Merge "RCFilters: Filter duplicates when filtering for multiple tags"

[lhc/web/wiklou.git] / includes / specials / SpecialRecentchanges.php

diff --git a/includes/specials/SpecialRecentchanges.php b/includes/specials/SpecialRecentchanges.php
index a05900b..852bfa4 100644 (file)
--- a/includes/specials/SpecialRecentchanges.php
+++ b/includes/specials/SpecialRecentchanges.php
@@ -429,13 +429,14 @@ class SpecialRecentChanges extends ChangesListSpecialPage {
                $fields[] = 'page_latest';
                $join_conds['page'] = [ 'LEFT JOIN', 'rc_cur_id=page_id' ];
 
+               $tagFilter = explode( '|', $opts['tagfilter'] );
                ChangeTags::modifyDisplayQuery(
                        $tables,
                        $fields,
                        $conds,
                        $join_conds,
                        $query_options,
-                       $opts['tagfilter']
+                       $tagFilter
                );
 
                if ( !$this->runMainQueryHook( $tables, $fields, $conds, $query_options, $join_conds,
@@ -448,13 +449,24 @@ class SpecialRecentChanges extends ChangesListSpecialPage {
                        return false;
                }
 
+               $orderByAndLimit = [
+                       'ORDER BY' => 'rc_timestamp DESC',
+                       'LIMIT' => $opts['limit']
+               ];
+               if ( in_array( 'DISTINCT', $query_options ) ) {
+                       // ChangeTags::modifyDisplayQuery() adds DISTINCT when filtering on multiple tags.
+                       // In order to prevent DISTINCT from causing query performance problems,
+                       // we have to GROUP BY the primary key. This in turn requires us to add
+                       // the primary key to the end of the ORDER BY, and the old ORDER BY to the
+                       // start of the GROUP BY
+                       $orderByAndLimit['ORDER BY'] = 'rc_timestamp DESC, rc_id DESC';
+                       $orderByAndLimit['GROUP BY'] = 'rc_timestamp, rc_id';
+               }
                // array_merge() is used intentionally here so that hooks can, should
                // they so desire, override the ORDER BY / LIMIT condition(s); prior to
                // MediaWiki 1.26 this used to use the plus operator instead, which meant
                // that extensions weren't able to change these conditions
-               $query_options = array_merge( [
-                       'ORDER BY' => 'rc_timestamp DESC',
-                       'LIMIT' => $opts['limit'] ], $query_options );
+               $query_options = array_merge( $orderByAndLimit, $query_options );
                $rows = $dbr->select(
                        $tables,
                        $fields,