API: Force indexes for prop=linkshere|transcludedin|fileusage

MySQL's optimizer chokes if we have too many values in "$bl_title IN
(...)" and chooses the wrong index, so specify the correct index to use
for the query.

Bug: T139056
Change-Id: I989dfbe898b75d649c22e198a6fbdd3a2de196e5

diff --git a/includes/api/ApiQueryBacklinksprop.php b/includes/api/ApiQueryBacklinksprop.php
index 3810e90..236fb9e 100644 (file)
--- a/includes/api/ApiQueryBacklinksprop.php
+++ b/includes/api/ApiQueryBacklinksprop.php
@@ -53,6 +53,7 @@ class ApiQueryBacklinksprop extends ApiQueryGeneratorBase {
                        'code' => 'lh',
                        'prefix' => 'pl',
                        'linktable' => 'pagelinks',
+                       'indexes' => [ 'pl_namespace', 'pl_backlinks_namespace' ],
                        'from_namespace' => true,
                        'showredirects' => true,
                ],
@@ -60,6 +61,7 @@ class ApiQueryBacklinksprop extends ApiQueryGeneratorBase {
                        'code' => 'ti',
                        'prefix' => 'tl',
                        'linktable' => 'templatelinks',
+                       'indexes' => [ 'tl_namespace', 'tl_backlinks_namespace' ],
                        'from_namespace' => true,
                        'showredirects' => true,
                ],
@@ -67,6 +69,7 @@ class ApiQueryBacklinksprop extends ApiQueryGeneratorBase {
                        'code' => 'fu',
                        'prefix' => 'il',
                        'linktable' => 'imagelinks',
+                       'indexes' => [ 'il_to', 'il_backlinks_namespace' ],
                        'from_namespace' => true,
                        'to_namespace' => NS_FILE,
                        'exampletitle' => 'File:Example.jpg',
@@ -249,6 +252,18 @@ class ApiQueryBacklinksprop extends ApiQueryGeneratorBase {
                // Override any ORDER BY from above with what we calculated earlier.
                $this->addOption( 'ORDER BY', array_keys( $sortby ) );
 
+               // MySQL's optimizer chokes if we have too many values in "$bl_title IN
+               // (...)" and chooses the wrong index, so specify the correct index to
+               // use for the query. See T139056 for details.
+               if ( !empty( $settings['indexes'] ) ) {
+                       list( $idxNoFromNS, $idxWithFromNS ) = $settings['indexes'];
+                       if ( $params['namespace'] !== null && !empty( $settings['from_namespace'] ) ) {
+                               $this->addOption( 'USE INDEX', [ $settings['linktable'] => $idxWithFromNS ] );
+                       } else {
+                               $this->addOption( 'USE INDEX', [ $settings['linktable'] => $idxNoFromNS ] );
+                       }
+               }
+
                $this->addOption( 'LIMIT', $params['limit'] + 1 );
 
                $res = $this->select( __METHOD__ );