diff --git a/cache/classes/definition.php b/cache/classes/definition.php
index 6b4f47b6905..1d5a53222b3 100644
--- a/cache/classes/definition.php
+++ b/cache/classes/definition.php
@@ -242,7 +242,8 @@ class cache_definition {
     protected $datasourcefile = null;
 
     /**
-     * The data source class aggregate to use. This is a super advanced setting.
+     * Deprecated - this is completely unused.
+     * @deprecated since 2.7.4
      * @var string
      */
     protected $datasourceaggregate = null;
@@ -324,11 +325,11 @@ class cache_definition {
      *
      * @param string $id
      * @param array $definition
-     * @param string $datasourceaggregate
+     * @param string $unused Used to be datasourceaggregate but that was removed and this is now unused.
      * @return cache_definition
      * @throws coding_exception
      */
-    public static function load($id, array $definition, $datasourceaggregate = null) {
+    public static function load($id, array $definition, $unused = null) {
         global $CFG;
 
         if (!array_key_exists('mode', $definition)) {
@@ -520,7 +521,6 @@ class cache_definition {
         $cachedefinition->overrideclassfile = $overrideclassfile;
         $cachedefinition->datasource = $datasource;
         $cachedefinition->datasourcefile = $datasourcefile;
-        $cachedefinition->datasourceaggregate = $datasourceaggregate;
         $cachedefinition->staticacceleration = $staticacceleration;
         $cachedefinition->staticaccelerationsize = $staticaccelerationsize;
         $cachedefinition->ttl = $ttl;
diff --git a/cache/classes/factory.php b/cache/classes/factory.php
index 825a44102ed..72c47b5b555 100644
--- a/cache/classes/factory.php
+++ b/cache/classes/factory.php
@@ -178,17 +178,17 @@ class cache_factory {
      * @param string $component
      * @param string $area
      * @param array $identifiers
-     * @param string $aggregate
+     * @param string $unused Used to be data source aggregate however that was removed and this is now unused.
      * @return cache_application|cache_session|cache_request
      */
-    public function create_cache_from_definition($component, $area, array $identifiers = array(), $aggregate = null) {
+    public function create_cache_from_definition($component, $area, array $identifiers = array(), $unused = null) {
         $definitionname = $component.'/'.$area;
         if (isset($this->cachesfromdefinitions[$definitionname])) {
             $cache = $this->cachesfromdefinitions[$definitionname];
             $cache->set_identifiers($identifiers);
             return $cache;
         }
-        $definition = $this->create_definition($component, $area, $aggregate);
+        $definition = $this->create_definition($component, $area);
         $definition->set_identifiers($identifiers);
         $cache = $this->create_cache($definition, $identifiers);
         // Loaders are always held onto to speed up subsequent requests.
@@ -379,14 +379,13 @@ class cache_factory {
      * Creates a definition instance or returns the existing one if it has already been created.
      * @param string $component
      * @param string $area
-     * @param string $aggregate
+     * @param string $unused This used to be data source aggregate - however that functionality has been removed and
+     *        this argument is now unused.
      * @return cache_definition
+     * @throws coding_exception If the definition cannot be found.
      */
-    public function create_definition($component, $area, $aggregate = null) {
+    public function create_definition($component, $area, $unused = null) {
         $id = $component.'/'.$area;
-        if ($aggregate) {
-            $id .= '::'.$aggregate;
-        }
         if (!isset($this->definitions[$id])) {
             // This is the first time this definition has been requested.
             if ($this->is_initialising()) {
@@ -408,13 +407,6 @@ class cache_factory {
                         // To serve this purpose and avoid errors we are going to make use of an ad-hoc cache rather than
                         // search for the definition which would possibly cause an infitite loop trying to initialise the cache.
                         $definition = cache_definition::load_adhoc(cache_store::MODE_REQUEST, $component, $area);
-                        if ($aggregate !== null) {
-                            // If you get here you deserve a warning. We have to use an ad-hoc cache here, so we can't find the definition and therefor
-                            // can't find any information about the datasource or any of its aggregated.
-                            // Best of luck.
-                            debugging('An unknown cache was requested during development with an aggregate that could not be loaded. Ad-hoc cache used instead.', DEBUG_DEVELOPER);
-                            $aggregate = null;
-                        }
                     } else {
                         // Either a typo of the developer has just created the definition and is using it for the first time.
                         $this->reset();
@@ -427,10 +419,10 @@ class cache_factory {
                             debugging('Cache definitions reparsed causing cache reset in order to locate definition.
                                 You should bump the version number to ensure definitions are reprocessed.', DEBUG_DEVELOPER);
                         }
-                        $definition = cache_definition::load($id, $definition, $aggregate);
+                        $definition = cache_definition::load($id, $definition);
                     }
                 } else {
-                    $definition = cache_definition::load($id, $definition, $aggregate);
+                    $definition = cache_definition::load($id, $definition);
                 }
             }
             $this->definitions[$id] = $definition;
diff --git a/cache/classes/helper.php b/cache/classes/helper.php
index dd150b7c403..4f0586b382c 100644
--- a/cache/classes/helper.php
+++ b/cache/classes/helper.php
@@ -280,13 +280,6 @@ class cache_helper {
     /**
      * Purges the cache for a specific definition.
      *
-     * If you need to purge a definition that requires identifiers or an aggregate and you don't
-     * know the details of those please use cache_helper::purge_stores_used_by_definition instead.
-     * It is a more aggressive purge and will purge all data within the store, not just the data
-     * belonging to the given definition.
-     *
-     * @todo MDL-36660: Change the signature: $aggregate must be added.
-     *
      * @param string $component
      * @param string $area
      * @param array $identifiers
@@ -298,7 +291,6 @@ class cache_helper {
         // Initialise, in case of a store.
         if ($cache instanceof cache_store) {
             $factory = cache_factory::instance();
-            // TODO MDL-36660: Providing $aggregate is required for purging purposes: $definition->get_id()
             $definition = $factory->create_definition($component, $area, null);
             $definition->set_identifiers($identifiers);
             $cache->initialise($definition);
diff --git a/cache/classes/loaders.php b/cache/classes/loaders.php
index ae2ba70bd82..6cd588a273e 100644
--- a/cache/classes/loaders.php
+++ b/cache/classes/loaders.php
@@ -166,12 +166,12 @@ class cache implements cache_loader {
      * @param string $component The component for the definition
      * @param string $area The area for the definition
      * @param array $identifiers Any additional identifiers that should be provided to the definition.
-     * @param string $aggregate Super advanced feature. More docs later.
+     * @param string $unused Used to be datasourceaggregate but that was removed and this is now unused.
      * @return cache_application|cache_session|cache_store
      */
-    public static function make($component, $area, array $identifiers = array(), $aggregate = null) {
+    public static function make($component, $area, array $identifiers = array(), $unused = null) {
         $factory = cache_factory::instance();
-        return $factory->create_cache_from_definition($component, $area, $identifiers, $aggregate);
+        return $factory->create_cache_from_definition($component, $area, $identifiers);
     }
 
