API: Force straight join for prop=linkshere|transcludedin|fileusage

MySQL (or at least 5.5.5-10.0.23-MariaDB) chooses a really bad query plan if it
thinks there will be more matching rows in the linktable than are in page. Use
STRAIGHT_JOIN here to force it to use the intended, fast plan. See T145079 for
details.

Bug: T145079
Change-Id: I1a363450b818a049938145d0feb207c9894d2a49

diff --git a/includes/api/ApiQueryBacklinksprop.php b/includes/api/ApiQueryBacklinksprop.php
index 236fb9e..8e89c32 100644 (file)
--- a/includes/api/ApiQueryBacklinksprop.php
+++ b/includes/api/ApiQueryBacklinksprop.php
@@ -264,6 +264,12 @@ class ApiQueryBacklinksprop extends ApiQueryGeneratorBase {
                        }
                }
 
+               // MySQL (or at least 5.5.5-10.0.23-MariaDB) chooses a really bad query
+               // plan if it thinks there will be more matching rows in the linktable
+               // than are in page. Use STRAIGHT_JOIN here to force it to use the
+               // intended, fast plan. See T145079 for details.
+               $this->addOption( 'STRAIGHT_JOIN' );
+
                $this->addOption( 'LIMIT', $params['limit'] + 1 );
 
                $res = $this->select( __METHOD__ );