diff --git a/admin/cli/fix_deleted_users.php b/admin/cli/fix_deleted_users.php
index d2a895057a2..cc052b4e702 100644
--- a/admin/cli/fix_deleted_users.php
+++ b/admin/cli/fix_deleted_users.php
@@ -73,6 +73,7 @@ foreach ($rs as $user) {
     echo "Redeleting user $user->id: $user->username ($user->email)\n";
     delete_user($user);
 }
+$rs->close();
 
 cli_heading('Deleting all leftovers');
 
diff --git a/admin/tool/messageinbound/index.php b/admin/tool/messageinbound/index.php
index 8d04d450aed..90c2a128933 100644
--- a/admin/tool/messageinbound/index.php
+++ b/admin/tool/messageinbound/index.php
@@ -40,6 +40,7 @@ if (empty($classname)) {
     foreach ($records as $record) {
         $instances[] = \core\message\inbound\manager::get_handler($record->classname);
     }
+    $records->close();
 
     echo $OUTPUT->header();
     echo $renderer->messageinbound_handlers_table($instances);
diff --git a/admin/tool/spamcleaner/index.php b/admin/tool/spamcleaner/index.php
index 63d3485e5dd..2f98bf41006 100644
--- a/admin/tool/spamcleaner/index.php
+++ b/admin/tool/spamcleaner/index.php
@@ -234,15 +234,19 @@ function search_spammers($keywords) {
     $keywordlist = implode(', ', $keywords);
     echo $OUTPUT->box(get_string('spamresult', 'tool_spamcleaner').s($keywordlist)).' ...';
 
-    print_user_list(array($spamusers_desc,
-                          $spamusers_blog,
-                          $spamusers_blogsub,
-                          $spamusers_comment,
-                          $spamusers_message,
-                          $spamusers_forumpost,
-                          $spamusers_forumpostsub
-                         ),
-                         $keywords);
+    $recordsets = [
+        $spamusers_desc,
+        $spamusers_blog,
+        $spamusers_blogsub,
+        $spamusers_comment,
+        $spamusers_message,
+        $spamusers_forumpost,
+        $spamusers_forumpostsub
+    ];
+    print_user_list($recordsets, $keywords);
+    foreach ($recordsets as $rs) {
+        $rs->close();
+    }
 }
 
 
diff --git a/analytics/classes/manager.php b/analytics/classes/manager.php
index 4b0bcac480d..cdf787e2853 100644
--- a/analytics/classes/manager.php
+++ b/analytics/classes/manager.php
@@ -360,6 +360,7 @@ class manager {
             }
             $existingcalculations[$calculation->indicator][$calculation->sampleid] = $calculation->value;
         }
+        $calculations->close();
         return $existingcalculations;
     }
 
diff --git a/backup/moodle2/restore_stepslib.php b/backup/moodle2/restore_stepslib.php
index 9b87054f72e..529645f9bf8 100644
--- a/backup/moodle2/restore_stepslib.php
+++ b/backup/moodle2/restore_stepslib.php
@@ -981,8 +981,8 @@ class restore_process_course_modules_availability extends restore_execution_step
                 $DB->set_field('course_' . $table . 's', 'availability', $newvalue,
                         array('id' => $thingid));
             }
+            $rs->close();
         }
-        $rs->close();
     }
 }
 
diff --git a/cohort/lib.php b/cohort/lib.php
index c319946dc7a..f3c3a16a933 100644
--- a/cohort/lib.php
+++ b/cohort/lib.php
@@ -507,6 +507,7 @@ function cohort_get_invisible_contexts() {
             $excludedcontexts[] = $ctx->id;
         }
     }
+    $records->close();
     return $excludedcontexts;
 }
 
diff --git a/grade/grading/form/lib.php b/grade/grading/form/lib.php
index b79f5c77362..2f0666221df 100644
--- a/grade/grading/form/lib.php
+++ b/grade/grading/form/lib.php
@@ -428,6 +428,7 @@ abstract class gradingform_controller {
         foreach ($records as $record) {
             $rv[] = $this->get_instance($record);
         }
+        $records->close();
         return $rv;
     }
 
diff --git a/grade/report/singleview/classes/local/screen/screen.php b/grade/report/singleview/classes/local/screen/screen.php
index 56709dfcb6f..db3ecb601e3 100644
--- a/grade/report/singleview/classes/local/screen/screen.php
+++ b/grade/report/singleview/classes/local/screen/screen.php
@@ -419,6 +419,7 @@ abstract class screen {
         while ($user = $gui->next_user()) {
             $users[$user->user->id] = $user->user;
         }
+        $gui->close();
         return $users;
     }
 
diff --git a/group/lib.php b/group/lib.php
index 99a4c6ec309..57bd61610da 100644
--- a/group/lib.php
+++ b/group/lib.php
@@ -628,6 +628,7 @@ function groups_delete_groupings_groups($courseid, $showfeedback=false) {
     foreach ($results as $result) {
         groups_unassign_grouping($result->groupingid, $result->groupid, false);
     }
+    $results->close();
 
