'MongoDB\Driver\GridFS\StreamWrapper');
+        if (! isset($metadata['wrapper_data']) || ! $metadata['wrapper_data'] instanceof StreamWrapper) {
+            throw InvalidArgumentException::invalidType('$stream wrapper data', isset($metadata['wrapper_data']) ? $metadata['wrapper_data'] : null, StreamWrapper::class);
         }
 
         return $metadata['wrapper_data']->getFile();
diff --git a/cache/stores/mongodb/MongoDB/GridFS/CollectionWrapper.php b/cache/stores/mongodb/MongoDB/GridFS/CollectionWrapper.php
index 754fd4b3cb0..dd4c1533614 100644
--- a/cache/stores/mongodb/MongoDB/GridFS/CollectionWrapper.php
+++ b/cache/stores/mongodb/MongoDB/GridFS/CollectionWrapper.php
@@ -18,11 +18,14 @@
 namespace MongoDB\GridFS;
 
 use MongoDB\Collection;
-use MongoDB\UpdateResult;
 use MongoDB\Driver\Cursor;
 use MongoDB\Driver\Manager;
 use MongoDB\Driver\ReadPreference;
+use MongoDB\Exception\InvalidArgumentException;
+use MongoDB\UpdateResult;
 use stdClass;
+use function abs;
+use function sprintf;
 
 /**
  * CollectionWrapper abstracts the GridFS files and chunks collections.
@@ -31,10 +34,19 @@ use stdClass;
  */
 class CollectionWrapper
 {
+    /** @var string */
     private $bucketName;
+
+    /** @var Collection */
     private $chunksCollection;
+
+    /** @var string */
     private $databaseName;
+
+    /** @var boolean */
     private $checkedIndexes = false;
+
+    /** @var Collection */
     private $filesCollection;
 
     /**
@@ -121,7 +133,7 @@ class CollectionWrapper
      *
      * @see Bucket::downloadToStreamByName()
      * @see Bucket::openDownloadStreamByName()
-     * @param string $filename
+     * @param string  $filename
      * @param integer $revision
      * @return stdClass|null
      */
@@ -234,7 +246,7 @@ class CollectionWrapper
      */
     public function insertChunk($chunk)
     {
-        if ( ! $this->checkedIndexes) {
+        if (! $this->checkedIndexes) {
             $this->ensureIndexes();
         }
 
@@ -250,7 +262,7 @@ class CollectionWrapper
      */
     public function insertFile($file)
     {
-        if ( ! $this->checkedIndexes) {
+        if (! $this->checkedIndexes) {
             $this->ensureIndexes();
         }
 
@@ -261,7 +273,7 @@ class CollectionWrapper
      * Updates the filename field in the file document for a given ID.
      *
      * @param mixed  $id
-     * @param string $filename 
+     * @param string $filename
      * @return UpdateResult
      */
     public function updateFilenameForId($id, $filename)
@@ -314,7 +326,7 @@ class CollectionWrapper
 
         $this->checkedIndexes = true;
 
-        if ( ! $this->isFilesCollectionEmpty()) {
+        if (! $this->isFilesCollectionEmpty()) {
             return;
         }
 
diff --git a/cache/stores/mongodb/MongoDB/GridFS/Exception/CorruptFileException.php b/cache/stores/mongodb/MongoDB/GridFS/Exception/CorruptFileException.php
index 787c9b886fb..c353725692e 100644
--- a/cache/stores/mongodb/MongoDB/GridFS/Exception/CorruptFileException.php
+++ b/cache/stores/mongodb/MongoDB/GridFS/Exception/CorruptFileException.php
@@ -18,6 +18,7 @@
 namespace MongoDB\GridFS\Exception;
 
 use MongoDB\Exception\RuntimeException;
+use function sprintf;
 
 class CorruptFileException extends RuntimeException
 {
diff --git a/cache/stores/mongodb/MongoDB/GridFS/Exception/FileNotFoundException.php b/cache/stores/mongodb/MongoDB/GridFS/Exception/FileNotFoundException.php
index 2d3d0376184..f0d222381c2 100644
--- a/cache/stores/mongodb/MongoDB/GridFS/Exception/FileNotFoundException.php
+++ b/cache/stores/mongodb/MongoDB/GridFS/Exception/FileNotFoundException.php
@@ -18,6 +18,9 @@
 namespace MongoDB\GridFS\Exception;
 
 use MongoDB\Exception\RuntimeException;
+use function MongoDB\BSON\fromPHP;
+use function MongoDB\BSON\toJSON;
+use function sprintf;
 
 class FileNotFoundException extends RuntimeException
 {
@@ -43,7 +46,7 @@ class FileNotFoundException extends RuntimeException
      */
     public static function byId($id, $namespace)
     {
-        $json = \MongoDB\BSON\toJSON(\MongoDB\BSON\fromPHP(['_id' => $id]));
+        $json = toJSON(fromPHP(['_id' => $id]));
 
         return new static(sprintf('File "%s" not found in "%s"', $json, $namespace));
     }
diff --git a/cache/stores/mongodb/MongoDB/GridFS/ReadableStream.php b/cache/stores/mongodb/MongoDB/GridFS/ReadableStream.php
index d49b21304e5..7978de97270 100644
--- a/cache/stores/mongodb/MongoDB/GridFS/ReadableStream.php
+++ b/cache/stores/mongodb/MongoDB/GridFS/ReadableStream.php
@@ -17,10 +17,17 @@
 
 namespace MongoDB\GridFS;
 
+use IteratorIterator;
 use MongoDB\Exception\InvalidArgumentException;
 use MongoDB\GridFS\Exception\CorruptFileException;
-use IteratorIterator;
 use stdClass;
+use function ceil;
+use function floor;
+use function is_integer;
+use function property_exists;
+use function sprintf;
+use function strlen;
+use function substr;
 
 /**
  * ReadableStream abstracts the process of reading a GridFS file.
@@ -29,15 +36,34 @@ use stdClass;
  */
 class ReadableStream
 {
+    /** @var string|null */
     private $buffer;
+
+    /** @var integer */
     private $bufferOffset = 0;
+
+    /** @var integer */
     private $chunkSize;
+
+    /** @var integer */
     private $chunkOffset = 0;
+
+    /** @var IteratorIterator|null */
     private $chunksIterator;
+
+    /** @var CollectionWrapper */
     private $collectionWrapper;
+
+    /** @var float|integer */
     private $expectedLastChunkSize = 0;
+
+    /** @var stdClass */
     private $file;
+
+    /** @var integer */
     private $length;
+
+    /** @var integer */
     private $numChunks = 0;
 
     /**
@@ -49,15 +75,15 @@ class ReadableStream
      */
     public function __construct(CollectionWrapper $collectionWrapper, stdClass $file)
     {
-        if ( ! isset($file->chunkSize) || ! is_integer($file->chunkSize) || $file->chunkSize < 1) {
+        if (! isset($file->chunkSize) || ! is_integer($file->chunkSize) || $file->chunkSize < 1) {
             throw new CorruptFileException('file.chunkSize is not an integer >= 1');
         }
 
-        if ( ! isset($file->length) || ! is_integer($file->length) || $file->length < 0) {
+        if (! isset($file->length) || ! is_integer($file->length) || $file->length < 0) {
             throw new CorruptFileException('file.length is not an integer > 0');
         }
 
-        if ( ! isset($file->_id) && ! property_exists($file, '_id')) {
+        if (! isset($file->_id) && ! property_exists($file, '_id')) {
             throw new CorruptFileException('file._id does not exist');
         }
 
@@ -202,6 +228,7 @@ class ReadableStream
          */
         if ($lastChunkOffset > $this->chunkOffset) {
             $this->chunksIterator = null;
+
             return;
         }
 
@@ -239,7 +266,7 @@ class ReadableStream
             return false;
         }
 
-        if ( ! $this->chunksIterator->valid()) {
+        if (! $this->chunksIterator->valid()) {
             throw CorruptFileException::missingChunk($this->chunkOffset);
         }
 
@@ -253,7 +280,7 @@ class ReadableStream
 
         $actualChunkSize = strlen($this->buffer);
 
-        $expectedChunkSize = ($this->chunkOffset === $this->numChunks - 1)
+        $expectedChunkSize = $this->chunkOffset === $this->numChunks - 1
             ? $this->expectedLastChunkSize
             : $this->chunkSize;
 
diff --git a/cache/stores/mongodb/MongoDB/GridFS/StreamWrapper.php b/cache/stores/mongodb/MongoDB/GridFS/StreamWrapper.php
index 29a2be68a0f..a79d4d904ec 100644
--- a/cache/stores/mongodb/MongoDB/GridFS/StreamWrapper.php
+++ b/cache/stores/mongodb/MongoDB/GridFS/StreamWrapper.php
@@ -17,9 +17,24 @@
 
 namespace MongoDB\GridFS;
 
-use MongoDB\BSON\UTCDateTime;
 use Exception;
+use MongoDB\BSON\UTCDateTime;
 use stdClass;
+use function explode;
+use function get_class;
+use function in_array;
+use function is_integer;
+use function sprintf;
+use function stream_context_get_options;
+use function stream_get_wrappers;
+use function stream_wrapper_register;
+use function stream_wrapper_unregister;
+use function trigger_error;
+use const E_USER_WARNING;
+use const SEEK_CUR;
+use const SEEK_END;
+use const SEEK_SET;
+use const STREAM_IS_URL;
 
 /**
  * Stream wrapper for reading and writing a GridFS file.
@@ -30,13 +45,16 @@ use stdClass;
  */
 class StreamWrapper
 {
-    /**
-     * @var resource|null Stream context (set by PHP)
-     */
+    /** @var resource|null Stream context (set by PHP) */
     public $context;
 
+    /** @var string|null */
     private $mode;
+
+    /** @var string|null */
     private $protocol;
+
+    /** @var ReadableStream|WritableStream|null */
     private $stream;
 
     /**
@@ -60,7 +78,7 @@ class StreamWrapper
             stream_wrapper_unregister($protocol);
         }
 
-        stream_wrapper_register($protocol, get_called_class(), \STREAM_IS_URL);
+        stream_wrapper_register($protocol, static::class, STREAM_IS_URL);
     }
 
     /**
@@ -81,7 +99,7 @@ class StreamWrapper
      */
     public function stream_eof()
     {
-        if ( ! $this->stream instanceof ReadableStream) {
+        if (! $this->stream instanceof ReadableStream) {
             return false;
         }
 
@@ -96,6 +114,7 @@ class StreamWrapper
      * @param string  $mode       Mode used to open the file (only "r" and "w" are supported)
      * @param integer $options    Additional flags set by the streams API
      * @param string  $openedPath Not used
+     * @return boolean
      */
     public function stream_open($path, $mode, $options, &$openedPath)
     {
@@ -125,14 +144,15 @@ class StreamWrapper
      */
     public function stream_read($length)
     {
-        if ( ! $this->stream instanceof ReadableStream) {
+        if (! $this->stream instanceof ReadableStream) {
             return '';
         }
 
         try {
             return $this->stream->readBytes($length);
         } catch (Exception $e) {
-            trigger_error(sprintf('%s: %s', get_class($e), $e->getMessage()), \E_USER_WARNING);
+            trigger_error(sprintf('%s: %s', get_class($e), $e->getMessage()), E_USER_WARNING);
+
             return false;
         }
     }
@@ -145,15 +165,15 @@ class StreamWrapper
      * @param integer $whence One of SEEK_SET, SEEK_CUR, or SEEK_END
      * @return boolean True if the position was updated and false otherwise
      */
-    public function stream_seek($offset, $whence = \SEEK_SET)
+    public function stream_seek($offset, $whence = SEEK_SET)
     {
         $size = $this->stream->getSize();
 
-        if ($whence === \SEEK_CUR) {
+        if ($whence === SEEK_CUR) {
             $offset += $this->stream->tell();
         }
 
-        if ($whence === \SEEK_END) {
+        if ($whence === SEEK_END) {
             $offset += $size;
         }
 
@@ -221,14 +241,15 @@ class StreamWrapper
      */
     public function stream_write($data)
     {
-        if ( ! $this->stream instanceof WritableStream) {
+        if (! $this->stream instanceof WritableStream) {
             return 0;
         }
 
         try {
             return $this->stream->writeBytes($data);
         } catch (Exception $e) {
-            trigger_error(sprintf('%s: %s', get_class($e), $e->getMessage()), \E_USER_WARNING);
+            trigger_error(sprintf('%s: %s', get_class($e), $e->getMessage()), E_USER_WARNING);
+
             return false;
         }
     }
@@ -241,6 +262,7 @@ class StreamWrapper
     private function getStatTemplate()
     {
         return [
+            // phpcs:disable Squiz.Arrays.ArrayDeclaration.IndexNoNewline
             0  => 0,  'dev'     => 0,
             1  => 0,  'ino'     => 0,
             2  => 0,  'mode'    => 0,
@@ -254,6 +276,7 @@ class StreamWrapper
             10 => 0,  'ctime'   => 0,
             11 => -1, 'blksize' => -1,
             12 => -1, 'blocks'  => -1,
+            // phpcs:enable
         ];
     }
 
diff --git a/cache/stores/mongodb/MongoDB/GridFS/WritableStream.php b/cache/stores/mongodb/MongoDB/GridFS/WritableStream.php
index 1fed3f9c86c..d7f1e4c47de 100644
--- a/cache/stores/mongodb/MongoDB/GridFS/WritableStream.php
+++ b/cache/stores/mongodb/MongoDB/GridFS/WritableStream.php
@@ -23,6 +23,19 @@ use MongoDB\BSON\UTCDateTime;
 use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
 use MongoDB\Exception\InvalidArgumentException;
 use stdClass;
+use function array_intersect_key;
+use function hash_final;
+use function hash_init;
+use function hash_update;
+use function is_array;
+use function is_bool;
+use function is_integer;
+use function is_object;
+use function is_string;
+use function MongoDB\is_string_array;
+use function sprintf;
+use function strlen;
+use function substr;
 
 /**
  * WritableStream abstracts the process of writing a GridFS file.
@@ -31,16 +44,34 @@ use stdClass;
  */
 class WritableStream
 {
+    /** @var integer */
     private static $defaultChunkSizeBytes = 261120;
 
+    /** @var string */
     private $buffer = '';
+
+    /** @var integer */
     private $chunkOffset = 0;
+
+    /** @var integer */
     private $chunkSize;
+
+    /** @var boolean */
     private $disableMD5;
+
+    /** @var CollectionWrapper */
     private $collectionWrapper;
+
+    /** @var array */
     private $file;
+
+    /** @var resource */
     private $hashCtx;
+
+    /** @var boolean */
     private $isClosed = false;
+
+    /** @var integer */
     private $length = 0;
 
     /**
@@ -74,12 +105,12 @@ class WritableStream
     public function __construct(CollectionWrapper $collectionWrapper, $filename, array $options = [])
     {
         $options += [
-            '_id' => new ObjectId,
+            '_id' => new ObjectId(),
             'chunkSizeBytes' => self::$defaultChunkSizeBytes,
             'disableMD5' => false,
         ];
 
-        if (isset($options['aliases']) && ! \MongoDB\is_string_array($options['aliases'])) {
+        if (isset($options['aliases']) && ! is_string_array($options['aliases'])) {
             throw InvalidArgumentException::invalidType('"aliases" option', $options['aliases'], 'array of strings');
         }
 
@@ -107,7 +138,7 @@ class WritableStream
         $this->collectionWrapper = $collectionWrapper;
         $this->disableMD5 = $options['disableMD5'];
 
-        if ( ! $this->disableMD5) {
+        if (! $this->disableMD5) {
             $this->hashCtx = hash_init('md5');
         }
 
@@ -233,9 +264,9 @@ class WritableStream
     private function fileCollectionInsert()
     {
         $this->file['length'] = $this->length;
-        $this->file['uploadDate'] = new UTCDateTime;
+        $this->file['uploadDate'] = new UTCDateTime();
 
-        if ( ! $this->disableMD5) {
+        if (! $this->disableMD5) {
             $this->file['md5'] = hash_final($this->hashCtx);
         }
 
@@ -265,7 +296,7 @@ class WritableStream
             'data' => new Binary($data, Binary::TYPE_GENERIC),
         ];
 
-        if ( ! $this->disableMD5) {
+        if (! $this->disableMD5) {
             hash_update($this->hashCtx, $data);
         }
 
diff --git a/cache/stores/mongodb/MongoDB/InsertManyResult.php b/cache/stores/mongodb/MongoDB/InsertManyResult.php
index a9ecb693990..2d288af4cfa 100644
--- a/cache/stores/mongodb/MongoDB/InsertManyResult.php
+++ b/cache/stores/mongodb/MongoDB/InsertManyResult.php
@@ -25,13 +25,16 @@ use MongoDB\Exception\BadMethodCallException;
  */
 class InsertManyResult
 {
+    /** @var WriteResult */
     private $writeResult;
+
+    /** @var mixed[] */
     private $insertedIds;
+
+    /** @var boolean */
     private $isAcknowledged;
 
     /**
-     * Constructor.
-     *
      * @param WriteResult $writeResult
      * @param mixed[]     $insertedIds
      */
diff --git a/cache/stores/mongodb/MongoDB/InsertOneResult.php b/cache/stores/mongodb/MongoDB/InsertOneResult.php
index 5a580bd3a17..c4dee6e9320 100644
--- a/cache/stores/mongodb/MongoDB/InsertOneResult.php
+++ b/cache/stores/mongodb/MongoDB/InsertOneResult.php
@@ -25,13 +25,16 @@ use MongoDB\Exception\BadMethodCallException;
  */
 class InsertOneResult
 {
+    /** @var WriteResult */
     private $writeResult;
+
+    /** @var mixed */
     private $insertedId;
+
+    /** @var boolean */
     private $isAcknowledged;
 
     /**
-     * Constructor.
-     *
      * @param WriteResult $writeResult
      * @param mixed       $insertedId
      */
diff --git a/cache/stores/mongodb/MongoDB/MapReduceResult.php b/cache/stores/mongodb/MongoDB/MapReduceResult.php
index 37ba38fde09..cda55a57a7f 100644
--- a/cache/stores/mongodb/MongoDB/MapReduceResult.php
+++ b/cache/stores/mongodb/MongoDB/MapReduceResult.php
@@ -20,6 +20,7 @@ namespace MongoDB;
 use IteratorAggregate;
 use stdClass;
 use Traversable;
+use function call_user_func;
 
 /**
  * Result class for mapReduce command results.
@@ -34,14 +35,19 @@ use Traversable;
  */
 class MapReduceResult implements IteratorAggregate
 {
+    /** @var callable */
     private $getIterator;
+
+    /** @var integer */
     private $executionTimeMS;
+
+    /** @var array */
     private $counts;
+
+    /** @var array */
     private $timing;
 
     /**
-     * Constructor.
-     *
      * @internal
      * @param callable $getIterator Callback that returns a Traversable for mapReduce results
      * @param stdClass $result      Result document from the mapReduce command
@@ -71,7 +77,7 @@ class MapReduceResult implements IteratorAggregate
      */
     public function getExecutionTimeMS()
     {
-        return $this->executionTimeMS;
+        return (integer) $this->executionTimeMS;
     }
 
     /**
diff --git a/cache/stores/mongodb/MongoDB/Model/BSONArray.php b/cache/stores/mongodb/MongoDB/Model/BSONArray.php
index 61dc9b4ccf1..8230a5e5a9d 100644
--- a/cache/stores/mongodb/MongoDB/Model/BSONArray.php
+++ b/cache/stores/mongodb/MongoDB/Model/BSONArray.php
@@ -17,10 +17,12 @@
 
 namespace MongoDB\Model;
 
-use MongoDB\BSON\Serializable;
-use MongoDB\BSON\Unserializable;
 use ArrayObject;
 use JsonSerializable;
+use MongoDB\BSON\Serializable;
+use MongoDB\BSON\Unserializable;
+use function array_values;
+use function MongoDB\recursive_copy;
 
 /**
  * Model class for a BSON array.
@@ -38,7 +40,7 @@ class BSONArray extends ArrayObject implements JsonSerializable, Serializable, U
     public function __clone()
     {
         foreach ($this as $key => $value) {
-            $this[$key] = \MongoDB\recursive_copy($value);
+            $this[$key] = recursive_copy($value);
         }
     }
 
@@ -52,7 +54,7 @@ class BSONArray extends ArrayObject implements JsonSerializable, Serializable, U
      */
     public static function __set_state(array $properties)
     {
-        $array = new static;
+        $array = new static();
         $array->exchangeArray($properties);
 
         return $array;
diff --git a/cache/stores/mongodb/MongoDB/Model/BSONDocument.php b/cache/stores/mongodb/MongoDB/Model/BSONDocument.php
index 90ea88705d4..b00ac48942f 100644
--- a/cache/stores/mongodb/MongoDB/Model/BSONDocument.php
+++ b/cache/stores/mongodb/MongoDB/Model/BSONDocument.php
@@ -17,10 +17,11 @@
 
 namespace MongoDB\Model;
 
-use MongoDB\BSON\Serializable;
-use MongoDB\BSON\Unserializable;
 use ArrayObject;
 use JsonSerializable;
+use MongoDB\BSON\Serializable;
+use MongoDB\BSON\Unserializable;
+use function MongoDB\recursive_copy;
 
 /**
  * Model class for a BSON document.
@@ -38,17 +39,18 @@ class BSONDocument extends ArrayObject implements JsonSerializable, Serializable
     public function __clone()
     {
         foreach ($this as $key => $value) {
-            $this[$key] = \MongoDB\recursive_copy($value);
+            $this[$key] = recursive_copy($value);
         }
     }
 
     /**
-     * Constructor.
-     *
      * This overrides the parent constructor to allow property access of entries
      * by default.
      *
      * @see http://php.net/arrayobject.construct
+     * @param array   $input
+     * @param integer $flags
+     * @param string  $iterator_class
      */
     public function __construct($input = [], $flags = ArrayObject::ARRAY_AS_PROPS, $iterator_class = 'ArrayIterator')
     {
@@ -65,7 +67,7 @@ class BSONDocument extends ArrayObject implements JsonSerializable, Serializable
      */
     public static function __set_state(array $properties)
     {
-        $document = new static;
+        $document = new static();
         $document->exchangeArray($properties);
 
         return $document;
diff --git a/cache/stores/mongodb/MongoDB/Model/BSONIterator.php b/cache/stores/mongodb/MongoDB/Model/BSONIterator.php
index f0827943dd2..093bfbe5566 100644
--- a/cache/stores/mongodb/MongoDB/Model/BSONIterator.php
+++ b/cache/stores/mongodb/MongoDB/Model/BSONIterator.php
@@ -17,22 +17,40 @@
 
 namespace MongoDB\Model;
 
-use MongoDB\Exception\UnexpectedValueException;
-use MongoDB\Model\BSONDocument;
 use Iterator;
+use MongoDB\Exception\InvalidArgumentException;
+use MongoDB\Exception\UnexpectedValueException;
+use function is_array;
+use function MongoDB\BSON\toPHP;
+use function sprintf;
+use function strlen;
+use function substr;
+use function unpack;
 
 /**
  * Iterator for BSON documents.
  */
 class BSONIterator implements Iterator
 {
+    /** @var integer */
     private static $bsonSize = 4;
 
+    /** @var string */
     private $buffer;
+
+    /** @var integer */
     private $bufferLength;
+
+    /** @var mixed */
     private $current;
+
+    /** @var integer */
     private $key = 0;
+
+    /** @var integer */
     private $position = 0;
+
+    /** @var array */
     private $options;
 
     /**
@@ -54,7 +72,7 @@ class BSONIterator implements Iterator
             throw InvalidArgumentException::invalidType('"typeMap" option', $options['typeMap'], 'array');
         }
 
-        if ( ! isset($options['typeMap'])) {
+        if (! isset($options['typeMap'])) {
             $options['typeMap'] = [];
         }
 
@@ -129,7 +147,7 @@ class BSONIterator implements Iterator
             throw new UnexpectedValueException(sprintf('Expected %d bytes; %d remaining', $documentLength, $this->bufferLength - $this->position));
         }
 
-        $this->current = \MongoDB\BSON\toPHP(substr($this->buffer, $this->position, $documentLength), $this->options['typeMap']);
+        $this->current = toPHP(substr($this->buffer, $this->position, $documentLength), $this->options['typeMap']);
         $this->position += $documentLength;
     }
 }
diff --git a/cache/stores/mongodb/MongoDB/Model/CachingIterator.php b/cache/stores/mongodb/MongoDB/Model/CachingIterator.php
index adad231cad5..ce56efa0da7 100644
--- a/cache/stores/mongodb/MongoDB/Model/CachingIterator.php
+++ b/cache/stores/mongodb/MongoDB/Model/CachingIterator.php
@@ -21,6 +21,11 @@ use Countable;
 use Generator;
 use Iterator;
 use Traversable;
+use function count;
+use function current;
+use function key;
+use function next;
+use function reset;
 
 /**
  * Iterator for wrapping a Traversable and caching its results.
@@ -33,14 +38,19 @@ use Traversable;
  */
 class CachingIterator implements Countable, Iterator
 {
+    /** @var array */
     private $items = [];
+
+    /** @var Generator */
     private $iterator;
+
+    /** @var boolean */
     private $iteratorAdvanced = false;
+
+    /** @var boolean */
     private $iteratorExhausted = false;
 
