Removed RC query UNION

* MySQL is smart enough that this is no longer needed

Change-Id: If173cdc53599cd02068ce2480ab667c5f9e69b76

diff --git a/includes/specials/SpecialRecentchanges.php b/includes/specials/SpecialRecentchanges.php
index a408beb..60cdb0e 100644 (file)
--- a/includes/specials/SpecialRecentchanges.php
+++ b/includes/specials/SpecialRecentchanges.php
@@ -424,59 +424,16 @@ class SpecialRecentChanges extends IncludableSpecialPage {
                        return false;
                }
 
-               // Don't use the new_namespace_time timestamp index if:
-               // (a) "All namespaces" selected
-               // (b) We want pages in more than one namespace (inverted/associated)
-               // (c) There is a tag to filter on (use tag index instead)
-               // (d) UNION + sort/limit is not an option for the DBMS
-               if ( $namespace === ''
-                       || ( $invert || $associated )
-                       || $opts['tagfilter'] != ''
-                       || !$dbr->unionSupportsOrderAndLimit()
-               ) {
-                       $res = $dbr->select( $tables, $fields, $conds, __METHOD__,
-                               array( 'ORDER BY' => 'rc_timestamp DESC', 'LIMIT' => $limit ) +
-                                       $query_options,
-                               $join_conds );
-               } else {
-                       // We have a new_namespace_time index! UNION over new=(0,1) and sort result set!
-
-                       // New pages
-                       $sqlNew = $dbr->selectSQLText(
-                               $tables,
-                               $fields,
-                               array( 'rc_new' => 1 ) + $conds,
-                               __METHOD__,
-                               array(
-                                       'ORDER BY' => 'rc_timestamp DESC',
-                                       'LIMIT' => $limit,
-                                       'USE INDEX' => array( 'recentchanges' => 'new_name_timestamp' )
-                               ),
-                               $join_conds
-                       );
-
-                       // Old pages
-                       $sqlOld = $dbr->selectSQLText(
-                               $tables,
-                               $fields,
-                               array( 'rc_new' => 0 ) + $conds,
-                               __METHOD__,
-                               array(
-                                       'ORDER BY' => 'rc_timestamp DESC',
-                                       'LIMIT' => $limit,
-                                       'USE INDEX' => array( 'recentchanges' => 'new_name_timestamp' )
-                               ),
-                               $join_conds
-                       );
-
-                       # Join the two fast queries, and sort the result set
-                       $sql = $dbr->unionQueries( array( $sqlNew, $sqlOld ), false ) .
-                               ' ORDER BY rc_timestamp DESC';
-                       $sql = $dbr->limitResult( $sql, $limit, false );
-                       $res = $dbr->query( $sql, __METHOD__ );
-               }
-
-               return $res;
+               // rc_new is not an ENUM, but adding a redundant rc_new IN (0,1) gives mysql enough
+               // knowledge to use an index merge if it wants (it may use some other index though).
+               return $dbr->select(
+                       $tables,
+                       $fields,
+                       $conds + array( 'rc_new' => array( 0, 1 ) ),
+                       __METHOD__,
+                       array( 'ORDER BY' => 'rc_timestamp DESC', 'LIMIT' => $limit ) + $query_options,
+                       $join_conds
+               );
        }
 
        /**