     // Invalidate the grouping cache for the course
     cache_helper::invalidate_by_definition('core', 'groupdata', array(), array($courseid));
@@ -658,6 +659,7 @@ function groups_delete_groups($courseid, $showfeedback=false) {
     foreach ($groups as $group) {
         groups_delete_group($group);
     }
+    $groups->close();
 
     // Invalidate the grouping cache for the course
     cache_helper::invalidate_by_definition('core', 'groupdata', array(), array($courseid));
@@ -690,6 +692,7 @@ function groups_delete_groupings($courseid, $showfeedback=false) {
     foreach ($groupings as $grouping) {
         groups_delete_grouping($grouping);
     }
+    $groupings->close();
 
     // Invalidate the grouping cache for the course.
     cache_helper::invalidate_by_definition('core', 'groupdata', array(), array($courseid));
diff --git a/lib/blocklib.php b/lib/blocklib.php
index 7e2d79b6707..c8fa2455a08 100644
--- a/lib/blocklib.php
+++ b/lib/blocklib.php
@@ -800,6 +800,7 @@ class block_manager {
                 $unknown[] = $bi;
             }
         }
+        $blockinstances->close();
 
         // Pages don't necessarily have a defaultregion. The  one time this can
         // happen is when there are no theme block regions, but the script itself
diff --git a/lib/classes/message/inbound/manager.php b/lib/classes/message/inbound/manager.php
index 8534df679e4..9bc16cddb38 100644
--- a/lib/classes/message/inbound/manager.php
+++ b/lib/classes/message/inbound/manager.php
@@ -74,6 +74,7 @@ class manager {
                 self::remove_messageinbound_handler($handler);
             }
         }
+        $existinghandlers->close();
 
         self::create_missing_messageinbound_handlers_for_component($componentname);
     }
diff --git a/lib/classes/plugininfo/portfolio.php b/lib/classes/plugininfo/portfolio.php
index 78e94f40a96..80f57d50c77 100644
--- a/lib/classes/plugininfo/portfolio.php
+++ b/lib/classes/plugininfo/portfolio.php
@@ -43,6 +43,7 @@ class portfolio extends base {
         foreach ($rs as $repository) {
             $enabled[$repository->plugin] = $repository->plugin;
         }
+        $rs->close();
 
         return $enabled;
     }
@@ -91,4 +92,4 @@ class portfolio extends base {
 
         parent::uninstall_cleanup();
     }
-}
\ No newline at end of file
+}
diff --git a/lib/db/upgrade.php b/lib/db/upgrade.php
index a731b661628..376a3010071 100644
--- a/lib/db/upgrade.php
+++ b/lib/db/upgrade.php
@@ -1183,6 +1183,7 @@ function xmldb_main_upgrade($oldversion) {
             $i++;
             $pbar->update($i, $total, "Updating duplicate question category stamp - $i/$total.");
         }
+        $rs->close();
         unset($usedstamps);
 
         // The uniqueness of each (contextid, stamp) pair is now guaranteed, so add the unique index to stop future duplicates.
diff --git a/lib/filestorage/file_storage.php b/lib/filestorage/file_storage.php
index e15d0715d17..2c1906db990 100644
--- a/lib/filestorage/file_storage.php
+++ b/lib/filestorage/file_storage.php
@@ -2001,6 +2001,7 @@ class file_storage {
         foreach ($rs as $filerecord) {
             $files[$filerecord->pathnamehash] = $this->get_file_instance($filerecord);
         }
+        $rs->close();
 
         return $files;
     }
diff --git a/lib/navigationlib.php b/lib/navigationlib.php
index 11ef46b7200..226d024c199 100644
--- a/lib/navigationlib.php
+++ b/lib/navigationlib.php
@@ -3258,6 +3258,7 @@ class global_navigation_for_ajax extends global_navigation {
                 foreach ($categories as $category){
                     $coursesubcategories = array_merge($coursesubcategories, explode('/', trim($category->path, "/")));
                 }
+                $categories->close();
                 $coursesubcategories = array_unique($coursesubcategories);
 