     /**
-     * Constructor.
-     *
      * Initialize the iterator and stores the first item in the cache. This
      * effectively rewinds the Traversable and the wrapping Generator, which
      * will execute up to its first yield statement. Additionally, this mimics
@@ -90,7 +100,7 @@ class CachingIterator implements Countable, Iterator
      */
     public function next()
     {
-        if ( ! $this->iteratorExhausted) {
+        if (! $this->iteratorExhausted) {
             $this->iterator->next();
             $this->storeCurrentItem();
         }
@@ -128,7 +138,7 @@ class CachingIterator implements Countable, Iterator
      */
     private function exhaustIterator()
     {
-        while ( ! $this->iteratorExhausted) {
+        while (! $this->iteratorExhausted) {
             $this->next();
         }
     }
diff --git a/cache/stores/mongodb/MongoDB/Model/ChangeStreamIterator.php b/cache/stores/mongodb/MongoDB/Model/ChangeStreamIterator.php
new file mode 100644
index 00000000000..cf60a369dc3
--- /dev/null
+++ b/cache/stores/mongodb/MongoDB/Model/ChangeStreamIterator.php
@@ -0,0 +1,292 @@
+<?php
+/*
+ * Copyright 2019 MongoDB, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+namespace MongoDB\Model;
+
+use IteratorIterator;
+use MongoDB\BSON\Serializable;
+use MongoDB\Driver\Cursor;
+use MongoDB\Driver\Monitoring\CommandFailedEvent;
+use MongoDB\Driver\Monitoring\CommandStartedEvent;
+use MongoDB\Driver\Monitoring\CommandSubscriber;
+use MongoDB\Driver\Monitoring\CommandSucceededEvent;
+use MongoDB\Exception\InvalidArgumentException;
+use MongoDB\Exception\ResumeTokenException;
+use MongoDB\Exception\UnexpectedValueException;
+use function count;
+use function is_array;
+use function is_integer;
+use function is_object;
+use function MongoDB\Driver\Monitoring\addSubscriber;
+use function MongoDB\Driver\Monitoring\removeSubscriber;
+
+/**
+ * ChangeStreamIterator wraps a change stream's tailable cursor.
+ *
+ * This iterator tracks the size of each batch in order to determine when the
+ * postBatchResumeToken is applicable. It also ensures that initial calls to
+ * rewind() do not execute getMore commands.
+ *
+ * @internal
+ */
+class ChangeStreamIterator extends IteratorIterator implements CommandSubscriber
+{
+    /** @var integer */
+    private $batchPosition = 0;
+
+    /** @var integer */
+    private $batchSize;
+
+    /** @var boolean */
+    private $isRewindNop;
+
+    /** @var boolean */
+    private $isValid = false;
+
+    /** @var object|null */
+    private $postBatchResumeToken;
+
+    /** @var array|object|null */
+    private $resumeToken;
+
+    /**
+     * @internal
+     * @param Cursor            $cursor
+     * @param integer           $firstBatchSize
+     * @param array|object|null $initialResumeToken
+     * @param object|null       $postBatchResumeToken
+     */
+    public function __construct(Cursor $cursor, $firstBatchSize, $initialResumeToken, $postBatchResumeToken)
+    {
+        if (! is_integer($firstBatchSize)) {
+            throw InvalidArgumentException::invalidType('$firstBatchSize', $firstBatchSize, 'integer');
+        }
+
+        if (isset($initialResumeToken) && ! is_array($initialResumeToken) && ! is_object($initialResumeToken)) {
+            throw InvalidArgumentException::invalidType('$initialResumeToken', $initialResumeToken, 'array or object');
+        }
+
+        if (isset($postBatchResumeToken) && ! is_object($postBatchResumeToken)) {
+            throw InvalidArgumentException::invalidType('$postBatchResumeToken', $postBatchResumeToken, 'object');
+        }
+
+        parent::__construct($cursor);
+
+        $this->batchSize = $firstBatchSize;
+        $this->isRewindNop = ($firstBatchSize === 0);
+        $this->postBatchResumeToken = $postBatchResumeToken;
+        $this->resumeToken = $initialResumeToken;
+    }
+
+    /** @internal */
+    final public function commandFailed(CommandFailedEvent $event)
+    {
+    }
+
+    /** @internal */
+    final public function commandStarted(CommandStartedEvent $event)
+    {
+        if ($event->getCommandName() !== 'getMore') {
+            return;
+        }
+
+        $this->batchPosition = 0;
+        $this->batchSize = null;
+        $this->postBatchResumeToken = null;
+    }
+
+    /** @internal */
+    final public function commandSucceeded(CommandSucceededEvent $event)
+    {
+        if ($event->getCommandName() !== 'getMore') {
+            return;
+        }
+
+        $reply = $event->getReply();
+
+        if (! isset($reply->cursor->nextBatch) || ! is_array($reply->cursor->nextBatch)) {
+            throw new UnexpectedValueException('getMore command did not return a "cursor.nextBatch" array');
+        }
+
+        $this->batchSize = count($reply->cursor->nextBatch);
+
+        if (isset($reply->cursor->postBatchResumeToken) && is_object($reply->cursor->postBatchResumeToken)) {
+            $this->postBatchResumeToken = $reply->cursor->postBatchResumeToken;
+        }
+    }
+
+    /**
+     * @see https://php.net/iteratoriterator.current
+     * @return mixed
+     */
+    public function current()
+    {
+        return $this->isValid ? parent::current() : null;
+    }
+
+    /**
+     * Returns the resume token for the iterator's current position.
+     *
+     * Null may be returned if no change documents have been iterated and the
+     * server did not include a postBatchResumeToken in its aggregate or getMore
+     * command response.
+     *
+     * @return array|object|null
+     */
+    public function getResumeToken()
+    {
+        return $this->resumeToken;
+    }
+
+    /**
+     * @see https://php.net/iteratoriterator.key
+     * @return mixed
+     */
+    public function key()
+    {
+        return $this->isValid ? parent::key() : null;
+    }
+
+    /**
+     * @see https://php.net/iteratoriterator.rewind
+     * @return void
+     */
+    public function next()
+    {
+        /* Determine if advancing the iterator will execute a getMore command
+         * (i.e. we are already positioned at the end of the current batch). If
+         * so, rely on the APM callbacks to reset $batchPosition and update
+         * $batchSize. Otherwise, we can forgo APM and manually increment
+         * $batchPosition after calling next(). */
+        $getMore = $this->isAtEndOfBatch();
+
+        if ($getMore) {
+            addSubscriber($this);
+        }
+
+        try {
+            parent::next();
+            $this->onIteration(! $getMore);
+        } finally {
+            if ($getMore) {
+                removeSubscriber($this);
+            }
+        }
+    }
+
+    /**
+     * @see https://php.net/iteratoriterator.rewind
+     * @return void
+     */
+    public function rewind()
+    {
+        if ($this->isRewindNop) {
+            return;
+        }
+
+        parent::rewind();
+        $this->onIteration(false);
+    }
+
+    /**
+     * @see https://php.net/iteratoriterator.valid
+     * @return boolean
+     */
+    public function valid()
+    {
+        return $this->isValid;
+    }
+
+    /**
+     * Extracts the resume token (i.e. "_id" field) from a change document.
+     *
+     * @param array|object $document Change document
+     * @return array|object
+     * @throws InvalidArgumentException
+     * @throws ResumeTokenException if the resume token is not found or invalid
+     */
+    private function extractResumeToken($document)
+    {
+        if (! is_array($document) && ! is_object($document)) {
+            throw InvalidArgumentException::invalidType('$document', $document, 'array or object');
+        }
+
+        if ($document instanceof Serializable) {
+            return $this->extractResumeToken($document->bsonSerialize());
+        }
+
+        $resumeToken = is_array($document)
+            ? (isset($document['_id']) ? $document['_id'] : null)
+            : (isset($document->_id) ? $document->_id : null);
+
+        if (! isset($resumeToken)) {
+            $this->isValid = false;
+            throw ResumeTokenException::notFound();
+        }
+
+        if (! is_array($resumeToken) && ! is_object($resumeToken)) {
+            $this->isValid = false;
+            throw ResumeTokenException::invalidType($resumeToken);
+        }
+
+        return $resumeToken;
+    }
+
+    /**
+     * Return whether the iterator is positioned at the end of the batch.
+     *
+     * @return boolean
+     */
+    private function isAtEndOfBatch()
+    {
+        return $this->batchPosition + 1 >= $this->batchSize;
+    }
+
+    /**
+     * Perform housekeeping after an iteration event.
+     *
+     * @see https://github.com/mongodb/specifications/blob/master/source/change-streams/change-streams.rst#updating-the-cached-resume-token
+     * @param boolean $incrementBatchPosition
+     */
+    private function onIteration($incrementBatchPosition)
+    {
+        $this->isValid = parent::valid();
+
+        /* Disable rewind()'s NOP behavior once we advance to a valid position.
+         * This will allow the driver to throw a LogicException if rewind() is
+         * called after the cursor has advanced past its first element. */
+        if ($this->isRewindNop && $this->isValid) {
+            $this->isRewindNop = false;
+        }
+
+        if ($incrementBatchPosition && $this->isValid) {
+            $this->batchPosition++;
+        }
+
+        /* If the iterator is positioned at the end of the batch, apply the
+         * postBatchResumeToken if it's available. This handles both the case
+         * where the current batch is empty (since onIteration() will be called
+         * after a successful getMore) and when the iterator has advanced to the
+         * last document in its current batch. Otherwise, extract a resume token
+         * from the current document if possible. */
+        if ($this->isAtEndOfBatch() && $this->postBatchResumeToken !== null) {
+            $this->resumeToken = $this->postBatchResumeToken;
+        } elseif ($this->isValid) {
+            $this->resumeToken = $this->extractResumeToken($this->current());
+        }
+    }
+}
diff --git a/cache/stores/mongodb/MongoDB/Model/CollectionInfo.php b/cache/stores/mongodb/MongoDB/Model/CollectionInfo.php
index 39b20c4a3b1..f4d61df2b71 100644
--- a/cache/stores/mongodb/MongoDB/Model/CollectionInfo.php
+++ b/cache/stores/mongodb/MongoDB/Model/CollectionInfo.php
@@ -17,8 +17,9 @@
 
 namespace MongoDB\Model;
 
-use MongoDB\Exception\BadMethodCallException;
 use ArrayAccess;
+use MongoDB\Exception\BadMethodCallException;
+use function array_key_exists;
 
 /**
  * Collection information model class.
@@ -33,11 +34,10 @@ use ArrayAccess;
  */
 class CollectionInfo implements ArrayAccess
 {
+    /** @var array */
     private $info;
 
     /**
-     * Constructor.
-     *
      * @param array $info Collection info
      */
     public function __construct(array $info)
@@ -63,6 +63,7 @@ class CollectionInfo implements ArrayAccess
      */
     public function getCappedMax()
     {
+        /* The MongoDB server might return this number as an integer or float */
         return isset($this->info['options']['max']) ? (integer) $this->info['options']['max'] : null;
     }
 
@@ -73,6 +74,7 @@ class CollectionInfo implements ArrayAccess
      */
     public function getCappedSize()
     {
+        /* The MongoDB server might return this number as an integer or float */
         return isset($this->info['options']['size']) ? (integer) $this->info['options']['size'] : null;
     }
 
@@ -134,21 +136,24 @@ class CollectionInfo implements ArrayAccess
      * Not supported.
      *
      * @see http://php.net/arrayaccess.offsetset
+     * @param mixed $key
+     * @param mixed $value
      * @throws BadMethodCallException
      */
     public function offsetSet($key, $value)
     {
-        throw BadMethodCallException::classIsImmutable(__CLASS__);
+        throw BadMethodCallException::classIsImmutable(self::class);
     }
 
     /**
      * Not supported.
      *
      * @see http://php.net/arrayaccess.offsetunset
+     * @param mixed $key
      * @throws BadMethodCallException
      */
     public function offsetUnset($key)
     {
-        throw BadMethodCallException::classIsImmutable(__CLASS__);
+        throw BadMethodCallException::classIsImmutable(self::class);
     }
 }
diff --git a/cache/stores/mongodb/MongoDB/Model/DatabaseInfo.php b/cache/stores/mongodb/MongoDB/Model/DatabaseInfo.php
index e93c5ca0a58..9b656113d6d 100644
--- a/cache/stores/mongodb/MongoDB/Model/DatabaseInfo.php
+++ b/cache/stores/mongodb/MongoDB/Model/DatabaseInfo.php
@@ -17,8 +17,10 @@
 
 namespace MongoDB\Model;
 
-use MongoDB\Exception\BadMethodCallException;
 use ArrayAccess;
+use MongoDB\Exception\BadMethodCallException;
+use function array_key_exists;
+
 /**
  * Database information model class.
  *
@@ -31,11 +33,10 @@ use ArrayAccess;
  */
 class DatabaseInfo implements ArrayAccess
 {
+    /** @var array */
     private $info;
 
     /**
-     * Constructor.
-     *
      * @param array $info Database info
      */
     public function __construct(array $info)
@@ -71,6 +72,7 @@ class DatabaseInfo implements ArrayAccess
      */
     public function getSizeOnDisk()
     {
+        /* The MongoDB server might return this number as an integer or float */
         return (integer) $this->info['sizeOnDisk'];
     }
 
@@ -112,21 +114,24 @@ class DatabaseInfo implements ArrayAccess
      * Not supported.
      *
      * @see http://php.net/arrayaccess.offsetset
+     * @param mixed $key
+     * @param mixed $value
      * @throws BadMethodCallException
      */
     public function offsetSet($key, $value)
     {
-        throw BadMethodCallException::classIsImmutable(__CLASS__);
+        throw BadMethodCallException::classIsImmutable(self::class);
     }
 
     /**
      * Not supported.
      *
      * @see http://php.net/arrayaccess.offsetunset
+     * @param mixed $key
      * @throws BadMethodCallException
      */
     public function offsetUnset($key)
     {
-        throw BadMethodCallException::classIsImmutable(__CLASS__);
+        throw BadMethodCallException::classIsImmutable(self::class);
     }
 }
diff --git a/cache/stores/mongodb/MongoDB/Model/DatabaseInfoLegacyIterator.php b/cache/stores/mongodb/MongoDB/Model/DatabaseInfoLegacyIterator.php
index 04be47e3061..e50b54166ef 100644
--- a/cache/stores/mongodb/MongoDB/Model/DatabaseInfoLegacyIterator.php
+++ b/cache/stores/mongodb/MongoDB/Model/DatabaseInfoLegacyIterator.php
@@ -17,6 +17,11 @@
 
 namespace MongoDB\Model;
 
+use function current;
+use function key;
+use function next;
+use function reset;
+
 /**
  * DatabaseInfoIterator for inline listDatabases command results.
  *
@@ -29,11 +34,10 @@ namespace MongoDB\Model;
  */
 class DatabaseInfoLegacyIterator implements DatabaseInfoIterator
 {
+    /** @var array */
     private $databases;
 
     /**
-     * Constructor.
-     *
      * @param array $databases
      */
     public function __construct(array $databases)
diff --git a/cache/stores/mongodb/MongoDB/Model/IndexInfo.php b/cache/stores/mongodb/MongoDB/Model/IndexInfo.php
index 7491f34aa83..ee8a29357a1 100644
--- a/cache/stores/mongodb/MongoDB/Model/IndexInfo.php
+++ b/cache/stores/mongodb/MongoDB/Model/IndexInfo.php
@@ -17,8 +17,10 @@
 
 namespace MongoDB\Model;
 
-use MongoDB\Exception\BadMethodCallException;
 use ArrayAccess;
+use MongoDB\Exception\BadMethodCallException;
+use function array_key_exists;
+use function array_search;
 
 /**
  * Index information model class.
@@ -37,11 +39,10 @@ use ArrayAccess;
  */
 class IndexInfo implements ArrayAccess
 {
+    /** @var array */
     private $info;
 
     /**
-     * Constructor.
-     *
      * @param array $info Index info
      */
     public function __construct(array $info)
@@ -206,21 +207,24 @@ class IndexInfo implements ArrayAccess
      * Not supported.
      *
      * @see http://php.net/arrayaccess.offsetset
+     * @param mixed $key
+     * @param mixed $value
      * @throws BadMethodCallException
      */
     public function offsetSet($key, $value)
     {
-        throw BadMethodCallException::classIsImmutable(__CLASS__);
+        throw BadMethodCallException::classIsImmutable(self::class);
     }
 
     /**
      * Not supported.
      *
      * @see http://php.net/arrayaccess.offsetunset
+     * @param mixed $key
      * @throws BadMethodCallException
      */
     public function offsetUnset($key)
     {
-        throw BadMethodCallException::classIsImmutable(__CLASS__);
+        throw BadMethodCallException::classIsImmutable(self::class);
     }
 }
diff --git a/cache/stores/mongodb/MongoDB/Model/IndexInput.php b/cache/stores/mongodb/MongoDB/Model/IndexInput.php
index b306fa002ab..ca85ccab943 100644
--- a/cache/stores/mongodb/MongoDB/Model/IndexInput.php
+++ b/cache/stores/mongodb/MongoDB/Model/IndexInput.php
@@ -19,6 +19,13 @@ namespace MongoDB\Model;
 
 use MongoDB\BSON\Serializable;
 use MongoDB\Exception\InvalidArgumentException;
+use function is_array;
+use function is_float;
+use function is_int;
+use function is_object;
+use function is_string;
+use function MongoDB\generate_index_name;
+use function sprintf;
 
 /**
  * Index input model class.
@@ -32,43 +39,42 @@ use MongoDB\Exception\InvalidArgumentException;
  */
 class IndexInput implements Serializable
 {
+    /** @var array */
     private $index;
 
     /**
-     * Constructor.
-     *
      * @param array $index Index specification
      * @throws InvalidArgumentException
      */
     public function __construct(array $index)
     {
-        if ( ! isset($index['key'])) {
+        if (! isset($index['key'])) {
             throw new InvalidArgumentException('Required "key" document is missing from index specification');
         }
 
-        if ( ! is_array($index['key']) && ! is_object($index['key'])) {
+        if (! is_array($index['key']) && ! is_object($index['key'])) {
             throw InvalidArgumentException::invalidType('"key" option', $index['key'], 'array or object');
         }
 
         foreach ($index['key'] as $fieldName => $order) {
-            if ( ! is_int($order) && ! is_float($order) && ! is_string($order)) {
+            if (! is_int($order) && ! is_float($order) && ! is_string($order)) {
                 throw InvalidArgumentException::invalidType(sprintf('order value for "%s" field within "key" option', $fieldName), $order, 'numeric or string');
             }
         }
 
-        if ( ! isset($index['ns'])) {
+        if (! isset($index['ns'])) {
             throw new InvalidArgumentException('Required "ns" option is missing from index specification');
         }
 
-        if ( ! is_string($index['ns'])) {
+        if (! is_string($index['ns'])) {
             throw InvalidArgumentException::invalidType('"ns" option', $index['ns'], 'string');
         }
 
-        if ( ! isset($index['name'])) {
-            $index['name'] = \MongoDB\generate_index_name($index['key']);
+        if (! isset($index['name'])) {
+            $index['name'] = generate_index_name($index['key']);
         }
 
-        if ( ! is_string($index['name'])) {
+        if (! is_string($index['name'])) {
             throw InvalidArgumentException::invalidType('"name" option', $index['name'], 'string');
         }
 
@@ -78,7 +84,7 @@ class IndexInput implements Serializable
     /**
      * Return the index name.
      *
-     * @param string
+     * @return string
      */
     public function __toString()
     {
diff --git a/cache/stores/mongodb/MongoDB/Model/TypeMapArrayIterator.php b/cache/stores/mongodb/MongoDB/Model/TypeMapArrayIterator.php
deleted file mode 100644
index b30a0ec02ef..00000000000
--- a/cache/stores/mongodb/MongoDB/Model/TypeMapArrayIterator.php
+++ /dev/null
@@ -1,166 +0,0 @@
-<?php
-/*
- * Copyright 2016-2017 MongoDB, Inc.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *   http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-namespace MongoDB\Model;
-
-use ArrayIterator;
-use MongoDB\Exception\BadMethodCallException;
-
-/**
- * Iterator for applying a type map to documents in inline command results.
- *
- * @internal
- */
-class TypeMapArrayIterator extends ArrayIterator
-{
-    private $typeMap;
-
-    /**
-     * Constructor.
-     *
-     * @param array $documents
-     * @param array $typeMap
-     */
-    public function __construct(array $documents = [], array $typeMap)
-    {
-        parent::__construct($documents);
-
-        $this->typeMap = $typeMap;
-    }
-
-    /**
-     * Not supported.
-     *
-     * @see http://php.net/arrayiterator.append
-     * @throws BadMethodCallException
-     */
-    public function append($value)
-    {
-        throw BadMethodCallException::classIsImmutable(__CLASS__);
-    }
-
-    /**
-     * Not supported.
-     *
-     * @see http://php.net/arrayiterator.asort
-     * @throws BadMethodCallException
-     */
-    public function asort()
-    {
-        throw BadMethodCallException::classIsImmutable(__CLASS__);
-    }
-
-    /**
-     * Return the current element with the type map applied to it.
-     *
-     * @see http://php.net/arrayiterator.current
-     * @return array|object
-     */
-    public function current()
-    {
-        return \MongoDB\apply_type_map_to_document(parent::current(), $this->typeMap);
-    }
-
-    /**
-     * Not supported.
-     *
-     * @see http://php.net/arrayiterator.ksort
-     * @throws BadMethodCallException
-     */
-    public function ksort()
-    {
-        throw BadMethodCallException::classIsImmutable(__CLASS__);
-    }
-
-    /**
-     * Not supported.
-     *
-     * @see http://php.net/arrayiterator.natcasesort
-     * @throws BadMethodCallException
-     */
-    public function natcasesort()
-    {
-        throw BadMethodCallException::classIsImmutable(__CLASS__);
-    }
-
-    /**
-     * Not supported.
-     *
-     * @see http://php.net/arrayiterator.natsort
-     * @throws BadMethodCallException
-     */
-    public function natsort()
-    {
-        throw BadMethodCallException::classIsImmutable(__CLASS__);
-    }
-
-    /**
-     * Return the value from the provided offset with the type map applied.
-     *
-     * @see http://php.net/arrayiterator.offsetget
-     * @param mixed $offset
-     * @return array|object
-     */
-    public function offsetGet($offset)
-    {
-        return \MongoDB\apply_type_map_to_document(parent::offsetGet($offset), $this->typeMap);
-    }
-
-    /**
-     * Not supported.
-     *
-     * @see http://php.net/arrayiterator.offsetset
-     * @throws BadMethodCallException
-     */
-    public function offsetSet($index, $newval)
-    {
-        throw BadMethodCallException::classIsImmutable(__CLASS__);
-    }
-
-    /**
-     * Not supported.
-     *
-     * @see http://php.net/arrayiterator.offsetunset
-     * @throws BadMethodCallException
-     */
-    public function offsetUnset($index)
-    {
-        throw BadMethodCallException::classIsImmutable(__CLASS__);
-    }
-
-    /**
-     * Not supported.
-     *
-     * @see http://php.net/arrayiterator.uasort
-     * @throws BadMethodCallException
-     */
-    public function uasort($cmp_function)
-    {
-        throw BadMethodCallException::classIsImmutable(__CLASS__);
-    }
-
-    /**
-     * Not supported.
-     *
-     * @see http://php.net/arrayiterator.uksort
-     * @throws BadMethodCallException
-     */
-    public function uksort($cmp_function)
-    {
-        throw BadMethodCallException::classIsImmutable(__CLASS__);
-    }
-}
diff --git a/cache/stores/mongodb/MongoDB/Operation/Aggregate.php b/cache/stores/mongodb/MongoDB/Operation/Aggregate.php
index 2ddba685852..fc2e9ee40f9 100644
--- a/cache/stores/mongodb/MongoDB/Operation/Aggregate.php
+++ b/cache/stores/mongodb/MongoDB/Operation/Aggregate.php
@@ -17,20 +17,29 @@
 
 namespace MongoDB\Operation;
 
+use ArrayIterator;
 use MongoDB\Driver\Command;
+use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
 use MongoDB\Driver\ReadConcern;
 use MongoDB\Driver\ReadPreference;
 use MongoDB\Driver\Server;
 use MongoDB\Driver\Session;
 use MongoDB\Driver\WriteConcern;
-use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
 use MongoDB\Exception\InvalidArgumentException;
 use MongoDB\Exception\UnexpectedValueException;
 use MongoDB\Exception\UnsupportedException;
-use MongoDB\Model\TypeMapArrayIterator;
-use ArrayIterator;
 use stdClass;
 use Traversable;
+use function current;
+use function is_array;
+use function is_bool;
+use function is_integer;
+use function is_object;
+use function is_string;
+use function MongoDB\create_field_path_type_map;
+use function MongoDB\is_last_pipeline_operator_write;
+use function MongoDB\server_supports_feature;
+use function sprintf;
 
 /**
  * Operation for the aggregate command.
@@ -41,14 +50,28 @@ use Traversable;
  */
 class Aggregate implements Executable
 {
+    /** @var integer */
     private static $wireVersionForCollation = 5;
+
+    /** @var integer */
     private static $wireVersionForDocumentLevelValidation = 4;
+
+    /** @var integer */
     private static $wireVersionForReadConcern = 4;
+
+    /** @var integer */
     private static $wireVersionForWriteConcern = 5;
 
+    /** @var string */
     private $databaseName;
+
+    /** @var string|null */
     private $collectionName;
+
+    /** @var array */
     private $pipeline;
+
+    /** @var array */
     private $options;
 
     /**
@@ -63,8 +86,8 @@ class Aggregate implements Executable
      *  * batchSize (integer): The number of documents to return per batch.
      *
      *  * bypassDocumentValidation (boolean): If true, allows the write to
-     *    circumvent document level validation. This only applies when the $out
-     *    stage is specified.
+     *    circumvent document level validation. This only applies when an $out
+     *    or $merge stage is specified.
      *
      *    For servers < 3.2, this option is ignored as document level validation
      *    is not available.
@@ -87,15 +110,14 @@ class Aggregate implements Executable
      *  * maxTimeMS (integer): The maximum amount of time to allow the query to
      *    run.
      *
-     *  * readConcern (MongoDB\Driver\ReadConcern): Read concern. Note that a
-     *    "majority" read concern is not compatible with the $out stage.
+     *  * readConcern (MongoDB\Driver\ReadConcern): Read concern.
      *
      *    This is not supported for server versions < 3.2 and will result in an
      *    exception at execution time if used.
      *
      *  * readPreference (MongoDB\Driver\ReadPreference): Read preference.
      *
-     *    This option is ignored if the $out stage is specified.
+     *    This option is ignored if an $out or $merge stage is specified.
      *
      *  * session (MongoDB\Driver\Session): Client session.
      *
@@ -111,7 +133,7 @@ class Aggregate implements Executable
      *    mongod/mongos upgrades.
      *
      *  * writeConcern (MongoDB\Driver\WriteConcern): Write concern. This only
-     *    applies when the $out stage is specified.
+     *    applies when an $out or $merge stage is specified.
      *
      *    This is not supported for server versions < 3.4 and will result in an
      *    exception at execution time if used.
@@ -134,7 +156,7 @@ class Aggregate implements Executable
                 throw new InvalidArgumentException(sprintf('$pipeline is not a list (unexpected index: "%s")', $i));
             }
 
-            if ( ! is_array($operation) && ! is_object($operation)) {
+            if (! is_array($operation) && ! is_object($operation)) {
                 throw InvalidArgumentException::invalidType(sprintf('$pipeline[%d]', $i), $operation, 'array or object');
             }
 
@@ -146,7 +168,7 @@ class Aggregate implements Executable
             'useCursor' => true,
         ];
 
-        if ( ! is_bool($options['allowDiskUse'])) {
+        if (! is_bool($options['allowDiskUse'])) {
             throw InvalidArgumentException::invalidType('"allowDiskUse" option', $options['allowDiskUse'], 'boolean');
         }
 
@@ -183,27 +205,27 @@ class Aggregate implements Executable
         }
 
         if (isset($options['readConcern']) && ! $options['readConcern'] instanceof ReadConcern) {
-            throw InvalidArgumentException::invalidType('"readConcern" option', $options['readConcern'], 'MongoDB\Driver\ReadConcern');
+            throw InvalidArgumentException::invalidType('"readConcern" option', $options['readConcern'], ReadConcern::class);
         }
 
         if (isset($options['readPreference']) && ! $options['readPreference'] instanceof ReadPreference) {
-            throw InvalidArgumentException::invalidType('"readPreference" option', $options['readPreference'], 'MongoDB\Driver\ReadPreference');
+            throw InvalidArgumentException::invalidType('"readPreference" option', $options['readPreference'], ReadPreference::class);
         }
 
         if (isset($options['session']) && ! $options['session'] instanceof Session) {
-            throw InvalidArgumentException::invalidType('"session" option', $options['session'], 'MongoDB\Driver\Session');
+            throw InvalidArgumentException::invalidType('"session" option', $options['session'], Session::class);
         }
 
         if (isset($options['typeMap']) && ! is_array($options['typeMap'])) {
             throw InvalidArgumentException::invalidType('"typeMap" option', $options['typeMap'], 'array');
         }
 