     /**
diff --git a/cache/disabledlib.php b/cache/disabledlib.php
index 26c938b821d..fae2f357c83 100644
--- a/cache/disabledlib.php
+++ b/cache/disabledlib.php
@@ -184,10 +184,10 @@ class cache_factory_disabled extends cache_factory {
      *
      * @param string $component
      * @param string $area
-     * @param string $aggregate Unused.
+     * @param string $unused Used to be datasourceaggregate but that was removed and this is now unused.
      * @return cache_definition
      */
-    public function create_definition($component, $area, $aggregate = null) {
+    public function create_definition($component, $area, $unused = null) {
         return cache_definition::load_adhoc(cache_store::MODE_REQUEST, $component, $area);
     }
 
@@ -208,11 +208,11 @@ class cache_factory_disabled extends cache_factory {
      * @param string $component
      * @param string $area
      * @param array $identifiers
-     * @param string $aggregate
+     * @param string $unused Used to be datasourceaggregate but that was removed and this is now unused.
      * @return cache_application|cache_session|cache_request
      */
-    public function create_cache_from_definition($component, $area, array $identifiers = array(), $aggregate = null) {
-        $definition = $this->create_definition($component, $area, $aggregate);
+    public function create_cache_from_definition($component, $area, array $identifiers = array(), $unused = null) {
+        $definition = $this->create_definition($component, $area);
         $cache = $this->create_cache($definition, $identifiers);
         return $cache;
     }
diff --git a/cache/upgrade.txt b/cache/upgrade.txt
index 75ce1e69eb5..22ffed49b80 100644
--- a/cache/upgrade.txt
+++ b/cache/upgrade.txt
@@ -1,6 +1,16 @@
 This files describes API changes in /cache/stores/* - cache store plugins.
 Information provided here is intended especially for developers.
 
+=== 2.7.4 ===
+* Cache data source aggregation functionality has been removed. This functionality was found to be broken and unused.
+  It was decided that rather than fixing it it should be removed.
+  As well as the processing code being removed the following API changes have been made.
+  The following changes have come about because of it:
+   - cache_definition::$datasourceaggregate is deprecated an unused.
+   - cache_definition::load Argument 3 (final arg) is now unused.
+   - cache_factory::create_cache_from_definition Argument 4 (final arg) is now unused.
+   - cache::make Argument 4 (final arg) is now unused.
+
 === 2.7 ===
 * cache_store::is_ready is no longer abstract, calling cache_store::are_requirements_met by default.
 
@@ -22,4 +32,4 @@ Information provided here is intended especially for developers.
 * cleanup method renamed to instance_deleted.
   It is now called when the store is deleted as all comments suggested anyway.
 * instance_created method added.
-  It is called when the store is created for the very first time.
\ No newline at end of file
+  It is called when the store is created for the very first time.