                 // Only add a subcategory if it is part of the path to user's course and
diff --git a/lib/tablelib.php b/lib/tablelib.php
index d1f1adc0b4e..835c751e522 100644
--- a/lib/tablelib.php
+++ b/lib/tablelib.php
@@ -1499,9 +1499,9 @@ class table_sql extends flexible_table {
      * method or if other_cols returns NULL then put the data straight into the
      * table.
      *
-     * @return void
+     * After calling this function, don't forget to call close_recordset.
      */
-    function build_table() {
+    public function build_table() {
 
         if ($this->rawdata instanceof \Traversable && !$this->rawdata->valid()) {
             return;
@@ -1515,10 +1515,16 @@ class table_sql extends flexible_table {
             $this->add_data_keyed($formattedrow,
                 $this->get_row_class($row));
         }
+    }
 
-        if ($this->rawdata instanceof \core\dml\recordset_walk ||
-                $this->rawdata instanceof moodle_recordset) {
+    /**
+     * Closes recordset (for use after building the table).
+     */
+    public function close_recordset() {
+        if ($this->rawdata && ($this->rawdata instanceof \core\dml\recordset_walk ||
+                $this->rawdata instanceof moodle_recordset)) {
             $this->rawdata->close();
+            $this->rawdata = null;
         }
     }
 
@@ -1629,6 +1635,7 @@ class table_sql extends flexible_table {
         $this->setup();
         $this->query_db($pagesize, $useinitialsbar);
         $this->build_table();
+        $this->close_recordset();
         $this->finish_output();
     }
 }
diff --git a/lib/testing/classes/util.php b/lib/testing/classes/util.php
index 4a8b682e133..533200850a6 100644
--- a/lib/testing/classes/util.php
+++ b/lib/testing/classes/util.php
@@ -676,6 +676,7 @@ abstract class testing_util {
                     $mysqlsequences[$table] = $info->auto_increment;
                 }
             }
+            $rs->close();
         }
 
         foreach ($data as $table => $records) {
diff --git a/message/tests/externallib_test.php b/message/tests/externallib_test.php
index 8f28c29dc93..b7392f18833 100644
--- a/message/tests/externallib_test.php
+++ b/message/tests/externallib_test.php
@@ -902,15 +902,15 @@ class core_message_externallib_testcase extends externallib_advanced_testcase {
         $this->send_message($sender3, $recipient, 'Notification', 1);
 
         core_message_external::mark_all_notifications_as_read($recipient->id, $sender1->id);
-        $readnotifications = $DB->get_recordset('message_read', ['useridto' => $recipient->id]);
-        $unreadnotifications = $DB->get_recordset('message', ['useridto' => $recipient->id]);
+        $readnotifications = $DB->get_records('message_read', ['useridto' => $recipient->id]);
+        $unreadnotifications = $DB->get_records('message', ['useridto' => $recipient->id]);
 
         $this->assertCount(2, $readnotifications);
         $this->assertCount(4, $unreadnotifications);
 
         core_message_external::mark_all_notifications_as_read($recipient->id, 0);
-        $readnotifications = $DB->get_recordset('message_read', ['useridto' => $recipient->id]);
-        $unreadnotifications = $DB->get_recordset('message', ['useridto' => $recipient->id]);
+        $readnotifications = $DB->get_records('message_read', ['useridto' => $recipient->id]);
+        $unreadnotifications = $DB->get_records('message', ['useridto' => $recipient->id]);
 
         $this->assertCount(6, $readnotifications);
         $this->assertCount(0, $unreadnotifications);
diff --git a/mod/feedback/classes/responses_table.php b/mod/feedback/classes/responses_table.php
index 9426775eba1..50b7d9efbff 100644
--- a/mod/feedback/classes/responses_table.php
+++ b/mod/feedback/classes/responses_table.php
@@ -504,8 +504,6 @@ class mod_feedback_responses_table extends table_sql {
             }
         }
         $this->build_table_chunk($chunk, $columnsgroups);
-
-        $this->rawdata->close();
     }
 