-        if ( ! is_bool($options['useCursor'])) {
+        if (! is_bool($options['useCursor'])) {
             throw InvalidArgumentException::invalidType('"useCursor" option', $options['useCursor'], 'boolean');
         }
 
         if (isset($options['writeConcern']) && ! $options['writeConcern'] instanceof WriteConcern) {
-            throw InvalidArgumentException::invalidType('"writeConcern" option', $options['writeConcern'], 'MongoDB\Driver\WriteConcern');
+            throw InvalidArgumentException::invalidType('"writeConcern" option', $options['writeConcern'], WriteConcern::class);
         }
 
         if (isset($options['batchSize']) && ! $options['useCursor']) {
@@ -218,7 +240,7 @@ class Aggregate implements Executable
             unset($options['writeConcern']);
         }
 
-        if ( ! empty($options['explain'])) {
+        if (! empty($options['explain'])) {
             $options['useCursor'] = false;
         }
 
@@ -240,25 +262,35 @@ class Aggregate implements Executable
      */
     public function execute(Server $server)
     {
-        if (isset($this->options['collation']) && ! \MongoDB\server_supports_feature($server, self::$wireVersionForCollation)) {
+        if (isset($this->options['collation']) && ! server_supports_feature($server, self::$wireVersionForCollation)) {
             throw UnsupportedException::collationNotSupported();
         }
 
-        if (isset($this->options['readConcern']) && ! \MongoDB\server_supports_feature($server, self::$wireVersionForReadConcern)) {
+        if (isset($this->options['readConcern']) && ! server_supports_feature($server, self::$wireVersionForReadConcern)) {
             throw UnsupportedException::readConcernNotSupported();
         }
 
-        if (isset($this->options['writeConcern']) && ! \MongoDB\server_supports_feature($server, self::$wireVersionForWriteConcern)) {
+        if (isset($this->options['writeConcern']) && ! server_supports_feature($server, self::$wireVersionForWriteConcern)) {
             throw UnsupportedException::writeConcernNotSupported();
         }
 
+        $inTransaction = isset($this->options['session']) && $this->options['session']->isInTransaction();
+        if ($inTransaction) {
+            if (isset($this->options['readConcern'])) {
+                throw UnsupportedException::readConcernNotSupportedInTransaction();
+            }
+            if (isset($this->options['writeConcern'])) {
+                throw UnsupportedException::writeConcernNotSupportedInTransaction();
+            }
+        }
+
         $hasExplain = ! empty($this->options['explain']);
-        $hasOutStage = \MongoDB\is_last_pipeline_operator_out($this->pipeline);
+        $hasWriteStage = is_last_pipeline_operator_write($this->pipeline);
 
-        $command = $this->createCommand($server);
-        $options = $this->createOptions($hasOutStage, $hasExplain);
+        $command = $this->createCommand($server, $hasWriteStage);
+        $options = $this->createOptions($hasWriteStage, $hasExplain);
 
-        $cursor = ($hasOutStage && ! $hasExplain)
+        $cursor = $hasWriteStage && ! $hasExplain
             ? $server->executeReadWriteCommand($this->databaseName, $command, $options)
             : $server->executeReadCommand($this->databaseName, $command, $options);
 
@@ -270,14 +302,14 @@ class Aggregate implements Executable
             return $cursor;
         }
 
-        $result = current($cursor->toArray());
-
-        if ( ! isset($result->result) || ! is_array($result->result)) {
-            throw new UnexpectedValueException('aggregate command did not return a "result" array');
+        if (isset($this->options['typeMap'])) {
+            $cursor->setTypeMap(create_field_path_type_map($this->options['typeMap'], 'result.$'));
         }
 
-        if (isset($this->options['typeMap'])) {
-            return new TypeMapArrayIterator($result->result, $this->options['typeMap']);
+        $result = current($cursor->toArray());
+
+        if (! isset($result->result) || ! is_array($result->result)) {
+            throw new UnexpectedValueException('aggregate command did not return a "result" array');
         }
 
         return new ArrayIterator($result->result);
@@ -287,9 +319,10 @@ class Aggregate implements Executable
      * Create the aggregate command.
      *
      * @param Server  $server
+     * @param boolean $hasWriteStage
      * @return Command
      */
-    private function createCommand(Server $server)
+    private function createCommand(Server $server, $hasWriteStage)
     {
         $cmd = [
             'aggregate' => isset($this->collectionName) ? $this->collectionName : 1,
@@ -299,7 +332,9 @@ class Aggregate implements Executable
 
         $cmd['allowDiskUse'] = $this->options['allowDiskUse'];
 
-        if (isset($this->options['bypassDocumentValidation']) && \MongoDB\server_supports_feature($server, self::$wireVersionForDocumentLevelValidation)) {
+        if (! empty($this->options['bypassDocumentValidation']) &&
+            server_supports_feature($server, self::$wireVersionForDocumentLevelValidation)
+        ) {
             $cmd['bypassDocumentValidation'] = $this->options['bypassDocumentValidation'];
         }
 
@@ -322,9 +357,12 @@ class Aggregate implements Executable
         }
 
         if ($this->options['useCursor']) {
-            $cmd['cursor'] = isset($this->options["batchSize"])
+            /* Ignore batchSize if pipeline includes an $out or $merge stage, as
+             * no documents will be returned and sending a batchSize of zero
+             * could prevent the pipeline from executing at all. */
+            $cmd['cursor'] = isset($this->options["batchSize"]) && ! $hasWriteStage
                 ? ['batchSize' => $this->options["batchSize"]]
-                : new stdClass;
+                : new stdClass();
         }
 
         return new Command($cmd, $cmdOptions);
@@ -335,10 +373,11 @@ class Aggregate implements Executable
      *
      * @see http://php.net/manual/en/mongodb-driver-server.executereadcommand.php
      * @see http://php.net/manual/en/mongodb-driver-server.executereadwritecommand.php
-     * @param boolean $hasOutStage
+     * @param boolean $hasWriteStage
+     * @param boolean $hasExplain
      * @return array
      */
-    private function createOptions($hasOutStage, $hasExplain)
+    private function createOptions($hasWriteStage, $hasExplain)
     {
         $options = [];
 
@@ -346,7 +385,7 @@ class Aggregate implements Executable
             $options['readConcern'] = $this->options['readConcern'];
         }
 
-        if ( ! $hasOutStage && isset($this->options['readPreference'])) {
+        if (! $hasWriteStage && isset($this->options['readPreference'])) {
             $options['readPreference'] = $this->options['readPreference'];
         }
 
@@ -354,7 +393,7 @@ class Aggregate implements Executable
             $options['session'] = $this->options['session'];
         }
 
-        if ($hasOutStage && ! $hasExplain && isset($this->options['writeConcern'])) {
+        if ($hasWriteStage && ! $hasExplain && isset($this->options['writeConcern'])) {
             $options['writeConcern'] = $this->options['writeConcern'];
         }
 
diff --git a/cache/stores/mongodb/MongoDB/Operation/BulkWrite.php b/cache/stores/mongodb/MongoDB/Operation/BulkWrite.php
index 82ef082ac43..95bd4bb1c43 100644
--- a/cache/stores/mongodb/MongoDB/Operation/BulkWrite.php
+++ b/cache/stores/mongodb/MongoDB/Operation/BulkWrite.php
@@ -19,12 +19,23 @@ namespace MongoDB\Operation;
 
 use MongoDB\BulkWriteResult;
 use MongoDB\Driver\BulkWrite as Bulk;
+use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
 use MongoDB\Driver\Server;
 use MongoDB\Driver\Session;
 use MongoDB\Driver\WriteConcern;
-use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
 use MongoDB\Exception\InvalidArgumentException;
 use MongoDB\Exception\UnsupportedException;
+use function array_key_exists;
+use function count;
+use function current;
+use function is_array;
+use function is_bool;
+use function is_object;
+use function key;
+use function MongoDB\is_first_key_operator;
+use function MongoDB\is_pipeline;
+use function MongoDB\server_supports_feature;
+use function sprintf;
 
 /**
  * Operation for executing multiple write operations.
@@ -41,15 +52,31 @@ class BulkWrite implements Executable
     const UPDATE_MANY = 'updateMany';
     const UPDATE_ONE  = 'updateOne';
 
+    /** @var integer */
     private static $wireVersionForArrayFilters = 6;
+
+    /** @var integer */
     private static $wireVersionForCollation = 5;
+
+    /** @var integer */
     private static $wireVersionForDocumentLevelValidation = 4;
 
+    /** @var string */
     private $databaseName;
+
+    /** @var string */
     private $collectionName;
+
+    /** @var array[] */
     private $operations;
+
+    /** @var array */
     private $options;
+
+    /** @var boolean */
     private $isArrayFiltersUsed = false;
+
+    /** @var boolean */
     private $isCollationUsed = false;
 
     /**
@@ -132,7 +159,7 @@ class BulkWrite implements Executable
                 throw new InvalidArgumentException(sprintf('$operations is not a list (unexpected index: "%s")', $i));
             }
 
-            if ( ! is_array($operation)) {
+            if (! is_array($operation)) {
                 throw InvalidArgumentException::invalidType(sprintf('$operations[%d]', $i), $operation, 'array');
             }
 
@@ -143,11 +170,11 @@ class BulkWrite implements Executable
             $type = key($operation);
             $args = current($operation);
 
-            if ( ! isset($args[0]) && ! array_key_exists(0, $args)) {
+            if (! isset($args[0]) && ! array_key_exists(0, $args)) {
                 throw new InvalidArgumentException(sprintf('Missing first argument for $operations[%d]["%s"]', $i, $type));
             }
 
-            if ( ! is_array($args[0]) && ! is_object($args[0])) {
+            if (! is_array($args[0]) && ! is_object($args[0])) {
                 throw InvalidArgumentException::invalidType(sprintf('$operations[%d]["%s"][0]', $i, $type), $args[0], 'array or object');
             }
 
@@ -157,11 +184,11 @@ class BulkWrite implements Executable
 
                 case self::DELETE_MANY:
                 case self::DELETE_ONE:
-                    if ( ! isset($args[1])) {
+                    if (! isset($args[1])) {
                         $args[1] = [];
                     }
 
-                    if ( ! is_array($args[1])) {
+                    if (! is_array($args[1])) {
                         throw InvalidArgumentException::invalidType(sprintf('$operations[%d]["%s"][1]', $i, $type), $args[1], 'array');
                     }
 
@@ -170,7 +197,7 @@ class BulkWrite implements Executable
                     if (isset($args[1]['collation'])) {
                         $this->isCollationUsed = true;
 
-                        if ( ! is_array($args[1]['collation']) && ! is_object($args[1]['collation'])) {
+                        if (! is_array($args[1]['collation']) && ! is_object($args[1]['collation'])) {
                             throw InvalidArgumentException::invalidType(sprintf('$operations[%d]["%s"][1]["collation"]', $i, $type), $args[1]['collation'], 'array or object');
                         }
                     }
@@ -180,23 +207,23 @@ class BulkWrite implements Executable
                     break;
 
                 case self::REPLACE_ONE:
-                    if ( ! isset($args[1]) && ! array_key_exists(1, $args)) {
+                    if (! isset($args[1]) && ! array_key_exists(1, $args)) {
                         throw new InvalidArgumentException(sprintf('Missing second argument for $operations[%d]["%s"]', $i, $type));
                     }
 
-                    if ( ! is_array($args[1]) && ! is_object($args[1])) {
+                    if (! is_array($args[1]) && ! is_object($args[1])) {
                         throw InvalidArgumentException::invalidType(sprintf('$operations[%d]["%s"][1]', $i, $type), $args[1], 'array or object');
                     }
 
-                    if (\MongoDB\is_first_key_operator($args[1])) {
+                    if (is_first_key_operator($args[1])) {
                         throw new InvalidArgumentException(sprintf('First key in $operations[%d]["%s"][1] is an update operator', $i, $type));
                     }
 
-                    if ( ! isset($args[2])) {
+                    if (! isset($args[2])) {
                         $args[2] = [];
                     }
 
-                    if ( ! is_array($args[2])) {
+                    if (! is_array($args[2])) {
                         throw InvalidArgumentException::invalidType(sprintf('$operations[%d]["%s"][2]', $i, $type), $args[2], 'array');
                     }
 
@@ -206,12 +233,12 @@ class BulkWrite implements Executable
                     if (isset($args[2]['collation'])) {
                         $this->isCollationUsed = true;
 
-                        if ( ! is_array($args[2]['collation']) && ! is_object($args[2]['collation'])) {
+                        if (! is_array($args[2]['collation']) && ! is_object($args[2]['collation'])) {
                             throw InvalidArgumentException::invalidType(sprintf('$operations[%d]["%s"][2]["collation"]', $i, $type), $args[2]['collation'], 'array or object');
                         }
                     }
 
-                    if ( ! is_bool($args[2]['upsert'])) {
+                    if (! is_bool($args[2]['upsert'])) {
                         throw InvalidArgumentException::invalidType(sprintf('$operations[%d]["%s"][2]["upsert"]', $i, $type), $args[2]['upsert'], 'boolean');
                     }
 
@@ -221,23 +248,23 @@ class BulkWrite implements Executable
 
                 case self::UPDATE_MANY:
                 case self::UPDATE_ONE:
-                    if ( ! isset($args[1]) && ! array_key_exists(1, $args)) {
+                    if (! isset($args[1]) && ! array_key_exists(1, $args)) {
                         throw new InvalidArgumentException(sprintf('Missing second argument for $operations[%d]["%s"]', $i, $type));
                     }
 
-                    if ( ! is_array($args[1]) && ! is_object($args[1])) {
+                    if (! is_array($args[1]) && ! is_object($args[1])) {
                         throw InvalidArgumentException::invalidType(sprintf('$operations[%d]["%s"][1]', $i, $type), $args[1], 'array or object');
                     }
 
-                    if ( ! \MongoDB\is_first_key_operator($args[1])) {
-                        throw new InvalidArgumentException(sprintf('First key in $operations[%d]["%s"][1] is not an update operator', $i, $type));
+                    if (! is_first_key_operator($args[1]) && ! is_pipeline($args[1])) {
+                        throw new InvalidArgumentException(sprintf('First key in $operations[%d]["%s"][1] is neither an update operator nor a pipeline', $i, $type));
                     }
 
-                    if ( ! isset($args[2])) {
+                    if (! isset($args[2])) {
                         $args[2] = [];
                     }
 
-                    if ( ! is_array($args[2])) {
+                    if (! is_array($args[2])) {
                         throw InvalidArgumentException::invalidType(sprintf('$operations[%d]["%s"][2]', $i, $type), $args[2], 'array');
                     }
 
@@ -247,7 +274,7 @@ class BulkWrite implements Executable
                     if (isset($args[2]['arrayFilters'])) {
                         $this->isArrayFiltersUsed = true;
 
-                        if ( ! is_array($args[2]['arrayFilters'])) {
+                        if (! is_array($args[2]['arrayFilters'])) {
                             throw InvalidArgumentException::invalidType(sprintf('$operations[%d]["%s"][2]["arrayFilters"]', $i, $type), $args[2]['arrayFilters'], 'array');
                         }
                     }
@@ -255,12 +282,12 @@ class BulkWrite implements Executable
                     if (isset($args[2]['collation'])) {
                         $this->isCollationUsed = true;
 
-                        if ( ! is_array($args[2]['collation']) && ! is_object($args[2]['collation'])) {
+                        if (! is_array($args[2]['collation']) && ! is_object($args[2]['collation'])) {
                             throw InvalidArgumentException::invalidType(sprintf('$operations[%d]["%s"][2]["collation"]', $i, $type), $args[2]['collation'], 'array or object');
                         }
                     }
 
-                    if ( ! is_bool($args[2]['upsert'])) {
+                    if (! is_bool($args[2]['upsert'])) {
                         throw InvalidArgumentException::invalidType(sprintf('$operations[%d]["%s"][2]["upsert"]', $i, $type), $args[2]['upsert'], 'boolean');
                     }
 
@@ -281,16 +308,16 @@ class BulkWrite implements Executable
             throw InvalidArgumentException::invalidType('"bypassDocumentValidation" option', $options['bypassDocumentValidation'], 'boolean');
         }
 
-        if ( ! is_bool($options['ordered'])) {
+        if (! is_bool($options['ordered'])) {
             throw InvalidArgumentException::invalidType('"ordered" option', $options['ordered'], 'boolean');
         }
 
         if (isset($options['session']) && ! $options['session'] instanceof Session) {
-            throw InvalidArgumentException::invalidType('"session" option', $options['session'], 'MongoDB\Driver\Session');
+            throw InvalidArgumentException::invalidType('"session" option', $options['session'], Session::class);
         }
 
         if (isset($options['writeConcern']) && ! $options['writeConcern'] instanceof WriteConcern) {
-            throw InvalidArgumentException::invalidType('"writeConcern" option', $options['writeConcern'], 'MongoDB\Driver\WriteConcern');
+            throw InvalidArgumentException::invalidType('"writeConcern" option', $options['writeConcern'], WriteConcern::class);
         }
 
         if (isset($options['writeConcern']) && $options['writeConcern']->isDefault()) {
@@ -314,17 +341,24 @@ class BulkWrite implements Executable
      */
     public function execute(Server $server)
     {
-        if ($this->isArrayFiltersUsed && ! \MongoDB\server_supports_feature($server, self::$wireVersionForArrayFilters)) {
+        if ($this->isArrayFiltersUsed && ! server_supports_feature($server, self::$wireVersionForArrayFilters)) {
             throw UnsupportedException::arrayFiltersNotSupported();
         }
 
-        if ($this->isCollationUsed && ! \MongoDB\server_supports_feature($server, self::$wireVersionForCollation)) {
+        if ($this->isCollationUsed && ! server_supports_feature($server, self::$wireVersionForCollation)) {
             throw UnsupportedException::collationNotSupported();
         }
 
+        $inTransaction = isset($this->options['session']) && $this->options['session']->isInTransaction();
+        if ($inTransaction && isset($this->options['writeConcern'])) {
+            throw UnsupportedException::writeConcernNotSupportedInTransaction();
+        }
+
         $options = ['ordered' => $this->options['ordered']];
 
-        if (isset($this->options['bypassDocumentValidation']) && \MongoDB\server_supports_feature($server, self::$wireVersionForDocumentLevelValidation)) {
+        if (! empty($this->options['bypassDocumentValidation']) &&
+            server_supports_feature($server, self::$wireVersionForDocumentLevelValidation)
+        ) {
             $options['bypassDocumentValidation'] = $this->options['bypassDocumentValidation'];
         }
 
diff --git a/cache/stores/mongodb/MongoDB/Operation/Count.php b/cache/stores/mongodb/MongoDB/Operation/Count.php
index 771e276248f..2e00ae555f3 100644
--- a/cache/stores/mongodb/MongoDB/Operation/Count.php
+++ b/cache/stores/mongodb/MongoDB/Operation/Count.php
@@ -18,14 +18,21 @@
 namespace MongoDB\Operation;
 
 use MongoDB\Driver\Command;
+use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
 use MongoDB\Driver\ReadConcern;
 use MongoDB\Driver\ReadPreference;
 use MongoDB\Driver\Server;
 use MongoDB\Driver\Session;
-use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
 use MongoDB\Exception\InvalidArgumentException;
 use MongoDB\Exception\UnexpectedValueException;
 use MongoDB\Exception\UnsupportedException;
+use function current;
+use function is_array;
+use function is_float;
+use function is_integer;
+use function is_object;
+use function is_string;
+use function MongoDB\server_supports_feature;
 
 /**
  * Operation for the count command.
@@ -36,12 +43,22 @@ use MongoDB\Exception\UnsupportedException;
  */
 class Count implements Executable, Explainable
 {
+    /** @var integer */
     private static $wireVersionForCollation = 5;
+
+    /** @var integer */
     private static $wireVersionForReadConcern = 4;
 
+    /** @var string */
     private $databaseName;
+
+    /** @var string */
     private $collectionName;
+
+    /** @var array|object */
     private $filter;
+
+    /** @var array */
     private $options;
 
     /**
@@ -85,7 +102,7 @@ class Count implements Executable, Explainable
      */
     public function __construct($databaseName, $collectionName, $filter = [], array $options = [])
     {
-        if ( ! is_array($filter) && ! is_object($filter)) {
+        if (! is_array($filter) && ! is_object($filter)) {
             throw InvalidArgumentException::invalidType('$filter', $filter, 'array or object');
         }
 
@@ -106,15 +123,15 @@ class Count implements Executable, Explainable
         }
 
         if (isset($options['readConcern']) && ! $options['readConcern'] instanceof ReadConcern) {
-            throw InvalidArgumentException::invalidType('"readConcern" option', $options['readConcern'], 'MongoDB\Driver\ReadConcern');
+            throw InvalidArgumentException::invalidType('"readConcern" option', $options['readConcern'], ReadConcern::class);
         }
 
         if (isset($options['readPreference']) && ! $options['readPreference'] instanceof ReadPreference) {
-            throw InvalidArgumentException::invalidType('"readPreference" option', $options['readPreference'], 'MongoDB\Driver\ReadPreference');
+            throw InvalidArgumentException::invalidType('"readPreference" option', $options['readPreference'], ReadPreference::class);
         }
 
         if (isset($options['session']) && ! $options['session'] instanceof Session) {
-            throw InvalidArgumentException::invalidType('"session" option', $options['session'], 'MongoDB\Driver\Session');
+            throw InvalidArgumentException::invalidType('"session" option', $options['session'], Session::class);
         }
 
         if (isset($options['skip']) && ! is_integer($options['skip'])) {
@@ -143,19 +160,24 @@ class Count implements Executable, Explainable
      */
     public function execute(Server $server)
     {
-        if (isset($this->options['collation']) && ! \MongoDB\server_supports_feature($server, self::$wireVersionForCollation)) {
+        if (isset($this->options['collation']) && ! server_supports_feature($server, self::$wireVersionForCollation)) {
             throw UnsupportedException::collationNotSupported();
         }
 
-        if (isset($this->options['readConcern']) && ! \MongoDB\server_supports_feature($server, self::$wireVersionForReadConcern)) {
+        if (isset($this->options['readConcern']) && ! server_supports_feature($server, self::$wireVersionForReadConcern)) {
             throw UnsupportedException::readConcernNotSupported();
         }
 
+        $inTransaction = isset($this->options['session']) && $this->options['session']->isInTransaction();
+        if ($inTransaction && isset($this->options['readConcern'])) {
+            throw UnsupportedException::readConcernNotSupportedInTransaction();
+        }
+
         $cursor = $server->executeReadCommand($this->databaseName, new Command($this->createCommandDocument()), $this->createOptions());
         $result = current($cursor->toArray());
 
         // Older server versions may return a float
-        if ( ! isset($result->n) || ! (is_integer($result->n) || is_float($result->n))) {
+        if (! isset($result->n) || ! (is_integer($result->n) || is_float($result->n))) {
             throw new UnexpectedValueException('count command did not return a numeric "n" value');
         }
 
@@ -176,7 +198,7 @@ class Count implements Executable, Explainable
     {
         $cmd = ['count' => $this->collectionName];
 
-        if ( ! empty($this->filter)) {
+        if (! empty($this->filter)) {
             $cmd['query'] = (object) $this->filter;
         }
 
diff --git a/cache/stores/mongodb/MongoDB/Operation/CountDocuments.php b/cache/stores/mongodb/MongoDB/Operation/CountDocuments.php
index d79bd7e1b17..77499e5b73e 100644
--- a/cache/stores/mongodb/MongoDB/Operation/CountDocuments.php
+++ b/cache/stores/mongodb/MongoDB/Operation/CountDocuments.php
@@ -17,15 +17,18 @@
 
 namespace MongoDB\Operation;
 
-use MongoDB\Driver\Command;
-use MongoDB\Driver\ReadConcern;
-use MongoDB\Driver\ReadPreference;
-use MongoDB\Driver\Server;
-use MongoDB\Driver\Session;
 use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
+use MongoDB\Driver\Server;
 use MongoDB\Exception\InvalidArgumentException;
 use MongoDB\Exception\UnexpectedValueException;
 use MongoDB\Exception\UnsupportedException;
+use function array_intersect_key;
+use function count;
+use function current;
+use function is_array;
+use function is_float;
+use function is_integer;
+use function is_object;
 
 /**
  * Operation for obtaining an exact count of documents in a collection
@@ -36,13 +39,23 @@ use MongoDB\Exception\UnsupportedException;
  */
 class CountDocuments implements Executable
 {
-    private static $wireVersionForCollation = 5;
-    private static $wireVersionForReadConcern = 4;
-
+    /** @var string */
     private $databaseName;
+
+    /** @var string */
     private $collectionName;
+
+    /** @var array|object */
     private $filter;
-    private $options;
+
+    /** @var array */
+    private $aggregateOptions;
+
+    /** @var array */
+    private $countOptions;
+
+    /** @var Aggregate */
+    private $aggregate;
 
     /**
      * Constructs an aggregate command for counting documents
@@ -85,50 +98,26 @@ class CountDocuments implements Executable
      */
     public function __construct($databaseName, $collectionName, $filter, array $options = [])
     {
-        if ( ! is_array($filter) && ! is_object($filter)) {
+        if (! is_array($filter) && ! is_object($filter)) {
             throw InvalidArgumentException::invalidType('$filter', $filter, 'array or object');
         }
 
-        if (isset($options['collation']) && ! is_array($options['collation']) && ! is_object($options['collation'])) {
-            throw InvalidArgumentException::invalidType('"collation" option', $options['collation'], 'array or object');
-        }
-
-        if (isset($options['hint']) && ! is_string($options['hint']) && ! is_array($options['hint']) && ! is_object($options['hint'])) {
-            throw InvalidArgumentException::invalidType('"hint" option', $options['hint'], 'string or array or object');
-        }
-
         if (isset($options['limit']) && ! is_integer($options['limit'])) {
             throw InvalidArgumentException::invalidType('"limit" option', $options['limit'], 'integer');
         }
 
-        if (isset($options['maxTimeMS']) && ! is_integer($options['maxTimeMS'])) {
-            throw InvalidArgumentException::invalidType('"maxTimeMS" option', $options['maxTimeMS'], 'integer');
-        }
-
-        if (isset($options['readConcern']) && ! $options['readConcern'] instanceof ReadConcern) {
-            throw InvalidArgumentException::invalidType('"readConcern" option', $options['readConcern'], 'MongoDB\Driver\ReadConcern');
-        }
-
-        if (isset($options['readPreference']) && ! $options['readPreference'] instanceof ReadPreference) {
-            throw InvalidArgumentException::invalidType('"readPreference" option', $options['readPreference'], 'MongoDB\Driver\ReadPreference');
-        }
-
-        if (isset($options['session']) && ! $options['session'] instanceof Session) {
-            throw InvalidArgumentException::invalidType('"session" option', $options['session'], 'MongoDB\Driver\Session');
-        }
-
         if (isset($options['skip']) && ! is_integer($options['skip'])) {
             throw InvalidArgumentException::invalidType('"skip" option', $options['skip'], 'integer');
         }
 
-        if (isset($options['readConcern']) && $options['readConcern']->isDefault()) {
-            unset($options['readConcern']);
-        }
-
         $this->databaseName = (string) $databaseName;
         $this->collectionName = (string) $collectionName;
         $this->filter = $filter;
-        $this->options = $options;
+
+        $this->aggregateOptions = array_intersect_key($options, ['collation' => 1, 'hint' => 1, 'maxTimeMS' => 1, 'readConcern' => 1, 'readPreference' => 1, 'session' => 1]);
+        $this->countOptions = array_intersect_key($options, ['limit' => 1, 'skip' => 1]);
+
+        $this->aggregate = $this->createAggregate();
     }
 
     /**
@@ -143,15 +132,7 @@ class CountDocuments implements Executable
      */
     public function execute(Server $server)
     {
-        if (isset($this->options['collation']) && ! \MongoDB\server_supports_feature($server, self::$wireVersionForCollation)) {
-            throw UnsupportedException::collationNotSupported();
-        }
-
-        if (isset($this->options['readConcern']) && ! \MongoDB\server_supports_feature($server, self::$wireVersionForReadConcern)) {
-            throw UnsupportedException::readConcernNotSupported();
-        }
-
-        $cursor = $server->executeReadCommand($this->databaseName, new Command($this->createCommandDocument()), $this->createOptions());
+        $cursor = $this->aggregate->execute($server);
         $allResults = $cursor->toArray();
 
         /* If there are no documents to count, the aggregation pipeline has no items to group, and
@@ -161,7 +142,7 @@ class CountDocuments implements Executable
         }
 
         $result = current($allResults);
-        if ( ! isset($result->n) || ! (is_integer($result->n) || is_float($result->n))) {
+        if (! isset($result->n) || ! (is_integer($result->n) || is_float($result->n))) {
             throw new UnexpectedValueException('count command did not return a numeric "n" value');
         }
 
@@ -169,69 +150,24 @@ class CountDocuments implements Executable
     }
 
     /**
-     * Create the count command document.
-     *
-     * @return array
+     * @return Aggregate
      */
-    private function createCommandDocument()
+    private function createAggregate()
     {
         $pipeline = [
-            ['$match' => (object) $this->filter]
+            ['$match' => (object) $this->filter],
         ];
 
-        if (isset($this->options['skip'])) {
-            $pipeline[] = ['$skip' => $this->options['skip']];
+        if (isset($this->countOptions['skip'])) {
+            $pipeline[] = ['$skip' => $this->countOptions['skip']];
         }
 
-        if (isset($this->options['limit'])) {
-            $pipeline[] = ['$limit' => $this->options['limit']];
+        if (isset($this->countOptions['limit'])) {
+            $pipeline[] = ['$limit' => $this->countOptions['limit']];
         }
 
-        $pipeline[] = ['$group' => ['_id' => null, 'n' => ['$sum' => 1]]];
+        $pipeline[] = ['$group' => ['_id' => 1, 'n' => ['$sum' => 1]]];
 
-        $cmd = [
-            'aggregate' => $this->collectionName,
-            'pipeline' => $pipeline,
-            'cursor' => (object) [],
-        ];
-
-        if (isset($this->options['collation'])) {
-            $cmd['collation'] = (object) $this->options['collation'];
-        }
-
-        if (isset($this->options['hint'])) {
-            $cmd['hint'] = is_array($this->options['hint']) ? (object) $this->options['hint'] : $this->options['hint'];
-        }
-
-        if (isset($this->options['maxTimeMS'])) {
-            $cmd['maxTimeMS'] = $this->options['maxTimeMS'];
-        }
-
-        return $cmd;
-    }
-
-    /**
-     * Create options for executing the command.
-     *
-     * @see http://php.net/manual/en/mongodb-driver-server.executereadcommand.php
-     * @return array
-     */
-    private function createOptions()
-    {
-        $options = [];
-
-        if (isset($this->options['readConcern'])) {
-            $options['readConcern'] = $this->options['readConcern'];
-        }
-
-        if (isset($this->options['readPreference'])) {
-            $options['readPreference'] = $this->options['readPreference'];
-        }
-
-        if (isset($this->options['session'])) {
-            $options['session'] = $this->options['session'];
-        }
-
-        return $options;
+        return new Aggregate($this->databaseName, $this->collectionName, $pipeline, $this->aggregateOptions);
     }
 }
diff --git a/cache/stores/mongodb/MongoDB/Operation/CreateCollection.php b/cache/stores/mongodb/MongoDB/Operation/CreateCollection.php
index b5b90867ead..98fac51d603 100644
--- a/cache/stores/mongodb/MongoDB/Operation/CreateCollection.php
+++ b/cache/stores/mongodb/MongoDB/Operation/CreateCollection.php
@@ -18,12 +18,21 @@
 namespace MongoDB\Operation;
 
 use MongoDB\Driver\Command;
+use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
 use MongoDB\Driver\Server;
 use MongoDB\Driver\Session;
 use MongoDB\Driver\WriteConcern;
-use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
 use MongoDB\Exception\InvalidArgumentException;
 use MongoDB\Exception\UnsupportedException;
+use function current;
+use function is_array;
+use function is_bool;
+use function is_integer;
+use function is_object;
+use function is_string;
+use function MongoDB\server_supports_feature;
+use function trigger_error;
+use const E_USER_DEPRECATED;
 
 /**
  * Operation for the create command.
@@ -37,11 +46,19 @@ class CreateCollection implements Executable
     const USE_POWER_OF_2_SIZES = 1;
     const NO_PADDING = 2;
 
+    /** @var integer */
     private static $wireVersionForCollation = 5;
+
+    /** @var integer */
     private static $wireVersionForWriteConcern = 5;
 
+    /** @var string */
     private $databaseName;
+
+    /** @var string */
     private $collectionName;
+
+    /** @var array */
     private $options = [];
 
     /**
@@ -139,7 +156,7 @@ class CreateCollection implements Executable
         }
 
         if (isset($options['session']) && ! $options['session'] instanceof Session) {
-            throw InvalidArgumentException::invalidType('"session" option', $options['session'], 'MongoDB\Driver\Session');
+            throw InvalidArgumentException::invalidType('"session" option', $options['session'], Session::class);
         }
 
         if (isset($options['size']) && ! is_integer($options['size'])) {
@@ -167,7 +184,7 @@ class CreateCollection implements Executable
         }
 
         if (isset($options['writeConcern']) && ! $options['writeConcern'] instanceof WriteConcern) {
-            throw InvalidArgumentException::invalidType('"writeConcern" option', $options['writeConcern'], 'MongoDB\Driver\WriteConcern');
+            throw InvalidArgumentException::invalidType('"writeConcern" option', $options['writeConcern'], WriteConcern::class);
         }
 
         if (isset($options['writeConcern']) && $options['writeConcern']->isDefault()) {
@@ -194,11 +211,11 @@ class CreateCollection implements Executable
      */
     public function execute(Server $server)
     {
-        if (isset($this->options['collation']) && ! \MongoDB\server_supports_feature($server, self::$wireVersionForCollation)) {
+        if (isset($this->options['collation']) && ! server_supports_feature($server, self::$wireVersionForCollation)) {
             throw UnsupportedException::collationNotSupported();
         }
 
-        if (isset($this->options['writeConcern']) && ! \MongoDB\server_supports_feature($server, self::$wireVersionForWriteConcern)) {
+        if (isset($this->options['writeConcern']) && ! server_supports_feature($server, self::$wireVersionForWriteConcern)) {
             throw UnsupportedException::writeConcernNotSupported();
         }
 
diff --git a/cache/stores/mongodb/MongoDB/Operation/CreateIndexes.php b/cache/stores/mongodb/MongoDB/Operation/CreateIndexes.php
index 07050f54f8f..bf4dea3d6b1 100644
--- a/cache/stores/mongodb/MongoDB/Operation/CreateIndexes.php
+++ b/cache/stores/mongodb/MongoDB/Operation/CreateIndexes.php
@@ -17,15 +17,19 @@
 
 namespace MongoDB\Operation;
 
-use MongoDB\Driver\BulkWrite as Bulk;
 use MongoDB\Driver\Command;
+use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
 use MongoDB\Driver\Server;
 use MongoDB\Driver\Session;
 use MongoDB\Driver\WriteConcern;
-use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
 use MongoDB\Exception\InvalidArgumentException;
 use MongoDB\Exception\UnsupportedException;
 use MongoDB\Model\IndexInput;
+use function array_map;
+use function is_array;
+use function is_integer;
+use function MongoDB\server_supports_feature;
+use function sprintf;
 
 /**
  * Operation for the createIndexes command.
@@ -37,13 +41,25 @@ use MongoDB\Model\IndexInput;
  */
 class CreateIndexes implements Executable
 {
+    /** @var integer */
     private static $wireVersionForCollation = 5;
+
+    /** @var integer */
     private static $wireVersionForWriteConcern = 5;
 
+    /** @var string */
     private $databaseName;
+
+    /** @var string */
     private $collectionName;
+
+    /** @var array */
     private $indexes = [];
+
+    /** @var boolean */
     private $isCollationUsed = false;
+
+    /** @var array */
     private $options = [];
 
     /**
@@ -82,11 +98,11 @@ class CreateIndexes implements Executable
                 throw new InvalidArgumentException(sprintf('$indexes is not a list (unexpected index: "%s")', $i));
             }
 
-            if ( ! is_array($index)) {
+            if (! is_array($index)) {
                 throw InvalidArgumentException::invalidType(sprintf('$index[%d]', $i), $index, 'array');
             }
 
-            if ( ! isset($index['ns'])) {
+            if (! isset($index['ns'])) {
                 $index['ns'] = $databaseName . '.' . $collectionName;
             }
 
@@ -99,16 +115,16 @@ class CreateIndexes implements Executable
             $expectedIndex += 1;
         }
 
-        if (isset($options['maxTimeMS']) && !is_integer($options['maxTimeMS'])) {
+        if (isset($options['maxTimeMS']) && ! is_integer($options['maxTimeMS'])) {
             throw InvalidArgumentException::invalidType('"maxTimeMS" option', $options['maxTimeMS'], 'integer');
         }
 
         if (isset($options['session']) && ! $options['session'] instanceof Session) {
-            throw InvalidArgumentException::invalidType('"session" option', $options['session'], 'MongoDB\Driver\Session');
+            throw InvalidArgumentException::invalidType('"session" option', $options['session'], Session::class);
         }
 
         if (isset($options['writeConcern']) && ! $options['writeConcern'] instanceof WriteConcern) {
-            throw InvalidArgumentException::invalidType('"writeConcern" option', $options['writeConcern'], 'MongoDB\Driver\WriteConcern');
+            throw InvalidArgumentException::invalidType('"writeConcern" option', $options['writeConcern'], WriteConcern::class);
         }
 
         if (isset($options['writeConcern']) && $options['writeConcern']->isDefault()) {
@@ -131,17 +147,24 @@ class CreateIndexes implements Executable
      */
     public function execute(Server $server)
     {
-        if ($this->isCollationUsed && ! \MongoDB\server_supports_feature($server, self::$wireVersionForCollation)) {
+        if ($this->isCollationUsed && ! server_supports_feature($server, self::$wireVersionForCollation)) {
             throw UnsupportedException::collationNotSupported();
         }
 
-        if (isset($this->options['writeConcern']) && ! \MongoDB\server_supports_feature($server, self::$wireVersionForWriteConcern)) {
+        if (isset($this->options['writeConcern']) && ! server_supports_feature($server, self::$wireVersionForWriteConcern)) {
             throw UnsupportedException::writeConcernNotSupported();
         }
 
+        $inTransaction = isset($this->options['session']) && $this->options['session']->isInTransaction();
+        if ($inTransaction && isset($this->options['writeConcern'])) {
+            throw UnsupportedException::writeConcernNotSupportedInTransaction();
+        }
+
         $this->executeCommand($server);
 
-        return array_map(function(IndexInput $index) { return (string) $index; }, $this->indexes);
+        return array_map(function (IndexInput $index) {
+            return (string) $index;
+        }, $this->indexes);
     }
 
     /**
diff --git a/cache/stores/mongodb/MongoDB/Operation/DatabaseCommand.php b/cache/stores/mongodb/MongoDB/Operation/DatabaseCommand.php
index aa0a8270ccd..af0f7624898 100644
--- a/cache/stores/mongodb/MongoDB/Operation/DatabaseCommand.php
+++ b/cache/stores/mongodb/MongoDB/Operation/DatabaseCommand.php
@@ -23,6 +23,8 @@ use MongoDB\Driver\ReadPreference;
 use MongoDB\Driver\Server;
 use MongoDB\Driver\Session;
 use MongoDB\Exception\InvalidArgumentException;
+use function is_array;
+use function is_object;
 
 /**
  * Operation for executing a database command.
@@ -32,8 +34,13 @@ use MongoDB\Exception\InvalidArgumentException;
  */
 class DatabaseCommand implements Executable
 {
+    /** @var string */
     private $databaseName;
+
+    /** @var array|Command|object */
     private $command;
+
+    /** @var array */
     private $options;
 
     /**
@@ -54,23 +61,23 @@ class DatabaseCommand implements Executable
      *  * typeMap (array): Type map for BSON deserialization. This will be
      *    applied to the returned Cursor (it is not sent to the server).
      *
-     * @param string       $databaseName   Database name
-     * @param array|object $command        Command document
-     * @param array        $options        Options for command execution
+     * @param string       $databaseName Database name
+     * @param array|object $command      Command document
+     * @param array        $options      Options for command execution
      * @throws InvalidArgumentException for parameter/option parsing errors
      */
     public function __construct($databaseName, $command, array $options = [])
     {
-        if ( ! is_array($command) && ! is_object($command)) {
+        if (! is_array($command) && ! is_object($command)) {
             throw InvalidArgumentException::invalidType('$command', $command, 'array or object');
         }
 
         if (isset($options['readPreference']) && ! $options['readPreference'] instanceof ReadPreference) {
-            throw InvalidArgumentException::invalidType('"readPreference" option', $options['readPreference'], 'MongoDB\Driver\ReadPreference');
+            throw InvalidArgumentException::invalidType('"readPreference" option', $options['readPreference'], ReadPreference::class);
         }
 
         if (isset($options['session']) && ! $options['session'] instanceof Session) {
-            throw InvalidArgumentException::invalidType('"session" option', $options['session'], 'MongoDB\Driver\Session');
+            throw InvalidArgumentException::invalidType('"session" option', $options['session'], Session::class);
         }
 
         if (isset($options['typeMap']) && ! is_array($options['typeMap'])) {
@@ -78,7 +85,7 @@ class DatabaseCommand implements Executable
         }
 
         $this->databaseName = (string) $databaseName;
-        $this->command = ($command instanceof Command) ? $command : new Command($command);
+        $this->command = $command instanceof Command ? $command : new Command($command);
         $this->options = $options;
     }
 
diff --git a/cache/stores/mongodb/MongoDB/Operation/Delete.php b/cache/stores/mongodb/MongoDB/Operation/Delete.php
index 496c3dda31b..181351b0e97 100644
--- a/cache/stores/mongodb/MongoDB/Operation/Delete.php
+++ b/cache/stores/mongodb/MongoDB/Operation/Delete.php
@@ -19,12 +19,15 @@ namespace MongoDB\Operation;
 
 use MongoDB\DeleteResult;
 use MongoDB\Driver\BulkWrite as Bulk;
+use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
 use MongoDB\Driver\Server;
 use MongoDB\Driver\Session;
 use MongoDB\Driver\WriteConcern;
-use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
 use MongoDB\Exception\InvalidArgumentException;
 use MongoDB\Exception\UnsupportedException;
+use function is_array;
+use function is_object;
+use function MongoDB\server_supports_feature;
 
 /**
  * Operation for the delete command.
@@ -37,12 +40,22 @@ use MongoDB\Exception\UnsupportedException;
  */
 class Delete implements Executable, Explainable
 {
+    /** @var integer */
     private static $wireVersionForCollation = 5;
 
+    /** @var string */
     private $databaseName;
+
+    /** @var string */
     private $collectionName;
+
+    /** @var array|object */
     private $filter;
+
+    /** @var integer */
     private $limit;
+
+    /** @var array */
     private $options;
 
     /**
@@ -72,7 +85,7 @@ class Delete implements Executable, Explainable
      */
     public function __construct($databaseName, $collectionName, $filter, $limit, array $options = [])
     {
-        if ( ! is_array($filter) && ! is_object($filter)) {
+        if (! is_array($filter) && ! is_object($filter)) {
             throw InvalidArgumentException::invalidType('$filter', $filter, 'array or object');
         }
 
@@ -85,11 +98,11 @@ class Delete implements Executable, Explainable
         }
 
         if (isset($options['session']) && ! $options['session'] instanceof Session) {
-            throw InvalidArgumentException::invalidType('"session" option', $options['session'], 'MongoDB\Driver\Session');
+            throw InvalidArgumentException::invalidType('"session" option', $options['session'], Session::class);
         }
 
         if (isset($options['writeConcern']) && ! $options['writeConcern'] instanceof WriteConcern) {
-            throw InvalidArgumentException::invalidType('"writeConcern" option', $options['writeConcern'], 'MongoDB\Driver\WriteConcern');
+            throw InvalidArgumentException::invalidType('"writeConcern" option', $options['writeConcern'], WriteConcern::class);
         }
 
         if (isset($options['writeConcern']) && $options['writeConcern']->isDefault()) {
@@ -113,10 +126,15 @@ class Delete implements Executable, Explainable
      */
     public function execute(Server $server)
     {
-        if (isset($this->options['collation']) && ! \MongoDB\server_supports_feature($server, self::$wireVersionForCollation)) {
+        if (isset($this->options['collation']) && ! server_supports_feature($server, self::$wireVersionForCollation)) {
             throw UnsupportedException::collationNotSupported();
         }
 
+        $inTransaction = isset($this->options['session']) && $this->options['session']->isInTransaction();
+        if ($inTransaction && isset($this->options['writeConcern'])) {
+            throw UnsupportedException::writeConcernNotSupportedInTransaction();
+        }
+
         $bulk = new Bulk();
         $bulk->delete($this->filter, $this->createDeleteOptions());
 
diff --git a/cache/stores/mongodb/MongoDB/Operation/DeleteMany.php b/cache/stores/mongodb/MongoDB/Operation/DeleteMany.php
index 5b32d0315e6..96c8031e9cc 100644
--- a/cache/stores/mongodb/MongoDB/Operation/DeleteMany.php
+++ b/cache/stores/mongodb/MongoDB/Operation/DeleteMany.php
@@ -18,8 +18,8 @@
 namespace MongoDB\Operation;
 
 use MongoDB\DeleteResult;
-use MongoDB\Driver\Server;
 use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
+use MongoDB\Driver\Server;
 use MongoDB\Exception\InvalidArgumentException;
 use MongoDB\Exception\UnsupportedException;
 
@@ -32,6 +32,7 @@ use MongoDB\Exception\UnsupportedException;
  */
 class DeleteMany implements Executable, Explainable
 {
+    /** @var Delete */
     private $delete;
 
     /**
diff --git a/cache/stores/mongodb/MongoDB/Operation/DeleteOne.php b/cache/stores/mongodb/MongoDB/Operation/DeleteOne.php
index e7d47ded43a..3377a66d8a6 100644
--- a/cache/stores/mongodb/MongoDB/Operation/DeleteOne.php
+++ b/cache/stores/mongodb/MongoDB/Operation/DeleteOne.php
@@ -18,8 +18,8 @@
 namespace MongoDB\Operation;
 
 use MongoDB\DeleteResult;
-use MongoDB\Driver\Server;
 use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
+use MongoDB\Driver\Server;
 use MongoDB\Exception\InvalidArgumentException;
 use MongoDB\Exception\UnsupportedException;
 
@@ -32,6 +32,7 @@ use MongoDB\Exception\UnsupportedException;
  */
 class DeleteOne implements Executable, Explainable
 {
+    /** @var Delete */
     private $delete;
 
     /**
diff --git a/cache/stores/mongodb/MongoDB/Operation/Distinct.php b/cache/stores/mongodb/MongoDB/Operation/Distinct.php
index 8e7f39efd42..f8e169ca71c 100644
--- a/cache/stores/mongodb/MongoDB/Operation/Distinct.php
+++ b/cache/stores/mongodb/MongoDB/Operation/Distinct.php
@@ -18,14 +18,20 @@
 namespace MongoDB\Operation;
 
 use MongoDB\Driver\Command;
+use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
 use MongoDB\Driver\ReadConcern;
 use MongoDB\Driver\ReadPreference;
 use MongoDB\Driver\Server;
 use MongoDB\Driver\Session;
-use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
 use MongoDB\Exception\InvalidArgumentException;
 use MongoDB\Exception\UnexpectedValueException;
 use MongoDB\Exception\UnsupportedException;
+use function current;
+use function is_array;
+use function is_integer;
+use function is_object;
+use function MongoDB\create_field_path_type_map;
+use function MongoDB\server_supports_feature;
 
 /**
  * Operation for the distinct command.
@@ -36,13 +42,25 @@ use MongoDB\Exception\UnsupportedException;
  */
 class Distinct implements Executable, Explainable
 {
+    /** @var integer */
     private static $wireVersionForCollation = 5;
+
+    /** @var integer */
     private static $wireVersionForReadConcern = 4;
 
+    /** @var string */
     private $databaseName;
+
+    /** @var string */
     private $collectionName;
+
+    /** @var string */
     private $fieldName;
+
+    /** @var array|object */
     private $filter;
+
+    /** @var array */
     private $options;
 
     /**
@@ -69,6 +87,8 @@ class Distinct implements Executable, Explainable
      *
      *    Sessions are not supported for server versions < 3.6.
      *
+     *  * typeMap (array): Type map for BSON deserialization.
+     *
      * @param string       $databaseName   Database name
      * @param string       $collectionName Collection name
      * @param string       $fieldName      Field for which to return distinct values
@@ -78,7 +98,7 @@ class Distinct implements Executable, Explainable
      */
     public function __construct($databaseName, $collectionName, $fieldName, $filter = [], array $options = [])
     {
-        if ( ! is_array($filter) && ! is_object($filter)) {
+        if (! is_array($filter) && ! is_object($filter)) {
             throw InvalidArgumentException::invalidType('$filter', $filter, 'array or object');
         }
 
@@ -91,15 +111,19 @@ class Distinct implements Executable, Explainable
         }
 
         if (isset($options['readConcern']) && ! $options['readConcern'] instanceof ReadConcern) {
-            throw InvalidArgumentException::invalidType('"readConcern" option', $options['readConcern'], 'MongoDB\Driver\ReadConcern');
+            throw InvalidArgumentException::invalidType('"readConcern" option', $options['readConcern'], ReadConcern::class);
         }
 
         if (isset($options['readPreference']) && ! $options['readPreference'] instanceof ReadPreference) {
-            throw InvalidArgumentException::invalidType('"readPreference" option', $options['readPreference'], 'MongoDB\Driver\ReadPreference');
+            throw InvalidArgumentException::invalidType('"readPreference" option', $options['readPreference'], ReadPreference::class);
         }
 
         if (isset($options['session']) && ! $options['session'] instanceof Session) {
-            throw InvalidArgumentException::invalidType('"session" option', $options['session'], 'MongoDB\Driver\Session');
+            throw InvalidArgumentException::invalidType('"session" option', $options['session'], Session::class);
+        }
+
+        if (isset($options['typeMap']) && ! is_array($options['typeMap'])) {
+            throw InvalidArgumentException::invalidType('"typeMap" option', $options['typeMap'], 'array');
         }
 
         if (isset($options['readConcern']) && $options['readConcern']->isDefault()) {
@@ -125,18 +149,28 @@ class Distinct implements Executable, Explainable
      */
     public function execute(Server $server)
     {
-        if (isset($this->options['collation']) && ! \MongoDB\server_supports_feature($server, self::$wireVersionForCollation)) {
+        if (isset($this->options['collation']) && ! server_supports_feature($server, self::$wireVersionForCollation)) {
             throw UnsupportedException::collationNotSupported();
         }
 
-        if (isset($this->options['readConcern']) && ! \MongoDB\server_supports_feature($server, self::$wireVersionForReadConcern)) {
+        if (isset($this->options['readConcern']) && ! server_supports_feature($server, self::$wireVersionForReadConcern)) {
             throw UnsupportedException::readConcernNotSupported();
         }
 
+        $inTransaction = isset($this->options['session']) && $this->options['session']->isInTransaction();
+        if ($inTransaction && isset($this->options['readConcern'])) {
+            throw UnsupportedException::readConcernNotSupportedInTransaction();
+        }
+
         $cursor = $server->executeReadCommand($this->databaseName, new Command($this->createCommandDocument()), $this->createOptions());
+
+        if (isset($this->options['typeMap'])) {
+            $cursor->setTypeMap(create_field_path_type_map($this->options['typeMap'], 'values.$'));
+        }
+
         $result = current($cursor->toArray());
 
-        if ( ! isset($result->values) || ! is_array($result->values)) {
+        if (! isset($result->values) || ! is_array($result->values)) {
             throw new UnexpectedValueException('distinct command did not return a "values" array');
         }
 
@@ -160,7 +194,7 @@ class Distinct implements Executable, Explainable
             'key' => $this->fieldName,
         ];
 
-        if ( ! empty($this->filter)) {
+        if (! empty($this->filter)) {
             $cmd['query'] = (object) $this->filter;
         }
 
diff --git a/cache/stores/mongodb/MongoDB/Operation/DropCollection.php b/cache/stores/mongodb/MongoDB/Operation/DropCollection.php
index 1ee66fa926c..fb328cba10f 100644
--- a/cache/stores/mongodb/MongoDB/Operation/DropCollection.php
+++ b/cache/stores/mongodb/MongoDB/Operation/DropCollection.php
@@ -18,12 +18,15 @@
 namespace MongoDB\Operation;
 
 use MongoDB\Driver\Command;
+use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
 use MongoDB\Driver\Server;
 use MongoDB\Driver\Session;
 use MongoDB\Driver\WriteConcern;
-use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
 use MongoDB\Exception\InvalidArgumentException;
 use MongoDB\Exception\UnsupportedException;
+use function current;
+use function is_array;
+use function MongoDB\server_supports_feature;
 
 /**
  * Operation for the drop command.
@@ -35,11 +38,19 @@ use MongoDB\Exception\UnsupportedException;
  */
 class DropCollection implements Executable
 {
+    /** @var string */
     private static $errorMessageNamespaceNotFound = 'ns not found';
+
+    /** @var integer */
     private static $wireVersionForWriteConcern = 5;
 
+    /** @var string */
     private $databaseName;
+
+    /** @var string */
     private $collectionName;
+
+    /** @var array */
     private $options;
 
     /**
@@ -67,7 +78,7 @@ class DropCollection implements Executable
     public function __construct($databaseName, $collectionName, array $options = [])
     {
         if (isset($options['session']) && ! $options['session'] instanceof Session) {
-            throw InvalidArgumentException::invalidType('"session" option', $options['session'], 'MongoDB\Driver\Session');
+            throw InvalidArgumentException::invalidType('"session" option', $options['session'], Session::class);
         }
 
         if (isset($options['typeMap']) && ! is_array($options['typeMap'])) {
@@ -75,7 +86,7 @@ class DropCollection implements Executable
         }
 
         if (isset($options['writeConcern']) && ! $options['writeConcern'] instanceof WriteConcern) {
-            throw InvalidArgumentException::invalidType('"writeConcern" option', $options['writeConcern'], 'MongoDB\Driver\WriteConcern');
+            throw InvalidArgumentException::invalidType('"writeConcern" option', $options['writeConcern'], WriteConcern::class);
         }
 
         if (isset($options['writeConcern']) && $options['writeConcern']->isDefault()) {
@@ -98,10 +109,15 @@ class DropCollection implements Executable
      */
     public function execute(Server $server)
     {
-        if (isset($this->options['writeConcern']) && ! \MongoDB\server_supports_feature($server, self::$wireVersionForWriteConcern)) {
+        if (isset($this->options['writeConcern']) && ! server_supports_feature($server, self::$wireVersionForWriteConcern)) {
             throw UnsupportedException::writeConcernNotSupported();
         }
 