     /**
@@ -631,6 +629,7 @@ class mod_feedback_responses_table extends table_sql {
         }
         $this->query_db($this->pagesize, false);
         $this->build_table();
+        $this->close_recordset();
         return $this->dataforexternal;
     }
 }
diff --git a/mod/forum/tests/subscriptions_test.php b/mod/forum/tests/subscriptions_test.php
index f435f00b982..276ccf7d081 100644
--- a/mod/forum/tests/subscriptions_test.php
+++ b/mod/forum/tests/subscriptions_test.php
@@ -28,11 +28,12 @@ global $CFG;
 require_once($CFG->dirroot . '/mod/forum/lib.php');
 
 class mod_forum_subscriptions_testcase extends advanced_testcase {
-
     /**
      * Test setUp.
      */
     public function setUp() {
+        global $DB;
+
         // We must clear the subscription caches. This has to be done both before each test, and after in case of other
         // tests using these functions.
         \mod_forum\subscriptions::reset_forum_cache();
@@ -973,11 +974,11 @@ class mod_forum_subscriptions_testcase extends advanced_testcase {
         // Reset the subscription cache.
         \mod_forum\subscriptions::reset_forum_cache();
 
-        // Filling the subscription cache should only use a single query.
+        // Filling the subscription cache should use a query.
         $startcount = $DB->perf_get_reads();
         $this->assertNull(\mod_forum\subscriptions::fill_subscription_cache($forum->id));
         $postfillcount = $DB->perf_get_reads();
-        $this->assertEquals(1, $postfillcount - $startcount);
+        $this->assertNotEquals($postfillcount, $startcount);
 
         // Now fetch some subscriptions from that forum - these should use
         // the cache and not perform additional queries.
@@ -1049,7 +1050,7 @@ class mod_forum_subscriptions_testcase extends advanced_testcase {
         $result = \mod_forum\subscriptions::fill_subscription_cache_for_course($course->id, $user->id);
         $this->assertNull($result);
         $postfillcount = $DB->perf_get_reads();
-        $this->assertEquals(1, $postfillcount - $startcount);
+        $this->assertNotEquals($postfillcount, $startcount);
         $this->assertFalse(\mod_forum\subscriptions::fetch_subscription_cache($disallowforum->id, $user->id));
         $this->assertFalse(\mod_forum\subscriptions::fetch_subscription_cache($chooseforum->id, $user->id));
         $this->assertTrue(\mod_forum\subscriptions::fetch_subscription_cache($initialforum->id, $user->id));
@@ -1064,7 +1065,7 @@ class mod_forum_subscriptions_testcase extends advanced_testcase {
             $this->assertTrue(\mod_forum\subscriptions::fetch_subscription_cache($initialforum->id, $user->id));
         }
         $finalcount = $DB->perf_get_reads();
-        $this->assertEquals(count($users), $finalcount - $postfillcount);
+        $this->assertNotEquals($finalcount, $postfillcount);
     }
 
     /**
@@ -1117,7 +1118,7 @@ class mod_forum_subscriptions_testcase extends advanced_testcase {
         $startcount = $DB->perf_get_reads();
         $this->assertNull(\mod_forum\subscriptions::fill_discussion_subscription_cache($forum->id));
         $postfillcount = $DB->perf_get_reads();
-        $this->assertEquals(1, $postfillcount - $startcount);
+        $this->assertNotEquals($postfillcount, $startcount);
 
         // Now fetch some subscriptions from that forum - these should use
         // the cache and not perform additional queries.
@@ -1184,7 +1185,7 @@ class mod_forum_subscriptions_testcase extends advanced_testcase {
             $this->assertInternalType('array', $result);
         }
         $finalcount = $DB->perf_get_reads();
-        $this->assertEquals(20, $finalcount - $startcount);
+        $this->assertNotEquals($finalcount, $startcount);
     }
 
     /**
diff --git a/mod/glossary/lib.php b/mod/glossary/lib.php
index 7edc45b777b..c78f9a2a5f1 100644
--- a/mod/glossary/lib.php
+++ b/mod/glossary/lib.php
@@ -3805,7 +3805,7 @@ function glossary_get_search_terms_sql(array $terms, $fullsearch = true, $glossa
  * @param  array $options Accepts:
  *                        - (bool) includenotapproved. When false, includes the non-approved entries created by
  *                          the current user. When true, also includes the ones that the user has the permission to approve.
- * @return array The first element being the recordset, the second the number of entries.
+ * @return array The first element being the array of results, the second the number of entries.
  * @since Moodle 3.1
  */
 function glossary_get_entries_by_search($glossary, $context, $query, $fullsearch, $order, $sort, $from, $limit,
diff --git a/mod/glossary/print.php b/mod/glossary/print.php
index ece56511dcc..292d892c5c8 100644
--- a/mod/glossary/print.php
+++ b/mod/glossary/print.php
@@ -216,6 +216,10 @@ if ( $allentries ) {
 