+        $inTransaction = isset($this->options['session']) && $this->options['session']->isInTransaction();
+        if ($inTransaction && isset($this->options['writeConcern'])) {
+            throw UnsupportedException::writeConcernNotSupportedInTransaction();
+        }
+
         $command = new Command(['drop' => $this->collectionName]);
 
         try {
diff --git a/cache/stores/mongodb/MongoDB/Operation/DropDatabase.php b/cache/stores/mongodb/MongoDB/Operation/DropDatabase.php
index ac1e90319a3..5a4335a7d8d 100644
--- a/cache/stores/mongodb/MongoDB/Operation/DropDatabase.php
+++ b/cache/stores/mongodb/MongoDB/Operation/DropDatabase.php
@@ -18,12 +18,15 @@
 namespace MongoDB\Operation;
 
 use MongoDB\Driver\Command;
+use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
 use MongoDB\Driver\Server;
 use MongoDB\Driver\Session;
 use MongoDB\Driver\WriteConcern;
-use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
 use MongoDB\Exception\InvalidArgumentException;
 use MongoDB\Exception\UnsupportedException;
+use function current;
+use function is_array;
+use function MongoDB\server_supports_feature;
 
 /**
  * Operation for the dropDatabase command.
@@ -35,9 +38,13 @@ use MongoDB\Exception\UnsupportedException;
  */
 class DropDatabase implements Executable
 {
+    /** @var integer */
     private static $wireVersionForWriteConcern = 5;
 
+    /** @var string */
     private $databaseName;
+
+    /** @var array */
     private $options;
 
     /**
@@ -64,7 +71,7 @@ class DropDatabase implements Executable
     public function __construct($databaseName, array $options = [])
     {
         if (isset($options['session']) && ! $options['session'] instanceof Session) {
-            throw InvalidArgumentException::invalidType('"session" option', $options['session'], 'MongoDB\Driver\Session');
+            throw InvalidArgumentException::invalidType('"session" option', $options['session'], Session::class);
         }
 
         if (isset($options['typeMap']) && ! is_array($options['typeMap'])) {
@@ -72,7 +79,7 @@ class DropDatabase implements Executable
         }
 
         if (isset($options['writeConcern']) && ! $options['writeConcern'] instanceof WriteConcern) {
-            throw InvalidArgumentException::invalidType('"writeConcern" option', $options['writeConcern'], 'MongoDB\Driver\WriteConcern');
+            throw InvalidArgumentException::invalidType('"writeConcern" option', $options['writeConcern'], WriteConcern::class);
         }
 
         if (isset($options['writeConcern']) && $options['writeConcern']->isDefault()) {
@@ -94,7 +101,7 @@ class DropDatabase implements Executable
      */
     public function execute(Server $server)
     {
-        if (isset($this->options['writeConcern']) && ! \MongoDB\server_supports_feature($server, self::$wireVersionForWriteConcern)) {
+        if (isset($this->options['writeConcern']) && ! server_supports_feature($server, self::$wireVersionForWriteConcern)) {
             throw UnsupportedException::writeConcernNotSupported();
         }
 
diff --git a/cache/stores/mongodb/MongoDB/Operation/DropIndexes.php b/cache/stores/mongodb/MongoDB/Operation/DropIndexes.php
index 9dae54e911c..322e3b10f9a 100644
--- a/cache/stores/mongodb/MongoDB/Operation/DropIndexes.php
+++ b/cache/stores/mongodb/MongoDB/Operation/DropIndexes.php
@@ -18,12 +18,16 @@
 namespace MongoDB\Operation;
 
 use MongoDB\Driver\Command;
+use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
 use MongoDB\Driver\Server;
 use MongoDB\Driver\Session;
 use MongoDB\Driver\WriteConcern;
-use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
 use MongoDB\Exception\InvalidArgumentException;
 use MongoDB\Exception\UnsupportedException;
+use function current;
+use function is_array;
+use function is_integer;
+use function MongoDB\server_supports_feature;
 
 /**
  * Operation for the dropIndexes command.
@@ -34,11 +38,19 @@ use MongoDB\Exception\UnsupportedException;
  */
 class DropIndexes implements Executable
 {
+    /** @var integer */
     private static $wireVersionForWriteConcern = 5;
 
+    /** @var string */
     private $databaseName;
+
+    /** @var string */
     private $collectionName;
+
+    /** @var string */
     private $indexName;
+
+    /** @var array */
     private $options;
 
     /**
@@ -80,7 +92,7 @@ class DropIndexes implements Executable
         }
 
         if (isset($options['session']) && ! $options['session'] instanceof Session) {
-            throw InvalidArgumentException::invalidType('"session" option', $options['session'], 'MongoDB\Driver\Session');
+            throw InvalidArgumentException::invalidType('"session" option', $options['session'], Session::class);
         }
 
         if (isset($options['typeMap']) && ! is_array($options['typeMap'])) {
@@ -88,7 +100,7 @@ class DropIndexes implements Executable
         }
 
         if (isset($options['writeConcern']) && ! $options['writeConcern'] instanceof WriteConcern) {
-            throw InvalidArgumentException::invalidType('"writeConcern" option', $options['writeConcern'], 'MongoDB\Driver\WriteConcern');
+            throw InvalidArgumentException::invalidType('"writeConcern" option', $options['writeConcern'], WriteConcern::class);
         }
 
         if (isset($options['writeConcern']) && $options['writeConcern']->isDefault()) {
@@ -112,10 +124,15 @@ class DropIndexes implements Executable
      */
     public function execute(Server $server)
     {
-        if (isset($this->options['writeConcern']) && ! \MongoDB\server_supports_feature($server, self::$wireVersionForWriteConcern)) {
+        if (isset($this->options['writeConcern']) && ! server_supports_feature($server, self::$wireVersionForWriteConcern)) {
             throw UnsupportedException::writeConcernNotSupported();
         }
 
+        $inTransaction = isset($this->options['session']) && $this->options['session']->isInTransaction();
+        if ($inTransaction && isset($this->options['writeConcern'])) {
+            throw UnsupportedException::writeConcernNotSupportedInTransaction();
+        }
+
         $cursor = $server->executeWriteCommand($this->databaseName, $this->createCommand(), $this->createOptions());
 
         if (isset($this->options['typeMap'])) {
diff --git a/cache/stores/mongodb/MongoDB/Operation/EstimatedDocumentCount.php b/cache/stores/mongodb/MongoDB/Operation/EstimatedDocumentCount.php
index 621608d1900..2e6dd5ca132 100644
--- a/cache/stores/mongodb/MongoDB/Operation/EstimatedDocumentCount.php
+++ b/cache/stores/mongodb/MongoDB/Operation/EstimatedDocumentCount.php
@@ -17,15 +17,12 @@
 
 namespace MongoDB\Operation;
 
-use MongoDB\Driver\Command;
-use MongoDB\Driver\ReadConcern;
-use MongoDB\Driver\ReadPreference;
-use MongoDB\Driver\Server;
-use MongoDB\Driver\Session;
 use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
+use MongoDB\Driver\Server;
 use MongoDB\Exception\InvalidArgumentException;
 use MongoDB\Exception\UnexpectedValueException;
 use MongoDB\Exception\UnsupportedException;
+use function array_intersect_key;
 
 /**
  * Operation for obtaining an estimated count of documents in a collection
@@ -36,13 +33,18 @@ use MongoDB\Exception\UnsupportedException;
  */
 class EstimatedDocumentCount implements Executable, Explainable
 {
-    private static $wireVersionForCollation = 5;
-    private static $wireVersionForReadConcern = 4;
-
+    /** @var string */
     private $databaseName;
+
+    /** @var string */
     private $collectionName;
+
+    /** @var array */
     private $options;
 
+    /** @var Count */
+    private $count;
+
     /**
      * Constructs a count command.
      *
@@ -62,36 +64,18 @@ class EstimatedDocumentCount implements Executable, Explainable
      *
      *    Sessions are not supported for server versions < 3.6.
      *
-     * @param string       $databaseName   Database name
-     * @param string       $collectionName Collection name
-     * @param array        $options        Command options
+     * @param string $databaseName   Database name
+     * @param string $collectionName Collection name
+     * @param array  $options        Command options
      * @throws InvalidArgumentException for parameter/option parsing errors
      */
     public function __construct($databaseName, $collectionName, array $options = [])
     {
-        if (isset($options['maxTimeMS']) && ! is_integer($options['maxTimeMS'])) {
-            throw InvalidArgumentException::invalidType('"maxTimeMS" option', $options['maxTimeMS'], 'integer');
-        }
-
-        if (isset($options['readConcern']) && ! $options['readConcern'] instanceof ReadConcern) {
-            throw InvalidArgumentException::invalidType('"readConcern" option', $options['readConcern'], 'MongoDB\Driver\ReadConcern');
-        }
-
-        if (isset($options['readPreference']) && ! $options['readPreference'] instanceof ReadPreference) {
-            throw InvalidArgumentException::invalidType('"readPreference" option', $options['readPreference'], 'MongoDB\Driver\ReadPreference');
-        }
-
-        if (isset($options['session']) && ! $options['session'] instanceof Session) {
-            throw InvalidArgumentException::invalidType('"session" option', $options['session'], 'MongoDB\Driver\Session');
-        }
-
-        if (isset($options['readConcern']) && $options['readConcern']->isDefault()) {
-            unset($options['readConcern']);
-        }
-
         $this->databaseName = (string) $databaseName;
         $this->collectionName = (string) $collectionName;
-        $this->options = $options;
+        $this->options = array_intersect_key($options, ['maxTimeMS' => 1, 'readConcern' => 1, 'readPreference' => 1, 'session' => 1]);
+
+        $this->count = $this->createCount();
     }
 
     /**
@@ -106,68 +90,19 @@ class EstimatedDocumentCount implements Executable, Explainable
      */
     public function execute(Server $server)
     {
-        if (isset($this->options['collation']) && ! \MongoDB\server_supports_feature($server, self::$wireVersionForCollation)) {
-            throw UnsupportedException::collationNotSupported();
-        }
-
-        if (isset($this->options['readConcern']) && ! \MongoDB\server_supports_feature($server, self::$wireVersionForReadConcern)) {
-            throw UnsupportedException::readConcernNotSupported();
-        }
-
-        $cursor = $server->executeReadCommand($this->databaseName, new Command($this->createCommandDocument()), $this->createOptions());
-        $result = current($cursor->toArray());
-
-        // Older server versions may return a float
-        if ( ! isset($result->n) || ! (is_integer($result->n) || is_float($result->n))) {
-            throw new UnexpectedValueException('count command did not return a numeric "n" value');
-        }
-
-        return (integer) $result->n;
+        return $this->count->execute($server);
     }
 
     public function getCommandDocument(Server $server)
     {
-        return $this->createCommandDocument();
+        return $this->count->getCommandDocument($server);
     }
 
     /**
-     * Create the count command document.
-     *
-     * @return array
+     * @return Count
      */
-    private function createCommandDocument()
+    private function createCount()
     {
-        $cmd = ['count' => $this->collectionName];
-
-        if (isset($this->options['maxTimeMS'])) {
-            $cmd['maxTimeMS'] = $this->options['maxTimeMS'];
-        }
-
-        return $cmd;
-    }
-
-    /**
-     * Create options for executing the command.
-     *
-     * @see http://php.net/manual/en/mongodb-driver-server.executereadcommand.php
-     * @return array
-     */
-    private function createOptions()
-    {
-        $options = [];
-
-        if (isset($this->options['readConcern'])) {
-            $options['readConcern'] = $this->options['readConcern'];
-        }
-
-        if (isset($this->options['readPreference'])) {
-            $options['readPreference'] = $this->options['readPreference'];
-        }
-
-        if (isset($this->options['session'])) {
-            $options['session'] = $this->options['session'];
-        }
-
-        return $options;
+        return new Count($this->databaseName, $this->collectionName, [], $this->options);
     }
 }
diff --git a/cache/stores/mongodb/MongoDB/Operation/Explain.php b/cache/stores/mongodb/MongoDB/Operation/Explain.php
index ceb0711e0b7..28a23390748 100644
--- a/cache/stores/mongodb/MongoDB/Operation/Explain.php
+++ b/cache/stores/mongodb/MongoDB/Operation/Explain.php
@@ -21,9 +21,12 @@ use MongoDB\Driver\Command;
 use MongoDB\Driver\ReadPreference;
 use MongoDB\Driver\Server;
 use MongoDB\Driver\Session;
-use MongoDB\Exception\UnsupportedException;
 use MongoDB\Exception\InvalidArgumentException;
-use MongoDB\Model\BSONDocument;
+use MongoDB\Exception\UnsupportedException;
+use function current;
+use function is_array;
+use function is_string;
+use function MongoDB\server_supports_feature;
 
 /**
  * Operation for the explain command.
@@ -38,11 +41,19 @@ class Explain implements Executable
     const VERBOSITY_EXEC_STATS = 'executionStats';
     const VERBOSITY_QUERY = 'queryPlanner';
 
+    /** @var integer */
     private static $wireVersionForDistinct = 4;
+
+    /** @var integer */
     private static $wireVersionForFindAndModify = 4;
 
+    /** @var string */
     private $databaseName;
+
+    /** @var Explainable */
     private $explainable;
+
+    /** @var array */
     private $options;
 
     /**
@@ -59,19 +70,19 @@ class Explain implements Executable
      *
      *  * verbosity (string): The mode in which the explain command will be run.
      *
-     * @param string $databaseName      Database name
+     * @param string      $databaseName Database name
      * @param Explainable $explainable  Operation to explain
-     * @param array  $options           Command options
+     * @param array       $options      Command options
      * @throws InvalidArgumentException for parameter/option parsing errors
      */
     public function __construct($databaseName, Explainable $explainable, array $options = [])
     {
         if (isset($options['readPreference']) && ! $options['readPreference'] instanceof ReadPreference) {
-            throw InvalidArgumentException::invalidType('"readPreference" option', $options['readPreference'], 'MongoDB\Driver\ReadPreference');
+            throw InvalidArgumentException::invalidType('"readPreference" option', $options['readPreference'], ReadPreference::class);
         }
 
         if (isset($options['session']) && ! $options['session'] instanceof Session) {
-            throw InvalidArgumentException::invalidType('"session" option', $options['session'], 'MongoDB\Driver\Session');
+            throw InvalidArgumentException::invalidType('"session" option', $options['session'], Session::class);
         }
 
         if (isset($options['typeMap']) && ! is_array($options['typeMap'])) {
@@ -89,11 +100,11 @@ class Explain implements Executable
 
     public function execute(Server $server)
     {
-        if ($this->explainable instanceof Distinct && ! \MongoDB\server_supports_feature($server, self::$wireVersionForDistinct)) {
+        if ($this->explainable instanceof Distinct && ! server_supports_feature($server, self::$wireVersionForDistinct)) {
             throw UnsupportedException::explainNotSupported();
         }
 
-        if ($this->isFindAndModify($this->explainable) && ! \MongoDB\server_supports_feature($server, self::$wireVersionForFindAndModify)) {
+        if ($this->isFindAndModify($this->explainable) && ! server_supports_feature($server, self::$wireVersionForFindAndModify)) {
             throw UnsupportedException::explainNotSupported();
         }
 
@@ -138,6 +149,7 @@ class Explain implements Executable
         if ($explainable instanceof FindAndModify || $explainable instanceof FindOneAndDelete || $explainable instanceof FindOneAndReplace || $explainable instanceof FindOneAndUpdate) {
             return true;
         }
+
         return false;
     }
 }
diff --git a/cache/stores/mongodb/MongoDB/Operation/Explainable.php b/cache/stores/mongodb/MongoDB/Operation/Explainable.php
index ee7cbd26344..ed4e99ab4e8 100644
--- a/cache/stores/mongodb/MongoDB/Operation/Explainable.php
+++ b/cache/stores/mongodb/MongoDB/Operation/Explainable.php
@@ -27,5 +27,5 @@ use MongoDB\Driver\Server;
  */
 interface Explainable extends Executable
 {
-    function getCommandDocument(Server $server);
+    public function getCommandDocument(Server $server);
 }
diff --git a/cache/stores/mongodb/MongoDB/Operation/Find.php b/cache/stores/mongodb/MongoDB/Operation/Find.php
index d7629d429d6..f6e11aba86a 100644
--- a/cache/stores/mongodb/MongoDB/Operation/Find.php
+++ b/cache/stores/mongodb/MongoDB/Operation/Find.php
@@ -18,15 +18,23 @@
 namespace MongoDB\Operation;
 
 use MongoDB\Driver\Cursor;
+use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
 use MongoDB\Driver\Query;
 use MongoDB\Driver\ReadConcern;
 use MongoDB\Driver\ReadPreference;
 use MongoDB\Driver\Server;
 use MongoDB\Driver\Session;
-use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
 use MongoDB\Exception\InvalidArgumentException;
 use MongoDB\Exception\UnsupportedException;
-use MongoDB\Model\BSONDocument;
+use function is_array;
+use function is_bool;
+use function is_integer;
+use function is_object;
+use function is_string;
+use function MongoDB\server_supports_feature;
+use function trigger_error;
+use const E_USER_DEPRECATED;
+
 /**
  * Operation for the find command.
  *
@@ -41,12 +49,22 @@ class Find implements Executable, Explainable
     const TAILABLE = 2;
     const TAILABLE_AWAIT = 3;
 
+    /** @var integer */
     private static $wireVersionForCollation = 5;
+
+    /** @var integer */
     private static $wireVersionForReadConcern = 4;
 
+    /** @var string */
     private $databaseName;
+
+    /** @var string */
     private $collectionName;
+
+    /** @var array|object */
     private $filter;
+
+    /** @var array */
     private $options;
 
     /**
@@ -147,7 +165,7 @@ class Find implements Executable, Explainable
      */
     public function __construct($databaseName, $collectionName, $filter, array $options = [])
     {
-        if ( ! is_array($filter) && ! is_object($filter)) {
+        if (! is_array($filter) && ! is_object($filter)) {
             throw InvalidArgumentException::invalidType('$filter', $filter, 'array or object');
         }
 
@@ -168,7 +186,7 @@ class Find implements Executable, Explainable
         }
 
         if (isset($options['cursorType'])) {
-            if ( ! is_integer($options['cursorType'])) {
+            if (! is_integer($options['cursorType'])) {
                 throw InvalidArgumentException::invalidType('"cursorType" option', $options['cursorType'], 'integer');
             }
 
@@ -224,11 +242,11 @@ class Find implements Executable, Explainable
         }
 
         if (isset($options['readConcern']) && ! $options['readConcern'] instanceof ReadConcern) {
-            throw InvalidArgumentException::invalidType('"readConcern" option', $options['readConcern'], 'MongoDB\Driver\ReadConcern');
+            throw InvalidArgumentException::invalidType('"readConcern" option', $options['readConcern'], ReadConcern::class);
         }
 
         if (isset($options['readPreference']) && ! $options['readPreference'] instanceof ReadPreference) {
-            throw InvalidArgumentException::invalidType('"readPreference" option', $options['readPreference'], 'MongoDB\Driver\ReadPreference');
+            throw InvalidArgumentException::invalidType('"readPreference" option', $options['readPreference'], ReadPreference::class);
         }
 
         if (isset($options['returnKey']) && ! is_bool($options['returnKey'])) {
@@ -236,7 +254,7 @@ class Find implements Executable, Explainable
         }
 
         if (isset($options['session']) && ! $options['session'] instanceof Session) {
-            throw InvalidArgumentException::invalidType('"session" option', $options['session'], 'MongoDB\Driver\Session');
+            throw InvalidArgumentException::invalidType('"session" option', $options['session'], Session::class);
         }
 
         if (isset($options['showRecordId']) && ! is_bool($options['showRecordId'])) {
@@ -288,14 +306,19 @@ class Find implements Executable, Explainable
      */
     public function execute(Server $server)
     {
-        if (isset($this->options['collation']) && ! \MongoDB\server_supports_feature($server, self::$wireVersionForCollation)) {
+        if (isset($this->options['collation']) && ! server_supports_feature($server, self::$wireVersionForCollation)) {
             throw UnsupportedException::collationNotSupported();
         }
 
-        if (isset($this->options['readConcern']) && ! \MongoDB\server_supports_feature($server, self::$wireVersionForReadConcern)) {
+        if (isset($this->options['readConcern']) && ! server_supports_feature($server, self::$wireVersionForReadConcern)) {
             throw UnsupportedException::readConcernNotSupported();
         }
 
+        $inTransaction = isset($this->options['session']) && $this->options['session']->isInTransaction();
+        if ($inTransaction && isset($this->options['readConcern'])) {
+            throw UnsupportedException::readConcernNotSupportedInTransaction();
+        }
+
         $cursor = $server->executeQuery($this->databaseName . '.' . $this->collectionName, new Query($this->filter, $this->createQueryOptions()), $this->createExecuteOptions());
 
         if (isset($this->options['typeMap'])) {
@@ -341,7 +364,7 @@ class Find implements Executable, Explainable
         ];
 
         foreach ($modifierFallback as $modifier) {
-            if ( ! isset($options[$modifier[0]]) && isset($options['modifiers'][$modifier[1]])) {
+            if (! isset($options[$modifier[0]]) && isset($options['modifiers'][$modifier[1]])) {
                 $options[$modifier[0]] = $options['modifiers'][$modifier[1]];
             }
         }
@@ -407,7 +430,7 @@ class Find implements Executable, Explainable
 
         $modifiers = empty($this->options['modifiers']) ? [] : (array) $this->options['modifiers'];
 
-        if ( ! empty($modifiers)) {
+        if (! empty($modifiers)) {
             $options['modifiers'] = $modifiers;
         }
 
diff --git a/cache/stores/mongodb/MongoDB/Operation/FindAndModify.php b/cache/stores/mongodb/MongoDB/Operation/FindAndModify.php
index b00bd1e58c7..acce4366b03 100644
--- a/cache/stores/mongodb/MongoDB/Operation/FindAndModify.php
+++ b/cache/stores/mongodb/MongoDB/Operation/FindAndModify.php
@@ -18,13 +18,21 @@
 namespace MongoDB\Operation;
 
 use MongoDB\Driver\Command;
+use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
 use MongoDB\Driver\Server;
 use MongoDB\Driver\Session;
 use MongoDB\Driver\WriteConcern;
-use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
 use MongoDB\Exception\InvalidArgumentException;
 use MongoDB\Exception\UnexpectedValueException;
 use MongoDB\Exception\UnsupportedException;
+use function current;
+use function is_array;
+use function is_bool;
+use function is_integer;
+use function is_object;
+use function MongoDB\create_field_path_type_map;
+use function MongoDB\is_pipeline;
+use function MongoDB\server_supports_feature;
 
 /**
  * Operation for the findAndModify command.
@@ -37,13 +45,25 @@ use MongoDB\Exception\UnsupportedException;
  */
 class FindAndModify implements Executable, Explainable
 {
+    /** @var integer */
     private static $wireVersionForArrayFilters = 6;
+
+    /** @var integer */
     private static $wireVersionForCollation = 5;
+
+    /** @var integer */
     private static $wireVersionForDocumentLevelValidation = 4;
+
+    /** @var integer */
     private static $wireVersionForWriteConcern = 4;
 
+    /** @var string */
     private $databaseName;
+
+    /** @var string */
     private $collectionName;
+
+    /** @var array */
     private $options;
 
     /**
@@ -137,7 +157,7 @@ class FindAndModify implements Executable, Explainable
             throw InvalidArgumentException::invalidType('"maxTimeMS" option', $options['maxTimeMS'], 'integer');
         }
 
-        if ( ! is_bool($options['new'])) {
+        if (! is_bool($options['new'])) {
             throw InvalidArgumentException::invalidType('"new" option', $options['new'], 'boolean');
         }
 
@@ -145,12 +165,12 @@ class FindAndModify implements Executable, Explainable
             throw InvalidArgumentException::invalidType('"query" option', $options['query'], 'array or object');
         }
 
-        if ( ! is_bool($options['remove'])) {
+        if (! is_bool($options['remove'])) {
             throw InvalidArgumentException::invalidType('"remove" option', $options['remove'], 'boolean');
         }
 
         if (isset($options['session']) && ! $options['session'] instanceof Session) {
-            throw InvalidArgumentException::invalidType('"session" option', $options['session'], 'MongoDB\Driver\Session');
+            throw InvalidArgumentException::invalidType('"session" option', $options['session'], Session::class);
         }
 
         if (isset($options['sort']) && ! is_array($options['sort']) && ! is_object($options['sort'])) {
@@ -166,14 +186,14 @@ class FindAndModify implements Executable, Explainable
         }
 
         if (isset($options['writeConcern']) && ! $options['writeConcern'] instanceof WriteConcern) {
-            throw InvalidArgumentException::invalidType('"writeConcern" option', $options['writeConcern'], 'MongoDB\Driver\WriteConcern');
+            throw InvalidArgumentException::invalidType('"writeConcern" option', $options['writeConcern'], WriteConcern::class);
         }
 
-        if ( ! is_bool($options['upsert'])) {
+        if (! is_bool($options['upsert'])) {
             throw InvalidArgumentException::invalidType('"upsert" option', $options['upsert'], 'boolean');
         }
 
-        if ( ! (isset($options['update']) xor $options['remove'])) {
+        if (! (isset($options['update']) xor $options['remove'])) {
             throw new InvalidArgumentException('The "remove" option must be true or an "update" document must be specified, but not both');
         }
 
@@ -198,34 +218,32 @@ class FindAndModify implements Executable, Explainable
      */
     public function execute(Server $server)
     {
-        if (isset($this->options['arrayFilters']) && ! \MongoDB\server_supports_feature($server, self::$wireVersionForArrayFilters)) {
+        if (isset($this->options['arrayFilters']) && ! server_supports_feature($server, self::$wireVersionForArrayFilters)) {
             throw UnsupportedException::arrayFiltersNotSupported();
         }
 
-        if (isset($this->options['collation']) && ! \MongoDB\server_supports_feature($server, self::$wireVersionForCollation)) {
+        if (isset($this->options['collation']) && ! server_supports_feature($server, self::$wireVersionForCollation)) {
             throw UnsupportedException::collationNotSupported();
         }
 
-        if (isset($this->options['writeConcern']) && ! \MongoDB\server_supports_feature($server, self::$wireVersionForWriteConcern)) {
+        if (isset($this->options['writeConcern']) && ! server_supports_feature($server, self::$wireVersionForWriteConcern)) {
             throw UnsupportedException::writeConcernNotSupported();
         }
 
+        $inTransaction = isset($this->options['session']) && $this->options['session']->isInTransaction();
+        if ($inTransaction && isset($this->options['writeConcern'])) {
+            throw UnsupportedException::writeConcernNotSupportedInTransaction();
+        }
+
         $cursor = $server->executeWriteCommand($this->databaseName, new Command($this->createCommandDocument($server)), $this->createOptions());
-        $result = current($cursor->toArray());
-
-        if ( ! isset($result->value)) {
-            return null;
-        }
-
-        if ( ! is_object($result->value)) {
-            throw new UnexpectedValueException('findAndModify command did not return a "value" document');
-        }
 
         if (isset($this->options['typeMap'])) {
-            return \MongoDB\apply_type_map_to_document($result->value, $this->options['typeMap']);
+            $cursor->setTypeMap(create_field_path_type_map($this->options['typeMap'], 'value'));
         }
 
-        return $result->value;
+        $result = current($cursor->toArray());
+
+        return isset($result->value) ? $result->value : null;
     }
 
     public function getCommandDocument(Server $server)
@@ -236,6 +254,7 @@ class FindAndModify implements Executable, Explainable
     /**
      * Create the findAndModify command document.
      *
+     * @param Server $server
      * @return array
      */
     private function createCommandDocument(Server $server)
@@ -249,12 +268,18 @@ class FindAndModify implements Executable, Explainable
             $cmd['upsert'] = $this->options['upsert'];
         }
 
-        foreach (['collation', 'fields', 'query', 'sort', 'update'] as $option) {
+        foreach (['collation', 'fields', 'query', 'sort'] as $option) {
             if (isset($this->options[$option])) {
                 $cmd[$option] = (object) $this->options[$option];
             }
         }
 
+        if (isset($this->options['update'])) {
+            $cmd['update'] = is_pipeline($this->options['update'])
+                ? $this->options['update']
+                : (object) $this->options['update'];
+        }
+
         if (isset($this->options['arrayFilters'])) {
             $cmd['arrayFilters'] = $this->options['arrayFilters'];
         }
@@ -263,7 +288,9 @@ class FindAndModify implements Executable, Explainable
             $cmd['maxTimeMS'] = $this->options['maxTimeMS'];
         }
 
-        if (isset($this->options['bypassDocumentValidation']) && \MongoDB\server_supports_feature($server, self::$wireVersionForDocumentLevelValidation)) {
+        if (! empty($this->options['bypassDocumentValidation']) &&
+            server_supports_feature($server, self::$wireVersionForDocumentLevelValidation)
+        ) {
             $cmd['bypassDocumentValidation'] = $this->options['bypassDocumentValidation'];
         }
 
diff --git a/cache/stores/mongodb/MongoDB/Operation/FindOne.php b/cache/stores/mongodb/MongoDB/Operation/FindOne.php
index a5c682057e3..48f601ce6fa 100644
--- a/cache/stores/mongodb/MongoDB/Operation/FindOne.php
+++ b/cache/stores/mongodb/MongoDB/Operation/FindOne.php
@@ -17,10 +17,11 @@
 
 namespace MongoDB\Operation;
 
-use MongoDB\Driver\Server;
 use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
+use MongoDB\Driver\Server;
 use MongoDB\Exception\InvalidArgumentException;
 use MongoDB\Exception\UnsupportedException;
+use function current;
 
 /**
  * Operation for finding a single document with the find command.
@@ -32,6 +33,7 @@ use MongoDB\Exception\UnsupportedException;
  */
 class FindOne implements Executable, Explainable
 {
+    /** @var Find */
     private $find;
 
     /**
@@ -126,7 +128,7 @@ class FindOne implements Executable, Explainable
         $cursor = $this->find->execute($server);
         $document = current($cursor->toArray());
 
-        return ($document === false) ? null : $document;
+        return $document === false ? null : $document;
     }
 
     public function getCommandDocument(Server $server)
diff --git a/cache/stores/mongodb/MongoDB/Operation/FindOneAndDelete.php b/cache/stores/mongodb/MongoDB/Operation/FindOneAndDelete.php
index 1a650f4c0db..489ca3e95f0 100644
--- a/cache/stores/mongodb/MongoDB/Operation/FindOneAndDelete.php
+++ b/cache/stores/mongodb/MongoDB/Operation/FindOneAndDelete.php
@@ -17,10 +17,12 @@
 
 namespace MongoDB\Operation;
 
-use MongoDB\Driver\Server;
 use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
+use MongoDB\Driver\Server;
 use MongoDB\Exception\InvalidArgumentException;
 use MongoDB\Exception\UnsupportedException;
+use function is_array;
+use function is_object;
 
 /**
  * Operation for deleting a document with the findAndModify command.
@@ -31,6 +33,7 @@ use MongoDB\Exception\UnsupportedException;
  */
 class FindOneAndDelete implements Executable, Explainable
 {
+    /** @var FindAndModify */
     private $findAndModify;
 
     /**
@@ -71,7 +74,7 @@ class FindOneAndDelete implements Executable, Explainable
      */
     public function __construct($databaseName, $collectionName, $filter, array $options = [])
     {
-        if ( ! is_array($filter) && ! is_object($filter)) {
+        if (! is_array($filter) && ! is_object($filter)) {
             throw InvalidArgumentException::invalidType('$filter', $filter, 'array or object');
         }
 
diff --git a/cache/stores/mongodb/MongoDB/Operation/FindOneAndReplace.php b/cache/stores/mongodb/MongoDB/Operation/FindOneAndReplace.php
index c1b4892711e..43721c37257 100644
--- a/cache/stores/mongodb/MongoDB/Operation/FindOneAndReplace.php
+++ b/cache/stores/mongodb/MongoDB/Operation/FindOneAndReplace.php
@@ -17,10 +17,14 @@
 
 namespace MongoDB\Operation;
 
-use MongoDB\Driver\Server;
 use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
+use MongoDB\Driver\Server;
 use MongoDB\Exception\InvalidArgumentException;
 use MongoDB\Exception\UnsupportedException;
+use function is_array;
+use function is_integer;
+use function is_object;
+use function MongoDB\is_first_key_operator;
 
 /**
  * Operation for replacing a document with the findAndModify command.
@@ -34,6 +38,7 @@ class FindOneAndReplace implements Executable, Explainable
     const RETURN_DOCUMENT_BEFORE = 1;
     const RETURN_DOCUMENT_AFTER = 2;
 
+    /** @var FindAndModify */
     private $findAndModify;
 
     /**
@@ -90,15 +95,15 @@ class FindOneAndReplace implements Executable, Explainable
      */
     public function __construct($databaseName, $collectionName, $filter, $replacement, array $options = [])
     {
-        if ( ! is_array($filter) && ! is_object($filter)) {
+        if (! is_array($filter) && ! is_object($filter)) {
             throw InvalidArgumentException::invalidType('$filter', $filter, 'array or object');
         }
 
-        if ( ! is_array($replacement) && ! is_object($replacement)) {
+        if (! is_array($replacement) && ! is_object($replacement)) {
             throw InvalidArgumentException::invalidType('$replacement', $replacement, 'array or object');
         }
 
-        if (\MongoDB\is_first_key_operator($replacement)) {
+        if (is_first_key_operator($replacement)) {
             throw new InvalidArgumentException('First key in $replacement argument is an update operator');
         }
 
@@ -111,7 +116,7 @@ class FindOneAndReplace implements Executable, Explainable
             throw InvalidArgumentException::invalidType('"projection" option', $options['projection'], 'array or object');
         }
 
-        if ( ! is_integer($options['returnDocument'])) {
+        if (! is_integer($options['returnDocument'])) {
             throw InvalidArgumentException::invalidType('"returnDocument" option', $options['returnDocument'], 'integer');
         }
 
diff --git a/cache/stores/mongodb/MongoDB/Operation/FindOneAndUpdate.php b/cache/stores/mongodb/MongoDB/Operation/FindOneAndUpdate.php
index c9d15cc214d..ed38e0c2772 100644
--- a/cache/stores/mongodb/MongoDB/Operation/FindOneAndUpdate.php
+++ b/cache/stores/mongodb/MongoDB/Operation/FindOneAndUpdate.php
@@ -17,10 +17,15 @@
 
 namespace MongoDB\Operation;
 
-use MongoDB\Driver\Server;
 use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
+use MongoDB\Driver\Server;
 use MongoDB\Exception\InvalidArgumentException;
 use MongoDB\Exception\UnsupportedException;
+use function is_array;
+use function is_integer;
+use function is_object;
+use function MongoDB\is_first_key_operator;
+use function MongoDB\is_pipeline;
 
 /**
  * Operation for updating a document with the findAndModify command.
@@ -34,6 +39,7 @@ class FindOneAndUpdate implements Executable, Explainable
     const RETURN_DOCUMENT_BEFORE = 1;
     const RETURN_DOCUMENT_AFTER = 2;
 
+    /** @var FindAndModify */
     private $findAndModify;
 
     /**
@@ -93,16 +99,16 @@ class FindOneAndUpdate implements Executable, Explainable
      */
     public function __construct($databaseName, $collectionName, $filter, $update, array $options = [])
     {
-        if ( ! is_array($filter) && ! is_object($filter)) {
+        if (! is_array($filter) && ! is_object($filter)) {
             throw InvalidArgumentException::invalidType('$filter', $filter, 'array or object');
         }
 
-        if ( ! is_array($update) && ! is_object($update)) {
+        if (! is_array($update) && ! is_object($update)) {
             throw InvalidArgumentException::invalidType('$update', $update, 'array or object');
         }
 
-        if ( ! \MongoDB\is_first_key_operator($update)) {
-            throw new InvalidArgumentException('First key in $update argument is not an update operator');
+        if (! is_first_key_operator($update) && ! is_pipeline($update)) {
+            throw new InvalidArgumentException('Expected an update document with operator as first key or a pipeline');
         }
 
         $options += [
@@ -114,7 +120,7 @@ class FindOneAndUpdate implements Executable, Explainable
             throw InvalidArgumentException::invalidType('"projection" option', $options['projection'], 'array or object');
         }
 
-        if ( ! is_integer($options['returnDocument'])) {
+        if (! is_integer($options['returnDocument'])) {
             throw InvalidArgumentException::invalidType('"returnDocument" option', $options['returnDocument'], 'integer');
         }
 
diff --git a/cache/stores/mongodb/MongoDB/Operation/InsertMany.php b/cache/stores/mongodb/MongoDB/Operation/InsertMany.php
index afa9427c170..768907592b6 100644
--- a/cache/stores/mongodb/MongoDB/Operation/InsertMany.php
+++ b/cache/stores/mongodb/MongoDB/Operation/InsertMany.php
@@ -17,13 +17,19 @@
 
 namespace MongoDB\Operation;
 
-use MongoDB\InsertManyResult;
 use MongoDB\Driver\BulkWrite as Bulk;
+use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
 use MongoDB\Driver\Server;
 use MongoDB\Driver\Session;
 use MongoDB\Driver\WriteConcern;
-use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
 use MongoDB\Exception\InvalidArgumentException;
+use MongoDB\Exception\UnsupportedException;
+use MongoDB\InsertManyResult;
+use function is_array;
+use function is_bool;
+use function is_object;
+use function MongoDB\server_supports_feature;
+use function sprintf;
 
 /**
  * Operation for inserting multiple documents with the insert command.
@@ -34,11 +40,19 @@ use MongoDB\Exception\InvalidArgumentException;
  */
 class InsertMany implements Executable
 {
+    /** @var integer */
     private static $wireVersionForDocumentLevelValidation = 4;
 
+    /** @var string */
     private $databaseName;
+
+    /** @var string */
     private $collectionName;
+
+    /** @var object[]|array[] */
     private $documents;
+
+    /** @var array */
     private $options;
 
     /**
@@ -81,7 +95,7 @@ class InsertMany implements Executable
                 throw new InvalidArgumentException(sprintf('$documents is not a list (unexpected index: "%s")', $i));
             }
 
-            if ( ! is_array($document) && ! is_object($document)) {
+            if (! is_array($document) && ! is_object($document)) {
                 throw InvalidArgumentException::invalidType(sprintf('$documents[%d]', $i), $document, 'array or object');
             }
 
@@ -94,16 +108,16 @@ class InsertMany implements Executable
             throw InvalidArgumentException::invalidType('"bypassDocumentValidation" option', $options['bypassDocumentValidation'], 'boolean');
         }
 
-        if ( ! is_bool($options['ordered'])) {
+        if (! is_bool($options['ordered'])) {
             throw InvalidArgumentException::invalidType('"ordered" option', $options['ordered'], 'boolean');
         }
 
         if (isset($options['session']) && ! $options['session'] instanceof Session) {
-            throw InvalidArgumentException::invalidType('"session" option', $options['session'], 'MongoDB\Driver\Session');
+            throw InvalidArgumentException::invalidType('"session" option', $options['session'], Session::class);
         }
 
         if (isset($options['writeConcern']) && ! $options['writeConcern'] instanceof WriteConcern) {
-            throw InvalidArgumentException::invalidType('"writeConcern" option', $options['writeConcern'], 'MongoDB\Driver\WriteConcern');
+            throw InvalidArgumentException::invalidType('"writeConcern" option', $options['writeConcern'], WriteConcern::class);
         }
 
         if (isset($options['writeConcern']) && $options['writeConcern']->isDefault()) {
@@ -126,9 +140,16 @@ class InsertMany implements Executable
      */
     public function execute(Server $server)
     {
+        $inTransaction = isset($this->options['session']) && $this->options['session']->isInTransaction();
+        if ($inTransaction && isset($this->options['writeConcern'])) {
+            throw UnsupportedException::writeConcernNotSupportedInTransaction();
+        }
+
         $options = ['ordered' => $this->options['ordered']];
 
-        if (isset($this->options['bypassDocumentValidation']) && \MongoDB\server_supports_feature($server, self::$wireVersionForDocumentLevelValidation)) {
+        if (! empty($this->options['bypassDocumentValidation']) &&
+            server_supports_feature($server, self::$wireVersionForDocumentLevelValidation)
+        ) {
             $options['bypassDocumentValidation'] = $this->options['bypassDocumentValidation'];
         }
 
diff --git a/cache/stores/mongodb/MongoDB/Operation/InsertOne.php b/cache/stores/mongodb/MongoDB/Operation/InsertOne.php
index 209d5c2fae9..84d6a4aa17c 100644
--- a/cache/stores/mongodb/MongoDB/Operation/InsertOne.php
+++ b/cache/stores/mongodb/MongoDB/Operation/InsertOne.php
@@ -17,13 +17,18 @@
 
 namespace MongoDB\Operation;
 
-use MongoDB\InsertOneResult;
 use MongoDB\Driver\BulkWrite as Bulk;
+use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
 use MongoDB\Driver\Server;
 use MongoDB\Driver\Session;
 use MongoDB\Driver\WriteConcern;
-use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
 use MongoDB\Exception\InvalidArgumentException;
+use MongoDB\Exception\UnsupportedException;
+use MongoDB\InsertOneResult;
+use function is_array;
+use function is_bool;
+use function is_object;
+use function MongoDB\server_supports_feature;
 
 /**
  * Operation for inserting a single document with the insert command.
@@ -34,11 +39,19 @@ use MongoDB\Exception\InvalidArgumentException;
  */
 class InsertOne implements Executable
 {
+    /** @var integer */
     private static $wireVersionForDocumentLevelValidation = 4;
 
+    /** @var string */
     private $databaseName;
+
+    /** @var string */
     private $collectionName;
+
+    /** @var array|object */
     private $document;
+
+    /** @var array */
     private $options;
 
     /**
@@ -66,7 +79,7 @@ class InsertOne implements Executable
      */
     public function __construct($databaseName, $collectionName, $document, array $options = [])
     {
-        if ( ! is_array($document) && ! is_object($document)) {
+        if (! is_array($document) && ! is_object($document)) {
             throw InvalidArgumentException::invalidType('$document', $document, 'array or object');
         }
 
@@ -75,11 +88,11 @@ class InsertOne implements Executable
         }
 
         if (isset($options['session']) && ! $options['session'] instanceof Session) {
-            throw InvalidArgumentException::invalidType('"session" option', $options['session'], 'MongoDB\Driver\Session');
+            throw InvalidArgumentException::invalidType('"session" option', $options['session'], Session::class);
         }
 
         if (isset($options['writeConcern']) && ! $options['writeConcern'] instanceof WriteConcern) {
-            throw InvalidArgumentException::invalidType('"writeConcern" option', $options['writeConcern'], 'MongoDB\Driver\WriteConcern');
+            throw InvalidArgumentException::invalidType('"writeConcern" option', $options['writeConcern'], WriteConcern::class);
         }
 
         if (isset($options['writeConcern']) && $options['writeConcern']->isDefault()) {
@@ -104,7 +117,14 @@ class InsertOne implements Executable
     {
         $options = [];
 
-        if (isset($this->options['bypassDocumentValidation']) && \MongoDB\server_supports_feature($server, self::$wireVersionForDocumentLevelValidation)) {
+        $inTransaction = isset($this->options['session']) && $this->options['session']->isInTransaction();
+        if (isset($this->options['writeConcern']) && $inTransaction) {
+            throw UnsupportedException::writeConcernNotSupportedInTransaction();
+        }
+
+        if (! empty($this->options['bypassDocumentValidation']) &&
+            server_supports_feature($server, self::$wireVersionForDocumentLevelValidation)
+        ) {
             $options['bypassDocumentValidation'] = $this->options['bypassDocumentValidation'];
         }
 
diff --git a/cache/stores/mongodb/MongoDB/Operation/ListCollections.php b/cache/stores/mongodb/MongoDB/Operation/ListCollections.php
index 41988bc34a4..1d1fdf5612b 100644
--- a/cache/stores/mongodb/MongoDB/Operation/ListCollections.php
+++ b/cache/stores/mongodb/MongoDB/Operation/ListCollections.php
@@ -18,15 +18,16 @@
 namespace MongoDB\Operation;
 
 use MongoDB\Driver\Command;
-use MongoDB\Driver\Query;
+use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
 use MongoDB\Driver\Server;
 use MongoDB\Driver\Session;
-use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
 use MongoDB\Exception\InvalidArgumentException;
 use MongoDB\Model\CachingIterator;
 use MongoDB\Model\CollectionInfoCommandIterator;
 use MongoDB\Model\CollectionInfoIterator;
-use MongoDB\Model\CollectionInfoLegacyIterator;
+use function is_array;
+use function is_integer;
+use function is_object;
 
 /**
  * Operation for the listCollections command.
@@ -37,7 +38,10 @@ use MongoDB\Model\CollectionInfoLegacyIterator;
  */
 class ListCollections implements Executable
 {
+    /** @var string */
     private $databaseName;
+
+    /** @var array */
     private $options;
 
     /**
@@ -69,7 +73,7 @@ class ListCollections implements Executable
         }
 
         if (isset($options['session']) && ! $options['session'] instanceof Session) {
-            throw InvalidArgumentException::invalidType('"session" option', $options['session'], 'MongoDB\Driver\Session');
+            throw InvalidArgumentException::invalidType('"session" option', $options['session'], Session::class);
         }
 
         $this->databaseName = (string) $databaseName;
@@ -121,7 +125,7 @@ class ListCollections implements Executable
     {
         $cmd = ['listCollections' => 1];
 
-        if ( ! empty($this->options['filter'])) {
+        if (! empty($this->options['filter'])) {
             $cmd['filter'] = (object) $this->options['filter'];
         }
 
@@ -129,7 +133,7 @@ class ListCollections implements Executable
             $cmd['maxTimeMS'] = $this->options['maxTimeMS'];
         }
 
-        $cursor = $server->executeCommand($this->databaseName, new Command($cmd), $this->createOptions());
+        $cursor = $server->executeReadCommand($this->databaseName, new Command($cmd), $this->createOptions());
         $cursor->setTypeMap(['root' => 'array', 'document' => 'array']);
 
         return new CollectionInfoCommandIterator(new CachingIterator($cursor));
diff --git a/cache/stores/mongodb/MongoDB/Operation/ListDatabases.php b/cache/stores/mongodb/MongoDB/Operation/ListDatabases.php
index fca38fb133d..c405236917b 100644
--- a/cache/stores/mongodb/MongoDB/Operation/ListDatabases.php
+++ b/cache/stores/mongodb/MongoDB/Operation/ListDatabases.php
@@ -18,13 +18,17 @@
 namespace MongoDB\Operation;
 
 use MongoDB\Driver\Command;
+use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
 use MongoDB\Driver\Server;
 use MongoDB\Driver\Session;
-use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
 use MongoDB\Exception\InvalidArgumentException;
 use MongoDB\Exception\UnexpectedValueException;
 use MongoDB\Model\DatabaseInfoIterator;
 use MongoDB\Model\DatabaseInfoLegacyIterator;
+use function current;
+use function is_array;
+use function is_integer;
+use function is_object;
 
 /**
  * Operation for the ListDatabases command.
@@ -35,6 +39,7 @@ use MongoDB\Model\DatabaseInfoLegacyIterator;
  */
 class ListDatabases implements Executable
 {
+    /** @var array */
     private $options;
 
     /**
@@ -67,7 +72,7 @@ class ListDatabases implements Executable
         }
 
         if (isset($options['session']) && ! $options['session'] instanceof Session) {
-            throw InvalidArgumentException::invalidType('"session" option', $options['session'], 'MongoDB\Driver\Session');
+            throw InvalidArgumentException::invalidType('"session" option', $options['session'], Session::class);
         }
 
         $this->options = $options;
@@ -86,7 +91,7 @@ class ListDatabases implements Executable
     {
         $cmd = ['listDatabases' => 1];
 
-        if ( ! empty($this->options['filter'])) {
+        if (! empty($this->options['filter'])) {
             $cmd['filter'] = (object) $this->options['filter'];
         }
 
@@ -94,11 +99,11 @@ class ListDatabases implements Executable
             $cmd['maxTimeMS'] = $this->options['maxTimeMS'];
         }
 
-        $cursor = $server->executeCommand('admin', new Command($cmd), $this->createOptions());
+        $cursor = $server->executeReadCommand('admin', new Command($cmd), $this->createOptions());
         $cursor->setTypeMap(['root' => 'array', 'document' => 'array']);
         $result = current($cursor->toArray());
 
-        if ( ! isset($result['databases']) || ! is_array($result['databases'])) {
+        if (! isset($result['databases']) || ! is_array($result['databases'])) {
             throw new UnexpectedValueException('listDatabases command did not return a "databases" array');
         }
 
diff --git a/cache/stores/mongodb/MongoDB/Operation/ListIndexes.php b/cache/stores/mongodb/MongoDB/Operation/ListIndexes.php
index a0ba544edaa..96aa5b95d11 100644
--- a/cache/stores/mongodb/MongoDB/Operation/ListIndexes.php
+++ b/cache/stores/mongodb/MongoDB/Operation/ListIndexes.php
@@ -17,16 +17,16 @@
 
 namespace MongoDB\Operation;
 
+use EmptyIterator;
 use MongoDB\Driver\Command;
-use MongoDB\Driver\Query;
+use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
 use MongoDB\Driver\Server;
 use MongoDB\Driver\Session;
-use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
 use MongoDB\Exception\InvalidArgumentException;
 use MongoDB\Model\CachingIterator;
 use MongoDB\Model\IndexInfoIterator;
 use MongoDB\Model\IndexInfoIteratorIterator;
-use EmptyIterator;
+use function is_integer;
 
 /**
  * Operation for the listIndexes command.
@@ -37,11 +37,19 @@ use EmptyIterator;
  */
 class ListIndexes implements Executable
 {
+    /** @var integer */
     private static $errorCodeDatabaseNotFound = 60;
+
+    /** @var integer */
     private static $errorCodeNamespaceNotFound = 26;
 
+    /** @var string */
     private $databaseName;
+
+    /** @var string */
     private $collectionName;
+
+    /** @var array */
     private $options;
 
     /**
@@ -68,7 +76,7 @@ class ListIndexes implements Executable
         }
 
         if (isset($options['session']) && ! $options['session'] instanceof Session) {
-            throw InvalidArgumentException::invalidType('"session" option', $options['session'], 'MongoDB\Driver\Session');
+            throw InvalidArgumentException::invalidType('"session" option', $options['session'], Session::class);
         }
 
         $this->databaseName = (string) $databaseName;
@@ -126,14 +134,14 @@ class ListIndexes implements Executable
         }
 
         try {
-            $cursor = $server->executeCommand($this->databaseName, new Command($cmd), $this->createOptions());
+            $cursor = $server->executeReadCommand($this->databaseName, new Command($cmd), $this->createOptions());
         } catch (DriverRuntimeException $e) {
             /* The server may return an error if the collection does not exist.
              * Check for possible error codes (see: SERVER-20463) and return an
              * empty iterator instead of throwing.
              */
             if ($e->getCode() === self::$errorCodeNamespaceNotFound || $e->getCode() === self::$errorCodeDatabaseNotFound) {
-                return new IndexInfoIteratorIterator(new EmptyIterator);
+                return new IndexInfoIteratorIterator(new EmptyIterator());
             }
 
             throw $e;
diff --git a/cache/stores/mongodb/MongoDB/Operation/MapReduce.php b/cache/stores/mongodb/MongoDB/Operation/MapReduce.php
index 1e9b4b9c6ab..22c357dc6ea 100644
--- a/cache/stores/mongodb/MongoDB/Operation/MapReduce.php
+++ b/cache/stores/mongodb/MongoDB/Operation/MapReduce.php
@@ -17,21 +17,29 @@
 
 namespace MongoDB\Operation;
 
+use ArrayIterator;
 use MongoDB\BSON\JavascriptInterface;
 use MongoDB\Driver\Command;
+use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
 use MongoDB\Driver\ReadConcern;
 use MongoDB\Driver\ReadPreference;
 use MongoDB\Driver\Server;
 use MongoDB\Driver\Session;
 use MongoDB\Driver\WriteConcern;
-use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
 use MongoDB\Exception\InvalidArgumentException;
 use MongoDB\Exception\UnexpectedValueException;
 use MongoDB\Exception\UnsupportedException;
-use MongoDB\Model\TypeMapArrayIterator;
 use MongoDB\MapReduceResult;
-use ArrayIterator;
 use stdClass;
+use function current;
+use function is_array;
+use function is_bool;
+use function is_integer;
+use function is_object;
+use function is_string;
+use function MongoDB\create_field_path_type_map;
+use function MongoDB\is_mapreduce_output_inline;
+use function MongoDB\server_supports_feature;
 
 /**
  * Operation for the mapReduce command.
@@ -42,16 +50,34 @@ use stdClass;
  */
 class MapReduce implements Executable
 {
+    /** @var integer */
     private static $wireVersionForCollation = 5;
+
+    /** @var integer */
     private static $wireVersionForDocumentLevelValidation = 4;
+
+    /** @var integer */
     private static $wireVersionForReadConcern = 4;
+
+    /** @var integer */
     private static $wireVersionForWriteConcern = 4;
 
+    /** @var string */
     private $databaseName;
+
+    /** @var string */
     private $collectionName;
+
+    /** @var JavascriptInterface */
     private $map;
+
+    /** @var JavascriptInterface */
     private $reduce;
+
+    /** @var array|object|string */
     private $out;
+
+    /** @var array */
     private $options;
 
     /**
@@ -144,7 +170,7 @@ class MapReduce implements Executable
      */
     public function __construct($databaseName, $collectionName, JavascriptInterface $map, JavascriptInterface $reduce, $out, array $options = [])
     {
-        if ( ! is_string($out) && ! is_array($out) && ! is_object($out)) {
+        if (! is_string($out) && ! is_array($out) && ! is_object($out)) {
             throw InvalidArgumentException::invalidType('$out', $out, 'string or array or object');
         }
 