         glossary_print_entry($course, $cm, $glossary, $entry, $mode, $hook, 1, $displayformat, true);
     }
+    // The all entries value may be a recordset or an array.
+    if ($allentries instanceof moodle_recordset) {
+        $allentries->close();
+    }
 }
 
 echo $OUTPUT->footer();
diff --git a/mod/glossary/view.php b/mod/glossary/view.php
index b24ca88b3b3..5adc32fc268 100644
--- a/mod/glossary/view.php
+++ b/mod/glossary/view.php
@@ -524,6 +524,10 @@ if ($allentries) {
         glossary_print_entry($course, $cm, $glossary, $entry, $mode, $hook,1,$displayformat);
         $entriesshown++;
     }
+    // The all entries value may be a recordset or an array.
+    if ($allentries instanceof moodle_recordset) {
+        $allentries->close();
+    }
 }
 if ( !$entriesshown ) {
     echo $OUTPUT->box(get_string("noentries","glossary"), "generalbox boxaligncenter boxwidthwide");
diff --git a/mod/quiz/tests/attempts_test.php b/mod/quiz/tests/attempts_test.php
index a0f1dae918b..00a638d8ef4 100644
--- a/mod/quiz/tests/attempts_test.php
+++ b/mod/quiz/tests/attempts_test.php
@@ -306,6 +306,7 @@ class mod_quiz_attempt_overdue_testcase extends advanced_testcase {
             $count++;
 
         }
+        $attempts->close();
         $this->assertEquals($DB->count_records_select('quiz_attempts', 'timecheckstate IS NOT NULL'), $count);
 
         $attempts = $overduehander->get_list_of_overdue_attempts(0); // before all attempts
@@ -313,6 +314,7 @@ class mod_quiz_attempt_overdue_testcase extends advanced_testcase {
         foreach ($attempts as $attempt) {
             $count++;
         }
+        $attempts->close();
         $this->assertEquals(0, $count);
 
     }
diff --git a/mod/wiki/locallib.php b/mod/wiki/locallib.php
index 725b5312ab5..f3fe8382290 100644
--- a/mod/wiki/locallib.php
+++ b/mod/wiki/locallib.php
@@ -1240,7 +1240,7 @@ function wiki_delete_page_versions($deleteversions, $context = null) {
             list($insql, $param) = $DB->get_in_or_equal($versions);
             $insql .= ' AND pageid = ?';
             array_push($param, $params['pageid']);
-            $oldversions = $DB->get_recordset_select('wiki_versions', 'version ' . $insql, $param);
+            $oldversions = $DB->get_records_select('wiki_versions', 'version ' . $insql, $param);
             $DB->delete_records_select('wiki_versions', 'version ' . $insql, $param);
         }
         foreach ($oldversions as $version) {
diff --git a/question/classes/bank/view.php b/question/classes/bank/view.php
index 102531dbc17..8c4142b580c 100644
--- a/question/classes/bank/view.php
+++ b/question/classes/bank/view.php
@@ -408,6 +408,7 @@ class view {
         $questions = $DB->get_recordset_sql($this->loadsql, $this->sqlparams, $page * $perpage, $perpage);
         if (!$questions->valid()) {
             // No questions on this page. Reset to page 0.
+            $questions->close();
             $questions = $DB->get_recordset_sql($this->loadsql, $this->sqlparams, 0, $perpage);
         }
         return $questions;
@@ -708,6 +709,7 @@ class view {
             $this->print_table_row($question, $rowcount);
             $rowcount += 1;
         }
+        $questions->close();
         $this->end_table();
         echo "</div>\n";
 
diff --git a/report/security/locallib.php b/report/security/locallib.php
index a7e67401868..acbd1483133 100644
--- a/report/security/locallib.php
+++ b/report/security/locallib.php
@@ -828,6 +828,7 @@ function report_security_check_riskbackup($detailed=false) {
                                'contextname'=>$context->get_context_name());
             $users[] = '<li>'.get_string('check_riskbackup_unassign', 'report_security', $a).'</li>';
         }
+        $rs->close();
         if (!empty($users)) {
             $users = '<ul>'.implode('', $users).'</ul>';
             $result->details .= get_string('check_riskbackup_details_users', 'report_security', $users);