@@ -157,7 +183,7 @@ class MapReduce implements Executable
         }
 
         if (isset($options['finalize']) && ! $options['finalize'] instanceof JavascriptInterface) {
-            throw InvalidArgumentException::invalidType('"finalize" option', $options['finalize'], 'MongoDB\Driver\Javascript');
+            throw InvalidArgumentException::invalidType('"finalize" option', $options['finalize'], JavascriptInterface::class);
         }
 
         if (isset($options['jsMode']) && ! is_bool($options['jsMode'])) {
@@ -177,11 +203,11 @@ class MapReduce implements Executable
         }
 
         if (isset($options['readConcern']) && ! $options['readConcern'] instanceof ReadConcern) {
-            throw InvalidArgumentException::invalidType('"readConcern" option', $options['readConcern'], 'MongoDB\Driver\ReadConcern');
+            throw InvalidArgumentException::invalidType('"readConcern" option', $options['readConcern'], ReadConcern::class);
         }
 
         if (isset($options['readPreference']) && ! $options['readPreference'] instanceof ReadPreference) {
-            throw InvalidArgumentException::invalidType('"readPreference" option', $options['readPreference'], 'MongoDB\Driver\ReadPreference');
+            throw InvalidArgumentException::invalidType('"readPreference" option', $options['readPreference'], ReadPreference::class);
         }
 
         if (isset($options['scope']) && ! is_array($options['scope']) && ! is_object($options['scope'])) {
@@ -189,7 +215,7 @@ class MapReduce implements Executable
         }
 
         if (isset($options['session']) && ! $options['session'] instanceof Session) {
-            throw InvalidArgumentException::invalidType('"session" option', $options['session'], 'MongoDB\Driver\Session');
+            throw InvalidArgumentException::invalidType('"session" option', $options['session'], Session::class);
         }
 
         if (isset($options['sort']) && ! is_array($options['sort']) && ! is_object($options['sort'])) {
@@ -205,7 +231,7 @@ class MapReduce implements Executable
         }
 
         if (isset($options['writeConcern']) && ! $options['writeConcern'] instanceof WriteConcern) {
-            throw InvalidArgumentException::invalidType('"writeConcern" option', $options['writeConcern'], 'MongoDB\Driver\WriteConcern');
+            throw InvalidArgumentException::invalidType('"writeConcern" option', $options['writeConcern'], WriteConcern::class);
         }
 
         if (isset($options['readConcern']) && $options['readConcern']->isDefault()) {
@@ -236,26 +262,46 @@ class MapReduce implements Executable
      */
     public function execute(Server $server)
     {
-        if (isset($this->options['collation']) && ! \MongoDB\server_supports_feature($server, self::$wireVersionForCollation)) {
+        if (isset($this->options['collation']) && ! server_supports_feature($server, self::$wireVersionForCollation)) {
             throw UnsupportedException::collationNotSupported();
         }
 
-        if (isset($this->options['readConcern']) && ! \MongoDB\server_supports_feature($server, self::$wireVersionForReadConcern)) {
+        if (isset($this->options['readConcern']) && ! server_supports_feature($server, self::$wireVersionForReadConcern)) {
             throw UnsupportedException::readConcernNotSupported();
         }
 
-        if (isset($this->options['writeConcern']) && ! \MongoDB\server_supports_feature($server, self::$wireVersionForWriteConcern)) {
+        if (isset($this->options['writeConcern']) && ! server_supports_feature($server, self::$wireVersionForWriteConcern)) {
             throw UnsupportedException::writeConcernNotSupported();
         }
 
-        $hasOutputCollection = ! \MongoDB\is_mapreduce_output_inline($this->out);
+        $inTransaction = isset($this->options['session']) && $this->options['session']->isInTransaction();
+        if ($inTransaction) {
+            if (isset($this->options['readConcern'])) {
+                throw UnsupportedException::readConcernNotSupportedInTransaction();
+            }
+            if (isset($this->options['writeConcern'])) {
+                throw UnsupportedException::writeConcernNotSupportedInTransaction();
+            }
+        }
+
+        $hasOutputCollection = ! is_mapreduce_output_inline($this->out);
 
         $command = $this->createCommand($server);
         $options = $this->createOptions($hasOutputCollection);
 
+        /* If the mapReduce operation results in a write, use
+         * executeReadWriteCommand to ensure we're handling the writeConcern
+         * option.
+         * In other cases, we use executeCommand as this will prevent the
+         * mapReduce operation from being retried when retryReads is enabled.
+         * See https://github.com/mongodb/specifications/blob/master/source/retryable-reads/retryable-reads.rst#unsupported-read-operations. */
         $cursor = $hasOutputCollection
             ? $server->executeReadWriteCommand($this->databaseName, $command, $options)
-            : $server->executeReadCommand($this->databaseName, $command, $options);
+            : $server->executeCommand($this->databaseName, $command, $options);
+
+        if (isset($this->options['typeMap']) && ! $hasOutputCollection) {
+            $cursor->setTypeMap(create_field_path_type_map($this->options['typeMap'], 'results.$'));
+        }
 
         $result = current($cursor->toArray());
 
@@ -291,7 +337,9 @@ class MapReduce implements Executable
             }
         }
 
-        if (isset($this->options['bypassDocumentValidation']) && \MongoDB\server_supports_feature($server, self::$wireVersionForDocumentLevelValidation)) {
+        if (! empty($this->options['bypassDocumentValidation']) &&
+            server_supports_feature($server, self::$wireVersionForDocumentLevelValidation)
+        ) {
             $cmd['bypassDocumentValidation'] = $this->options['bypassDocumentValidation'];
         }
 
@@ -312,11 +360,7 @@ class MapReduce implements Executable
         if (isset($result->results) && is_array($result->results)) {
             $results = $result->results;
 
-            return function() use ($results) {
-                if (isset($this->options['typeMap'])) {
-                    return new TypeMapArrayIterator($results, $this->options['typeMap']);
-                }
-
+            return function () use ($results) {
                 return new ArrayIterator($results);
             };
         }
@@ -328,7 +372,7 @@ class MapReduce implements Executable
                 ? new Find($this->databaseName, $result->result, [], $options)
                 : new Find($result->result->db, $result->result->collection, [], $options);
 
-            return function() use ($find, $server) {
+            return function () use ($find, $server) {
                 return $find->execute($server);
             };
         }
@@ -352,7 +396,7 @@ class MapReduce implements Executable
             $options['readConcern'] = $this->options['readConcern'];
         }
 
-        if ( ! $hasOutputCollection && isset($this->options['readPreference'])) {
+        if (! $hasOutputCollection && isset($this->options['readPreference'])) {
             $options['readPreference'] = $this->options['readPreference'];
         }
 
diff --git a/cache/stores/mongodb/MongoDB/Operation/ModifyCollection.php b/cache/stores/mongodb/MongoDB/Operation/ModifyCollection.php
index 5b84f8aaec8..0dc01115427 100644
--- a/cache/stores/mongodb/MongoDB/Operation/ModifyCollection.php
+++ b/cache/stores/mongodb/MongoDB/Operation/ModifyCollection.php
@@ -18,11 +18,15 @@
 namespace MongoDB\Operation;
 
 use MongoDB\Driver\Command;
+use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
 use MongoDB\Driver\Server;
 use MongoDB\Driver\Session;
 use MongoDB\Driver\WriteConcern;
-use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
 use MongoDB\Exception\InvalidArgumentException;
+use MongoDB\Exception\UnsupportedException;
+use function current;
+use function is_array;
+use function MongoDB\server_supports_feature;
 
 /**
  * Operation for the collMod command.
@@ -33,9 +37,16 @@ use MongoDB\Exception\InvalidArgumentException;
  */
 class ModifyCollection implements Executable
 {
+    /** @var string */
     private $databaseName;
+
+    /** @var string */
     private $collectionName;
+
+    /** @var array */
     private $collectionOptions;
+
+    /** @var array */
     private $options;
 
     /**
@@ -55,10 +66,10 @@ class ModifyCollection implements Executable
      *    This is not supported for server versions < 3.2 and will result in an
      *    exception at execution time if used.
      *
-     * @param string       $databaseName      Database name
-     * @param string       $collectionName    Collection or view to modify
-     * @param string       $collectionOptions Collection or view options to assign
-     * @param array        $options           Command options
+     * @param string $databaseName      Database name
+     * @param string $collectionName    Collection or view to modify
+     * @param array  $collectionOptions Collection or view options to assign
+     * @param array  $options           Command options
      * @throws InvalidArgumentException for parameter/option parsing errors
      */
     public function __construct($databaseName, $collectionName, array $collectionOptions, array $options = [])
@@ -68,7 +79,7 @@ class ModifyCollection implements Executable
         }
 
         if (isset($options['session']) && ! $options['session'] instanceof Session) {
-            throw InvalidArgumentException::invalidType('"session" option', $options['session'], 'MongoDB\Driver\Session');
+            throw InvalidArgumentException::invalidType('"session" option', $options['session'], Session::class);
         }
 
         if (isset($options['typeMap']) && ! is_array($options['typeMap'])) {
@@ -76,7 +87,7 @@ class ModifyCollection implements Executable
         }
 
         if (isset($options['writeConcern']) && ! $options['writeConcern'] instanceof WriteConcern) {
-            throw InvalidArgumentException::invalidType('"writeConcern" option', $options['writeConcern'], 'MongoDB\Driver\WriteConcern');
+            throw InvalidArgumentException::invalidType('"writeConcern" option', $options['writeConcern'], WriteConcern::class);
         }
 
         if (isset($options['writeConcern']) && $options['writeConcern']->isDefault()) {
@@ -99,7 +110,7 @@ class ModifyCollection implements Executable
      */
     public function execute(Server $server)
     {
-        if (isset($this->options['writeConcern']) && ! \MongoDB\server_supports_feature($server, self::$wireVersionForWriteConcern)) {
+        if (isset($this->options['writeConcern']) && ! server_supports_feature($server, self::$wireVersionForWriteConcern)) {
             throw UnsupportedException::writeConcernNotSupported();
         }
 
diff --git a/cache/stores/mongodb/MongoDB/Operation/ReplaceOne.php b/cache/stores/mongodb/MongoDB/Operation/ReplaceOne.php
index 86a196cc4cc..cbbda7ff289 100644
--- a/cache/stores/mongodb/MongoDB/Operation/ReplaceOne.php
+++ b/cache/stores/mongodb/MongoDB/Operation/ReplaceOne.php
@@ -17,11 +17,15 @@
 
 namespace MongoDB\Operation;
 
-use MongoDB\UpdateResult;
-use MongoDB\Driver\Server;
 use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
+use MongoDB\Driver\Server;
 use MongoDB\Exception\InvalidArgumentException;
 use MongoDB\Exception\UnsupportedException;
+use MongoDB\UpdateResult;
+use function is_array;
+use function is_object;
+use function MongoDB\is_first_key_operator;
+use function MongoDB\is_pipeline;
 
 /**
  * Operation for replacing a single document with the update command.
@@ -32,6 +36,7 @@ use MongoDB\Exception\UnsupportedException;
  */
 class ReplaceOne implements Executable
 {
+    /** @var Update */
     private $update;
 
     /**
@@ -68,14 +73,18 @@ class ReplaceOne implements Executable
      */
     public function __construct($databaseName, $collectionName, $filter, $replacement, array $options = [])
     {
-        if ( ! is_array($replacement) && ! is_object($replacement)) {
+        if (! is_array($replacement) && ! is_object($replacement)) {
             throw InvalidArgumentException::invalidType('$replacement', $replacement, 'array or object');
         }
 
-        if (\MongoDB\is_first_key_operator($replacement)) {
+        if (is_first_key_operator($replacement)) {
             throw new InvalidArgumentException('First key in $replacement argument is an update operator');
         }
 
+        if (is_pipeline($replacement)) {
+            throw new InvalidArgumentException('$replacement argument is a pipeline');
+        }
+
         $this->update = new Update(
             $databaseName,
             $collectionName,
diff --git a/cache/stores/mongodb/MongoDB/Operation/Update.php b/cache/stores/mongodb/MongoDB/Operation/Update.php
index 96adfa75889..e4ee30dbc0b 100644
--- a/cache/stores/mongodb/MongoDB/Operation/Update.php
+++ b/cache/stores/mongodb/MongoDB/Operation/Update.php
@@ -17,14 +17,20 @@
 
 namespace MongoDB\Operation;
 
-use MongoDB\UpdateResult;
 use MongoDB\Driver\BulkWrite as Bulk;
+use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
 use MongoDB\Driver\Server;
 use MongoDB\Driver\Session;
 use MongoDB\Driver\WriteConcern;
-use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
 use MongoDB\Exception\InvalidArgumentException;
 use MongoDB\Exception\UnsupportedException;
+use MongoDB\UpdateResult;
+use function is_array;
+use function is_bool;
+use function is_object;
+use function MongoDB\is_first_key_operator;
+use function MongoDB\is_pipeline;
+use function MongoDB\server_supports_feature;
 
 /**
  * Operation for the update command.
@@ -37,14 +43,28 @@ use MongoDB\Exception\UnsupportedException;
  */
 class Update implements Executable, Explainable
 {
+    /** @var integer */
     private static $wireVersionForArrayFilters = 6;
+
+    /** @var integer */
     private static $wireVersionForCollation = 5;
+
+    /** @var integer */
     private static $wireVersionForDocumentLevelValidation = 4;
 
+    /** @var string */
     private $databaseName;
+
+    /** @var string */
     private $collectionName;
+
+    /** @var array|object */
     private $filter;
+
+    /** @var array|object */
     private $update;
+
+    /** @var array */
     private $options;
 
     /**
@@ -92,11 +112,11 @@ class Update implements Executable, Explainable
      */
     public function __construct($databaseName, $collectionName, $filter, $update, array $options = [])
     {
-        if ( ! is_array($filter) && ! is_object($filter)) {
+        if (! is_array($filter) && ! is_object($filter)) {
             throw InvalidArgumentException::invalidType('$filter', $filter, 'array or object');
         }
 
-        if ( ! is_array($update) && ! is_object($update)) {
+        if (! is_array($update) && ! is_object($update)) {
             throw InvalidArgumentException::invalidType('$update', $filter, 'array or object');
         }
 
@@ -117,24 +137,24 @@ class Update implements Executable, Explainable
             throw InvalidArgumentException::invalidType('"collation" option', $options['collation'], 'array or object');
         }
 
-        if ( ! is_bool($options['multi'])) {
+        if (! is_bool($options['multi'])) {
             throw InvalidArgumentException::invalidType('"multi" option', $options['multi'], 'boolean');
         }
 
-        if ($options['multi'] && ! \MongoDB\is_first_key_operator($update)) {
+        if ($options['multi'] && ! is_first_key_operator($update) && ! is_pipeline($update)) {
             throw new InvalidArgumentException('"multi" option cannot be true if $update is a replacement document');
         }
 
         if (isset($options['session']) && ! $options['session'] instanceof Session) {
-            throw InvalidArgumentException::invalidType('"session" option', $options['session'], 'MongoDB\Driver\Session');
+            throw InvalidArgumentException::invalidType('"session" option', $options['session'], Session::class);
         }
 
-        if ( ! is_bool($options['upsert'])) {
+        if (! is_bool($options['upsert'])) {
             throw InvalidArgumentException::invalidType('"upsert" option', $options['upsert'], 'boolean');
         }
 
         if (isset($options['writeConcern']) && ! $options['writeConcern'] instanceof WriteConcern) {
-            throw InvalidArgumentException::invalidType('"writeConcern" option', $options['writeConcern'], 'MongoDB\Driver\WriteConcern');
+            throw InvalidArgumentException::invalidType('"writeConcern" option', $options['writeConcern'], WriteConcern::class);
         }
 
         if (isset($options['writeConcern']) && $options['writeConcern']->isDefault()) {
@@ -159,17 +179,24 @@ class Update implements Executable, Explainable
      */
     public function execute(Server $server)
     {
-        if (isset($this->options['arrayFilters']) && ! \MongoDB\server_supports_feature($server, self::$wireVersionForArrayFilters)) {
+        if (isset($this->options['arrayFilters']) && ! server_supports_feature($server, self::$wireVersionForArrayFilters)) {
             throw UnsupportedException::arrayFiltersNotSupported();
         }
 
-        if (isset($this->options['collation']) && ! \MongoDB\server_supports_feature($server, self::$wireVersionForCollation)) {
+        if (isset($this->options['collation']) && ! server_supports_feature($server, self::$wireVersionForCollation)) {
             throw UnsupportedException::collationNotSupported();
         }
 
+        $inTransaction = isset($this->options['session']) && $this->options['session']->isInTransaction();
+        if ($inTransaction && isset($this->options['writeConcern'])) {
+            throw UnsupportedException::writeConcernNotSupportedInTransaction();
+        }
+
         $bulkOptions = [];
 
-        if (isset($this->options['bypassDocumentValidation']) && \MongoDB\server_supports_feature($server, self::$wireVersionForDocumentLevelValidation)) {
+        if (! empty($this->options['bypassDocumentValidation']) &&
+            server_supports_feature($server, self::$wireVersionForDocumentLevelValidation)
+        ) {
             $bulkOptions['bypassDocumentValidation'] = $this->options['bypassDocumentValidation'];
         }
 
@@ -189,7 +216,9 @@ class Update implements Executable, Explainable
             $cmd['writeConcern'] = $this->options['writeConcern'];
         }
 
-        if (isset($this->options['bypassDocumentValidation']) && \MongoDB\server_supports_feature($server, self::$wireVersionForDocumentLevelValidation)) {
+        if (! empty($this->options['bypassDocumentValidation']) &&
+            server_supports_feature($server, self::$wireVersionForDocumentLevelValidation)
+        ) {
             $cmd['bypassDocumentValidation'] = $this->options['bypassDocumentValidation'];
         }
 
diff --git a/cache/stores/mongodb/MongoDB/Operation/UpdateMany.php b/cache/stores/mongodb/MongoDB/Operation/UpdateMany.php
index 1abd4012422..9138fe6811d 100644
--- a/cache/stores/mongodb/MongoDB/Operation/UpdateMany.php
+++ b/cache/stores/mongodb/MongoDB/Operation/UpdateMany.php
@@ -17,11 +17,15 @@
 
 namespace MongoDB\Operation;
 
-use MongoDB\UpdateResult;
-use MongoDB\Driver\Server;
 use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
+use MongoDB\Driver\Server;
 use MongoDB\Exception\InvalidArgumentException;
 use MongoDB\Exception\UnsupportedException;
+use MongoDB\UpdateResult;
+use function is_array;
+use function is_object;
+use function MongoDB\is_first_key_operator;
+use function MongoDB\is_pipeline;
 
 /**
  * Operation for updating multiple documents with the update command.
@@ -32,6 +36,7 @@ use MongoDB\Exception\UnsupportedException;
  */
 class UpdateMany implements Executable, Explainable
 {
+    /** @var Update */
     private $update;
 
     /**
@@ -74,12 +79,12 @@ class UpdateMany implements Executable, Explainable
      */
     public function __construct($databaseName, $collectionName, $filter, $update, array $options = [])
     {
-        if ( ! is_array($update) && ! is_object($update)) {
+        if (! is_array($update) && ! is_object($update)) {
             throw InvalidArgumentException::invalidType('$update', $update, 'array or object');
         }
 
-        if ( ! \MongoDB\is_first_key_operator($update)) {
-            throw new InvalidArgumentException('First key in $update argument is not an update operator');
+        if (! is_first_key_operator($update) && ! is_pipeline($update)) {
+            throw new InvalidArgumentException('Expected an update document with operator as first key or a pipeline');
         }
 
         $this->update = new Update(
diff --git a/cache/stores/mongodb/MongoDB/Operation/UpdateOne.php b/cache/stores/mongodb/MongoDB/Operation/UpdateOne.php
index 9ea8867f133..0c8d73a69c9 100644
--- a/cache/stores/mongodb/MongoDB/Operation/UpdateOne.php
+++ b/cache/stores/mongodb/MongoDB/Operation/UpdateOne.php
@@ -17,11 +17,15 @@
 
 namespace MongoDB\Operation;
 
-use MongoDB\UpdateResult;
-use MongoDB\Driver\Server;
 use MongoDB\Driver\Exception\RuntimeException as DriverRuntimeException;
+use MongoDB\Driver\Server;
 use MongoDB\Exception\InvalidArgumentException;
 use MongoDB\Exception\UnsupportedException;
+use MongoDB\UpdateResult;
+use function is_array;
+use function is_object;
+use function MongoDB\is_first_key_operator;
+use function MongoDB\is_pipeline;
 
 /**
  * Operation for updating a single document with the update command.
@@ -32,6 +36,7 @@ use MongoDB\Exception\UnsupportedException;
  */
 class UpdateOne implements Executable, Explainable
 {
+    /** @var Update */
     private $update;
 
     /**
@@ -74,12 +79,12 @@ class UpdateOne implements Executable, Explainable
      */
     public function __construct($databaseName, $collectionName, $filter, $update, array $options = [])
     {
-        if ( ! is_array($update) && ! is_object($update)) {
+        if (! is_array($update) && ! is_object($update)) {
             throw InvalidArgumentException::invalidType('$update', $update, 'array or object');
         }
 
-        if ( ! \MongoDB\is_first_key_operator($update)) {
-            throw new InvalidArgumentException('First key in $update argument is not an update operator');
+        if (! is_first_key_operator($update) && ! is_pipeline($update)) {
+            throw new InvalidArgumentException('Expected an update document with operator as first key or a pipeline');
         }
 
         $this->update = new Update(
diff --git a/cache/stores/mongodb/MongoDB/Operation/Watch.php b/cache/stores/mongodb/MongoDB/Operation/Watch.php
index a109bd93d26..ef301603b20 100644
--- a/cache/stores/mongodb/MongoDB/Operation/Watch.php
+++ b/cache/stores/mongodb/MongoDB/Operation/Watch.php
@@ -17,23 +17,31 @@
 
 namespace MongoDB\Operation;
 
-use MongoDB\ChangeStream;
 use MongoDB\BSON\TimestampInterface;
-use MongoDB\Driver\Command;
+use MongoDB\ChangeStream;
 use MongoDB\Driver\Cursor;
+use MongoDB\Driver\Exception\RuntimeException;
 use MongoDB\Driver\Manager;
-use MongoDB\Driver\ReadConcern;
+use MongoDB\Driver\Monitoring\CommandFailedEvent;
+use MongoDB\Driver\Monitoring\CommandStartedEvent;
+use MongoDB\Driver\Monitoring\CommandSubscriber;
+use MongoDB\Driver\Monitoring\CommandSucceededEvent;
 use MongoDB\Driver\ReadPreference;
 use MongoDB\Driver\Server;
-use MongoDB\Driver\Session;
-use MongoDB\Driver\Exception\RuntimeException;
-use MongoDB\Driver\Monitoring\CommandFailedEvent;
-use MongoDB\Driver\Monitoring\CommandSubscriber;
-use MongoDB\Driver\Monitoring\CommandStartedEvent;
-use MongoDB\Driver\Monitoring\CommandSucceededEvent;
 use MongoDB\Exception\InvalidArgumentException;
 use MongoDB\Exception\UnexpectedValueException;
 use MongoDB\Exception\UnsupportedException;
+use MongoDB\Model\ChangeStreamIterator;
+use function array_intersect_key;
+use function array_unshift;
+use function count;
+use function is_array;
+use function is_object;
+use function is_string;
+use function MongoDB\Driver\Monitoring\addSubscriber;
+use function MongoDB\Driver\Monitoring\removeSubscriber;
+use function MongoDB\select_server;
+use function MongoDB\server_supports_feature;
 
 /**
  * Operation for creating a change stream with the aggregate command.
@@ -47,19 +55,44 @@ use MongoDB\Exception\UnsupportedException;
  */
 class Watch implements Executable, /* @internal */ CommandSubscriber
 {
-    private static $wireVersionForOperationTime = 7;
-
     const FULL_DOCUMENT_DEFAULT = 'default';
     const FULL_DOCUMENT_UPDATE_LOOKUP = 'updateLookup';
 
+    /** @var integer */
+    private static $wireVersionForStartAtOperationTime = 7;
+
+    /** @var Aggregate */
     private $aggregate;
+
+    /** @var array */
     private $aggregateOptions;
+
+    /** @var array */
     private $changeStreamOptions;
+
+    /** @var string|null */
     private $collectionName;
+
+    /** @var string */
     private $databaseName;
+
+    /** @var integer|null */
+    private $firstBatchSize;
+
+    /** @var boolean */
+    private $hasResumed = false;
+
+    /** @var Manager */
+    private $manager;
+
+    /** @var TimestampInterface */
     private $operationTime;
+
+    /** @var array */
     private $pipeline;
-    private $resumeCallable;
+
+    /** @var object|null */
+    private $postBatchResumeToken;
 
     /**
      * Constructs an aggregate command for creating a change stream.
@@ -92,21 +125,31 @@ class Watch implements Executable, /* @internal */ CommandSubscriber
      *  * resumeAfter (document): Specifies the logical starting point for the
      *    new change stream.
      *
-     *    Using this option in conjunction with "startAtOperationTime" will
-     *    result in a server error. The options are mutually exclusive.
+     *    Using this option in conjunction with "startAfter" and/or
+     *    "startAtOperationTime" will result in a server error. The options are
+     *    mutually exclusive.
      *
      *  * session (MongoDB\Driver\Session): Client session.
      *
      *    Sessions are not supported for server versions < 3.6.
      *
+     *  * startAfter (document): Specifies the logical starting point for the
+     *    new change stream. Unlike "resumeAfter", this option can be used with
+     *    a resume token from an "invalidate" event.
+     *
+     *    Using this option in conjunction with "resumeAfter" and/or
+     *    "startAtOperationTime" will result in a server error. The options are
+     *    mutually exclusive.
+     *
      *  * startAtOperationTime (MongoDB\BSON\TimestampInterface): If specified,
      *    the change stream will only provide changes that occurred at or after
      *    the specified timestamp. Any command run against the server will
      *    return an operation time that can be used here. Alternatively, an
      *    operation time may be obtained from MongoDB\Driver\Server::getInfo().
      *
-     *    Using this option in conjunction with "resumeAfter" will result in a
-     *    server error. The options are mutually exclusive.
+     *    Using this option in conjunction with "resumeAfter" and/or
+     *    "startAfter" will result in a server error. The options are mutually
+     *    exclusive.
      *
      *    This option is not supported for server versions < 4.0.
      *
@@ -117,11 +160,11 @@ class Watch implements Executable, /* @internal */ CommandSubscriber
      * for the collection name. A cluster-level change stream may be created by
      * specifying null for both the database and collection name.
      *
-     * @param Manager        $manager        Manager instance from the driver
-     * @param string|null    $databaseName   Database name
-     * @param string|null    $collectionName Collection name
-     * @param array          $pipeline       List of pipeline operations
-     * @param array          $options        Command options
+     * @param Manager     $manager        Manager instance from the driver
+     * @param string|null $databaseName   Database name
+     * @param string|null $collectionName Collection name
+     * @param array       $pipeline       List of pipeline operations
+     * @param array       $options        Command options
      * @throws InvalidArgumentException for parameter/option parsing errors
      */
     public function __construct(Manager $manager, $databaseName, $collectionName, array $pipeline, array $options = [])
@@ -143,6 +186,10 @@ class Watch implements Executable, /* @internal */ CommandSubscriber
             throw InvalidArgumentException::invalidType('"resumeAfter" option', $options['resumeAfter'], 'array or object');
         }
 
+        if (isset($options['startAfter']) && ! is_array($options['startAfter']) && ! is_object($options['startAfter'])) {
+            throw InvalidArgumentException::invalidType('"startAfter" option', $options['startAfter'], 'array or object');
+        }
+
         if (isset($options['startAtOperationTime']) && ! $options['startAtOperationTime'] instanceof TimestampInterface) {
             throw InvalidArgumentException::invalidType('"startAtOperationTime" option', $options['startAtOperationTime'], TimestampInterface::class);
         }
@@ -152,7 +199,7 @@ class Watch implements Executable, /* @internal */ CommandSubscriber
          * ("implicit from the user's perspective" per PHPLIB-342). Since this
          * is filling in for an implicit session, we default "causalConsistency"
          * to false. */
-        if ( ! isset($options['session'])) {
+        if (! isset($options['session'])) {
             try {
                 $options['session'] = $manager->startSession(['causalConsistency' => false]);
             } catch (RuntimeException $e) {
@@ -162,7 +209,7 @@ class Watch implements Executable, /* @internal */ CommandSubscriber
         }
 
         $this->aggregateOptions = array_intersect_key($options, ['batchSize' => 1, 'collation' => 1, 'maxAwaitTimeMS' => 1, 'readConcern' => 1, 'readPreference' => 1, 'session' => 1, 'typeMap' => 1]);
-        $this->changeStreamOptions = array_intersect_key($options, ['fullDocument' => 1, 'resumeAfter' => 1, 'startAtOperationTime' => 1]);
+        $this->changeStreamOptions = array_intersect_key($options, ['fullDocument' => 1, 'resumeAfter' => 1, 'startAfter' => 1, 'startAtOperationTime' => 1]);
 
         // Null database name implies a cluster-wide change stream
         if ($databaseName === null) {
@@ -170,12 +217,12 @@ class Watch implements Executable, /* @internal */ CommandSubscriber
             $this->changeStreamOptions['allChangesForCluster'] = true;
         }
 
+        $this->manager = $manager;
         $this->databaseName = (string) $databaseName;
         $this->collectionName = isset($collectionName) ? (string) $collectionName : null;
         $this->pipeline = $pipeline;
 
         $this->aggregate = $this->createAggregate();
-        $this->resumeCallable = $this->createResumeCallable($manager);
     }
 
     /** @internal */
@@ -186,6 +233,12 @@ class Watch implements Executable, /* @internal */ CommandSubscriber
     /** @internal */
     final public function commandStarted(CommandStartedEvent $event)
     {
+        if ($event->getCommandName() !== 'aggregate') {
+            return;
+        }
+
+        $this->firstBatchSize = null;
+        $this->postBatchResumeToken = null;
     }
 
     /** @internal */
@@ -197,7 +250,18 @@ class Watch implements Executable, /* @internal */ CommandSubscriber
 
         $reply = $event->getReply();
 
-        if (isset($reply->operationTime) && $reply->operationTime instanceof TimestampInterface) {
+        if (! isset($reply->cursor->firstBatch) || ! is_array($reply->cursor->firstBatch)) {
+            throw new UnexpectedValueException('aggregate command did not return a "cursor.firstBatch" array');
+        }
+
+        $this->firstBatchSize = count($reply->cursor->firstBatch);
+
+        if (isset($reply->cursor->postBatchResumeToken) && is_object($reply->cursor->postBatchResumeToken)) {
+            $this->postBatchResumeToken = $reply->cursor->postBatchResumeToken;
+        }
+
+        if ($this->shouldCaptureOperationTime($event->getServer()) &&
+            isset($reply->operationTime) && $reply->operationTime instanceof TimestampInterface) {
             $this->operationTime = $reply->operationTime;
         }
     }
@@ -213,11 +277,16 @@ class Watch implements Executable, /* @internal */ CommandSubscriber
      */
     public function execute(Server $server)
     {
-        return new ChangeStream($this->executeAggregate($server), $this->resumeCallable);
+        return new ChangeStream(
+            $this->createChangeStreamIterator($server),
+            function ($resumeToken, $hasAdvanced) {
+                return $this->resume($resumeToken, $hasAdvanced);
+            }
+        );
     }
 
     /**
-     * Create the aggregate command for creating a change stream.
+     * Create the aggregate command for a change stream.
      *
      * This method is also used to recreate the aggregate command when resuming.
      *
@@ -231,56 +300,139 @@ class Watch implements Executable, /* @internal */ CommandSubscriber
         return new Aggregate($this->databaseName, $this->collectionName, $pipeline, $this->aggregateOptions);
     }
 
-    private function createResumeCallable(Manager $manager)
+    /**
+     * Create a ChangeStreamIterator by executing the aggregate command.
+     *
+     * @param Server $server
+     * @return ChangeStreamIterator
+     */
+    private function createChangeStreamIterator(Server $server)
     {
-        return function($resumeToken = null) use ($manager) {
-            /* If a resume token was provided, update the "resumeAfter" option
-             * and ensure that "startAtOperationTime" is no longer set. */
-            if ($resumeToken !== null) {
-                $this->changeStreamOptions['resumeAfter'] = $resumeToken;
-                unset($this->changeStreamOptions['startAtOperationTime']);
-            }
-
-            /* If we captured an operation time from the first aggregate command
-             * and there is no "resumeAfter" option, set "startAtOperationTime"
-             * so that we can resume from the original aggregate's time. */
-            if ($this->operationTime !== null && ! isset($this->changeStreamOptions['resumeAfter'])) {
-                $this->changeStreamOptions['startAtOperationTime'] = $this->operationTime;
-            }
-
-            $this->aggregate = $this->createAggregate();
-
-            /* Select a new server using the read preference, execute this
-             * operation on it, and return the new ChangeStream. */
-            $server = $manager->selectServer($this->aggregateOptions['readPreference']);
-
-            return $this->execute($server);
-        };
+        return new ChangeStreamIterator(
+            $this->executeAggregate($server),
+            $this->firstBatchSize,
+            $this->getInitialResumeToken(),
+            $this->postBatchResumeToken
+        );
     }
 
     /**
-     * Execute the aggregate command and optionally capture its operation time.
+     * Execute the aggregate command.
+     *
+     * The command will be executed using APM so that we can capture data from
+     * its response (e.g. firstBatch size, postBatchResumeToken).
      *
      * @param Server $server
      * @return Cursor
      */
     private function executeAggregate(Server $server)
     {
-        /* If we've already captured an operation time or the server does not
-         * support returning an operation time (e.g. MongoDB 3.6), execute the
-         * aggregation directly and return its cursor. */
-        if ($this->operationTime !== null || ! \MongoDB\server_supports_feature($server, self::$wireVersionForOperationTime)) {
-            return $this->aggregate->execute($server);
-        }
-
-        /* Otherwise, execute the aggregation using command monitoring so that
-         * we can capture its operation time with commandSucceeded(). */
-        \MongoDB\Driver\Monitoring\addSubscriber($this);
+        addSubscriber($this);
 
         try {
             return $this->aggregate->execute($server);
         } finally {
-            \MongoDB\Driver\Monitoring\removeSubscriber($this);
+            removeSubscriber($this);
         }
     }
+
+    /**
+     * Return the initial resume token for creating the ChangeStreamIterator.
+     *
+     * @see https://github.com/mongodb/specifications/blob/master/source/change-streams/change-streams.rst#updating-the-cached-resume-token
+     * @return array|object|null
+     */
+    private function getInitialResumeToken()
+    {
+        if ($this->firstBatchSize === 0 && isset($this->postBatchResumeToken)) {
+            return $this->postBatchResumeToken;
+        }
+
+        if (isset($this->changeStreamOptions['startAfter'])) {
+            return $this->changeStreamOptions['startAfter'];
+        }
+
+        if (isset($this->changeStreamOptions['resumeAfter'])) {
+            return $this->changeStreamOptions['resumeAfter'];
+        }
+
+        return null;
+    }
+
+    /**
+     * Resumes a change stream.
+     *
+     * @see https://github.com/mongodb/specifications/blob/master/source/change-streams/change-streams.rst#resume-process
+     * @param array|object|null $resumeToken
+     * @param bool              $hasAdvanced
+     * @return ChangeStreamIterator
+     * @throws InvalidArgumentException
+     */
+    private function resume($resumeToken = null, $hasAdvanced = false)
+    {
+        if (isset($resumeToken) && ! is_array($resumeToken) && ! is_object($resumeToken)) {
+            throw InvalidArgumentException::invalidType('$resumeToken', $resumeToken, 'array or object');
+        }
+
+        $this->hasResumed = true;
+
+        /* Select a new server using the original read preference. While watch
+         * is not usable within transactions, we still check if there is a
+         * pinned session. This is to avoid an ambiguous error message about
+         * running a command on the wrong server. */
+        $server = select_server($this->manager, $this->aggregateOptions);
+
+        $resumeOption = isset($this->changeStreamOptions['startAfter']) && ! $hasAdvanced ? 'startAfter' : 'resumeAfter';
+
+        unset($this->changeStreamOptions['resumeAfter']);
+        unset($this->changeStreamOptions['startAfter']);
+        unset($this->changeStreamOptions['startAtOperationTime']);
+
+        if ($resumeToken !== null) {
+            $this->changeStreamOptions[$resumeOption] = $resumeToken;
+        }
+
+        if ($resumeToken === null && $this->operationTime !== null) {
+            $this->changeStreamOptions['startAtOperationTime'] = $this->operationTime;
+        }
+
+        // Recreate the aggregate command and return a new ChangeStreamIterator
+        $this->aggregate = $this->createAggregate();
+
+        return $this->createChangeStreamIterator($server);
+    }
+
+    /**
+     * Determine whether to capture operation time from an aggregate response.
+     *
+     * @see https://github.com/mongodb/specifications/blob/master/source/change-streams/change-streams.rst#startatoperationtime
+     * @param Server $server
+     * @return boolean
+     */
+    private function shouldCaptureOperationTime(Server $server)
+    {
+        if ($this->hasResumed) {
+            return false;
+        }
+
+        if (isset($this->changeStreamOptions['resumeAfter']) ||
+            isset($this->changeStreamOptions['startAfter']) ||
+            isset($this->changeStreamOptions['startAtOperationTime'])) {
+            return false;
+        }
+
+        if ($this->firstBatchSize > 0) {
+            return false;
+        }
+
+        if ($this->postBatchResumeToken !== null) {
+            return false;
+        }
+
+        if (! server_supports_feature($server, self::$wireVersionForStartAtOperationTime)) {
+            return false;
+        }
+
+        return true;
+    }
 }
diff --git a/cache/stores/mongodb/MongoDB/Operation/WithTransaction.php b/cache/stores/mongodb/MongoDB/Operation/WithTransaction.php
new file mode 100644
index 00000000000..249616e6c83
--- /dev/null
+++ b/cache/stores/mongodb/MongoDB/Operation/WithTransaction.php
@@ -0,0 +1,127 @@
+<?php
+
+namespace MongoDB\Operation;
+
+use Exception;
+use MongoDB\Driver\Exception\RuntimeException;
+use MongoDB\Driver\Session;
+use function call_user_func;
+use function time;
+
+/**
+ * @internal
+ */
+class WithTransaction
+{
+    /** @var callable */
+    private $callback;
+
+    /** @var array */
+    private $transactionOptions;
+
+    /**
+     * @see Session::startTransaction for supported transaction options
+     *
+     * @param callable $callback           A callback that will be invoked within the transaction
+     * @param array    $transactionOptions Additional options that are passed to Session::startTransaction
+     */
+    public function __construct(callable $callback, array $transactionOptions = [])
+    {
+        $this->callback = $callback;
+        $this->transactionOptions = $transactionOptions;
+    }
+
+    /**
+     * Execute the operation in the given session
+     *
+     * This helper takes care of retrying the commit operation or the entire
+     * transaction if an error occurs.
+     *
+     * If the commit fails because of an UnknownTransactionCommitResult error, the
+     * commit is retried without re-invoking the callback.
+     * If the commit fails because of a TransientTransactionError, the entire
+     * transaction will be retried. In this case, the callback will be invoked
+     * again. It is important that the logic inside the callback is idempotent.
+     *
+     * In case of failures, the commit or transaction are retried until 120 seconds
+     * from the initial call have elapsed. After that, no retries will happen and
+     * the helper will throw the last exception received from the driver.
+     *
+     * @see Client::startSession
+     *
+     * @param Session $session A session object as retrieved by Client::startSession
+     * @return void
+     * @throws RuntimeException for driver errors while committing the transaction
+     * @throws Exception for any other errors, including those thrown in the callback
+     */
+    public function execute(Session $session)
+    {
+        $startTime = time();
+
+        while (true) {
+            $session->startTransaction($this->transactionOptions);
+
+            try {
+                call_user_func($this->callback, $session);
+            } catch (Exception $e) {
+                if ($session->isInTransaction()) {
+                    $session->abortTransaction();
+                }
+
+                if ($e instanceof RuntimeException &&
+                    $e->hasErrorLabel('TransientTransactionError') &&
+                    ! $this->isTransactionTimeLimitExceeded($startTime)
+                ) {
+                    continue;
+                }
+
+                throw $e;
+            }
+
+            if (! $session->isInTransaction()) {
+                // Assume callback intentionally ended the transaction
+                return;
+            }
+
+            while (true) {
+                try {
+                    $session->commitTransaction();
+                } catch (RuntimeException $e) {
+                    if ($e->getCode() !== 50 /* MaxTimeMSExpired */ &&
+                        $e->hasErrorLabel('UnknownTransactionCommitResult') &&
+                        ! $this->isTransactionTimeLimitExceeded($startTime)
+                    ) {
+                        // Retry committing the transaction
+                        continue;
+                    }
+
+                    if ($e->hasErrorLabel('TransientTransactionError') &&
+                        ! $this->isTransactionTimeLimitExceeded($startTime)
+                    ) {
+                        // Restart the transaction, invoking the callback again
+                        continue 2;
+                    }
+
+                    throw $e;
+                }
+
+                // Commit was successful
+                break;
+            }
+
+            // Transaction was successful
+            break;
+        }
+    }
+
+    /**
+     * Returns whether the time limit for retrying transactions in the convenient transaction API has passed
+     *
+     * @param int $startTime The time the transaction was started
+     * @return bool
+     */
+    private function isTransactionTimeLimitExceeded($startTime)
+    {
+        return time() - $startTime >= 120;
+    }
+}
diff --git a/cache/stores/mongodb/MongoDB/UpdateResult.php b/cache/stores/mongodb/MongoDB/UpdateResult.php
index a19173f94c5..62660d2cade 100644
--- a/cache/stores/mongodb/MongoDB/UpdateResult.php
+++ b/cache/stores/mongodb/MongoDB/UpdateResult.php
@@ -25,14 +25,12 @@ use MongoDB\Exception\BadMethodCallException;
  */
 class UpdateResult
 {
+    /** @var WriteResult */
     private $writeResult;
+
+    /** @var boolean */
     private $isAcknowledged;
 
-    /**
-     * Constructor.
-     *
-     * @param WriteResult $writeResult
-     */
     public function __construct(WriteResult $writeResult)
     {
         $this->writeResult = $writeResult;
diff --git a/cache/stores/mongodb/MongoDB/functions.php b/cache/stores/mongodb/MongoDB/functions.php
index f37226866d7..e828e669a4b 100644
--- a/cache/stores/mongodb/MongoDB/functions.php
+++ b/cache/stores/mongodb/MongoDB/functions.php
@@ -17,13 +17,28 @@
 
 namespace MongoDB;
 
+use Exception;
 use MongoDB\BSON\Serializable;
-use MongoDB\Driver\ReadConcern;
+use MongoDB\Driver\Manager;
+use MongoDB\Driver\ReadPreference;
 use MongoDB\Driver\Server;
-use MongoDB\Driver\WriteConcern;
+use MongoDB\Driver\Session;
 use MongoDB\Exception\InvalidArgumentException;
-use stdClass;
+use MongoDB\Exception\RuntimeException;
+use MongoDB\Operation\WithTransaction;
 use ReflectionClass;
+use ReflectionException;
+use function end;
+use function get_object_vars;
+use function in_array;
+use function is_array;
+use function is_object;
+use function is_string;
+use function key;
+use function MongoDB\BSON\fromPHP;
+use function MongoDB\BSON\toPHP;
+use function reset;
+use function substr;
 
 /**
  * Applies a type map to a document.
@@ -40,11 +55,11 @@ use ReflectionClass;
  */
 function apply_type_map_to_document($document, array $typeMap)
 {
-    if ( ! is_array($document) && ! is_object($document)) {
+    if (! is_array($document) && ! is_object($document)) {
         throw InvalidArgumentException::invalidType('$document', $document, 'array or object');
     }
 
-    return \MongoDB\BSON\toPHP(\MongoDB\BSON\fromPHP($document), $typeMap);
+    return toPHP(fromPHP($document), $typeMap);
 }
 
 /**
@@ -66,7 +81,7 @@ function generate_index_name($document)
         $document = get_object_vars($document);
     }
 
-    if ( ! is_array($document)) {
+    if (! is_array($document)) {
         throw InvalidArgumentException::invalidType('$document', $document, 'array or object');
     }
 
@@ -99,18 +114,75 @@ function is_first_key_operator($document)
         $document = get_object_vars($document);
     }
 
-    if ( ! is_array($document)) {
+    if (! is_array($document)) {
         throw InvalidArgumentException::invalidType('$document', $document, 'array or object');
     }
 
     reset($document);
     $firstKey = (string) key($document);
 
-    return (isset($firstKey[0]) && $firstKey[0] === '$');
+    return isset($firstKey[0]) && $firstKey[0] === '$';
 }
 
 /**
- * Return whether the aggregation pipeline ends with an $out operator.
+ * Returns whether an update specification is a valid aggregation pipeline.
+ *
+ * @internal
+ * @param mixed $pipeline
+ * @return boolean
+ */
+function is_pipeline($pipeline)
+{
+    if (! is_array($pipeline)) {
+        return false;
+    }
+
+    if ($pipeline === []) {
+        return false;
+    }
+
+    $expectedKey = 0;
+
+    foreach ($pipeline as $key => $stage) {
+        if (! is_array($stage) && ! is_object($stage)) {
+            return false;
+        }
+
+        if ($expectedKey !== $key) {
+            return false;
+        }
+
+        $expectedKey++;
+        $stage = (array) $stage;
+        reset($stage);
+        $key = key($stage);
+
+        if (! isset($key[0]) || $key[0] !== '$') {
+            return false;
+        }
+    }
+
+    return true;
+}
+
+/**
+ * Returns whether we are currently in a transaction.
+ *
+ * @internal
+ * @param array $options Command options
+ * @return boolean
+ */
+function is_in_transaction(array $options)
+{
+    if (isset($options['session']) && $options['session'] instanceof Session && $options['session']->isInTransaction()) {
+        return true;
+    }
+
+    return false;
+}
+
+/**
+ * Return whether the aggregation pipeline ends with an $out or $merge operator.
  *
  * This is used for determining whether the aggregation pipeline must be
  * executed against a primary server.
@@ -119,7 +191,7 @@ function is_first_key_operator($document)
  * @param array $pipeline List of pipeline operations
  * @return boolean
  */
-function is_last_pipeline_operator_out(array $pipeline)
+function is_last_pipeline_operator_write(array $pipeline)
 {
     $lastOp = end($pipeline);
 
@@ -129,7 +201,7 @@ function is_last_pipeline_operator_out(array $pipeline)
 
     $lastOp = (array) $lastOp;
 
-    return key($lastOp) === '$out';
+    return in_array(key($lastOp), ['$out', '$merge'], true);
 }
 
 /**
@@ -145,7 +217,7 @@ function is_last_pipeline_operator_out(array $pipeline)
  */
 function is_mapreduce_output_inline($out)
 {
-    if ( ! is_array($out) && ! is_object($out)) {
+    if (! is_array($out) && ! is_object($out)) {
         return false;
     }
 
@@ -157,7 +229,7 @@ function is_mapreduce_output_inline($out)
         $out = get_object_vars($out);
     }
 
-    if ( ! is_array($out)) {
+    if (! is_array($out)) {
         throw InvalidArgumentException::invalidType('$out', $out, 'array or object');
     }
 
@@ -180,18 +252,20 @@ function server_supports_feature(Server $server, $feature)
     $maxWireVersion = isset($info['maxWireVersion']) ? (integer) $info['maxWireVersion'] : 0;
     $minWireVersion = isset($info['minWireVersion']) ? (integer) $info['minWireVersion'] : 0;
 
-    return ($minWireVersion <= $feature && $maxWireVersion >= $feature);
+    return $minWireVersion <= $feature && $maxWireVersion >= $feature;
 }
 
-function is_string_array($input) {
-    if (!is_array($input)){
+function is_string_array($input)
+{
+    if (! is_array($input)) {
         return false;
     }
-    foreach($input as $item) {
-        if (!is_string($item)) {
+    foreach ($input as $item) {
+        if (! is_string($item)) {
             return false;
         }
     }
+
     return true;
 }
 
@@ -204,22 +278,155 @@ function is_string_array($input) {
  * @see https://bugs.php.net/bug.php?id=49664
  * @param mixed $element Value to be copied
  * @return mixed
+ * @throws ReflectionException
  */
-function recursive_copy($element) {
+function recursive_copy($element)
+{
     if (is_array($element)) {
         foreach ($element as $key => $value) {
             $element[$key] = recursive_copy($value);
         }
+
         return $element;
     }
 
-    if ( ! is_object($element)) {
+    if (! is_object($element)) {
         return $element;
     }
 
-    if ( ! (new ReflectionClass($element))->isCloneable()) {
+    if (! (new ReflectionClass($element))->isCloneable()) {
         return $element;
     }
 
     return clone $element;
 }
+
+/**
+ * Creates a type map to apply to a field type
+ *
+ * This is used in the Aggregate, Distinct, and FindAndModify operations to
+ * apply the root-level type map to the document that will be returned. It also
+ * replaces the root type with object for consistency within these operations
+ *
+ * An existing type map for the given field path will not be overwritten
+ *
+ * @internal
+ * @param array  $typeMap   The existing typeMap
+ * @param string $fieldPath The field path to apply the root type to
+ * @return array
+ */
+function create_field_path_type_map(array $typeMap, $fieldPath)
+{
+    // If some field paths already exist, we prefix them with the field path we are assuming as the new root
+    if (isset($typeMap['fieldPaths']) && is_array($typeMap['fieldPaths'])) {
+        $fieldPaths = $typeMap['fieldPaths'];
+
+        $typeMap['fieldPaths'] = [];
+        foreach ($fieldPaths as $existingFieldPath => $type) {
+            $typeMap['fieldPaths'][$fieldPath . '.' . $existingFieldPath] = $type;
+        }
+    }
+
+    // If a root typemap was set, apply this to the field object
+    if (isset($typeMap['root'])) {
+        $typeMap['fieldPaths'][$fieldPath] = $typeMap['root'];
+    }
+
+    /* Special case if we want to convert an array, in which case we need to
+     * ensure that the field containing the array is exposed as an array,
+     * instead of the type given in the type map's array key. */
+    if (substr($fieldPath, -2, 2) === '.$') {
+        $typeMap['fieldPaths'][substr($fieldPath, 0, -2)] = 'array';
+    }
+
+    $typeMap['root'] = 'object';
+
+    return $typeMap;
+}
+
+/**
+ * Execute a callback within a transaction in the given session
+ *
+ * This helper takes care of retrying the commit operation or the entire
+ * transaction if an error occurs.
+ *
+ * If the commit fails because of an UnknownTransactionCommitResult error, the
+ * commit is retried without re-invoking the callback.
+ * If the commit fails because of a TransientTransactionError, the entire
+ * transaction will be retried. In this case, the callback will be invoked
+ * again. It is important that the logic inside the callback is idempotent.
+ *
+ * In case of failures, the commit or transaction are retried until 120 seconds
+ * from the initial call have elapsed. After that, no retries will happen and
+ * the helper will throw the last exception received from the driver.
+ *
+ * @see Client::startSession
+ * @see Session::startTransaction for supported transaction options
+ *
+ * @param Session  $session            A session object as retrieved by Client::startSession
+ * @param callable $callback           A callback that will be invoked within the transaction
+ * @param array    $transactionOptions Additional options that are passed to Session::startTransaction
+ * @return void
+ * @throws RuntimeException for driver errors while committing the transaction
+ * @throws Exception for any other errors, including those thrown in the callback
+ */
+function with_transaction(Session $session, callable $callback, array $transactionOptions = [])
+{
+    $operation = new WithTransaction($callback, $transactionOptions);
+    $operation->execute($session);
+}
+
+/**
+ * Returns the session option if it is set and valid.
+ *
+ * @internal
+ * @param array $options
+ * @return Session|null
+ */
+function extract_session_from_options(array $options)
+{
+    if (! isset($options['session']) || ! $options['session'] instanceof Session) {
+        return null;
+    }
+
+    return $options['session'];
+}
+
+/**
+ * Returns the readPreference option if it is set and valid.
+ *
+ * @internal
+ * @param array $options
+ * @return ReadPreference|null
+ */
+function extract_read_preference_from_options(array $options)
+{
+    if (! isset($options['readPreference']) || ! $options['readPreference'] instanceof ReadPreference) {
+        return null;
+    }
+
+    return $options['readPreference'];
+}
+
+/**
+ * Performs server selection, respecting the readPreference and session options
+ * (if given)
+ *
+ * @internal
+ * @return Server
+ */
+function select_server(Manager $manager, array $options)
+{
+    $session = extract_session_from_options($options);
+    if ($session instanceof Session && $session->getServer() !== null) {
+        return $session->getServer();
+    }
+
+    $readPreference = extract_read_preference_from_options($options);
+    if (! $readPreference instanceof ReadPreference) {
+        // TODO: PHPLIB-476: Read transaction read preference once PHPC-1439 is implemented
+        $readPreference = new ReadPreference(ReadPreference::RP_PRIMARY);
+    }
+
+    return $manager->selectServer($readPreference);
+}
diff --git a/cache/stores/mongodb/readme_moodle.txt b/cache/stores/mongodb/readme_moodle.txt
index 16b905a3370..33283da33a2 100644
--- a/cache/stores/mongodb/readme_moodle.txt
+++ b/cache/stores/mongodb/readme_moodle.txt
@@ -1,6 +1,6 @@
 MongoDB PHP
 -----------
-Download from https://github.com/mongodb/mongo-php-library
+Download from https://github.com/mongodb/mongo-php-library/releases
 
 Import procedure:
 
@@ -8,8 +8,4 @@ Import procedure:
 - Copy the license file from the project root.
 - Update thirdpartylibs.xml with the latest version.
 
-2019/03/14
-----------
-Last commit on download: aac8e54009196f6544e50baf9b63dcf0eab3bbdf
-
-This version (1.4.2) requires PHP mongodb extension >= 1.5
+This version (1.5.1) requires PHP mongodb extension >= 1.6.0
diff --git a/cache/stores/mongodb/thirdpartylibs.xml b/cache/stores/mongodb/thirdpartylibs.xml
index afc8de0e7c4..f92af41ed07 100644
--- a/cache/stores/mongodb/thirdpartylibs.xml
+++ b/cache/stores/mongodb/thirdpartylibs.xml
@@ -4,7 +4,7 @@
     <location>MongoDB</location>
     <name>MongoDB PHP Library</name>
     <license>Apache</license>
-    <version>1.4.2</version>
+    <version>1.5.1</version>
     <licenseversion>2.0</licenseversion>
   </library>
 </libraries>
\ No newline at end of file