Merge "ApiQueryDeletedRevisions: Optimize ascending title generation"

diff --combined includes/api/ApiQueryAllDeletedRevisions.php
index 0da9436,f802c95..172ee99
--- 1/includes/api/ApiQueryAllDeletedRevisions.php
--- 2/includes/api/ApiQueryAllDeletedRevisions.php
+++ b/includes/api/ApiQueryAllDeletedRevisions.php
@@@ -55,6 -55,7 +55,6 @@@ class ApiQueryAllDeletedRevisions exten
  
                $result = $this->getResult();
                $pageSet = $this->getPageSet();
 -              $titles = $pageSet->getTitles();
  
                // This module operates in two modes:
                // 'user': List deleted revs by a certain user
@@@ -82,6 -83,21 +82,21 @@@
                        }
                }
  
+               // If we're generating titles only, we can use DISTINCT for a better
+               // query. But we can't do that in 'user' mode (wrong index), and we can
+               // only do it when sorting ASC (because MySQL apparently can't use an
+               // index backwards for grouping even though it can for ORDER BY, WTF?)
+               $dir = $params['dir'];
+               $optimizeGenerateTitles = false;
+               if ( $mode === 'all' && $params['generatetitles'] && $resultPageSet !== null ) {
+                       if ( $dir === 'newer' ) {
+                               $optimizeGenerateTitles = true;
+                       } else {
+                               $p = $this->getModulePrefix();
+                               $this->setWarning( "For better performance when generating titles, set {$p}dir=newer" );
+                       }
+               }
+ 
                $this->addTables( 'archive' );
                if ( $resultPageSet === null ) {
                        $this->parseParameters( $params );
@@@ -89,7 -105,12 +104,12 @@@
                        $this->addFields( array( 'ar_title', 'ar_namespace' ) );
                } else {
                        $this->limit = $this->getParameter( 'limit' ) ?: 10;
-                       $this->addFields( array( 'ar_title', 'ar_namespace', 'ar_timestamp', 'ar_rev_id', 'ar_id' ) );
+                       $this->addFields( array( 'ar_title', 'ar_namespace' ) );
+                       if ( $optimizeGenerateTitles ) {
+                               $this->addOption( 'DISTINCT' );
+                       } else {
+                               $this->addFields( array( 'ar_timestamp', 'ar_rev_id', 'ar_id' ) );
+                       }
                }
  
                if ( $this->fld_tags ) {
@@@ -129,7 -150,6 +149,6 @@@
                        }
                }
  
-               $dir = $params['dir'];
                $miser_ns = null;
  
                if ( $mode == 'all' ) {
@@@ -228,7 -248,14 +247,14 @@@
                if ( !is_null( $params['continue'] ) ) {
                        $cont = explode( '|', $params['continue'] );
                        $op = ( $dir == 'newer' ? '>' : '<' );
-                       if ( $mode == 'all' ) {
+                       if ( $optimizeGenerateTitles ) {
+                               $this->dieContinueUsageIf( count( $cont ) != 2 );
+                               $ns = intval( $cont[0] );
+                               $this->dieContinueUsageIf( strval( $ns ) !== $cont[0] );
+                               $title = $db->addQuotes( $cont[1] );
+                               $this->addWhere( "ar_namespace $op $ns OR " .
+                                       "(ar_namespace = $ns AND ar_title $op= $title)" );
+                       } elseif ( $mode == 'all' ) {
                                $this->dieContinueUsageIf( count( $cont ) != 4 );
                                $ns = intval( $cont[0] );
                                $this->dieContinueUsageIf( strval( $ns ) !== $cont[0] );
@@@ -258,7 -285,13 +284,13 @@@
  
                $sort = ( $dir == 'newer' ? '' : ' DESC' );
                $orderby = array();
-               if ( $mode == 'all' ) {
+               if ( $optimizeGenerateTitles ) {
+                       // Targeting index name_title_timestamp
+                       if ( $params['namespace'] === null || count( array_unique( $params['namespace'] ) ) > 1 ) {
+                               $orderby[] = "ar_namespace $sort";
+                       }
+                       $orderby[] = "ar_title $sort";
+               } elseif ( $mode == 'all' ) {
                        // Targeting index name_title_timestamp
                        if ( $params['namespace'] === null || count( array_unique( $params['namespace'] ) ) > 1 ) {
                                $orderby[] = "ar_namespace $sort";
@@@ -282,7 -315,9 +314,9 @@@
                foreach ( $res as $row ) {
                        if ( ++$count > $this->limit ) {
                                // We've had enough
-                               if ( $mode == 'all' ) {
+                               if ( $optimizeGenerateTitles ) {
+                                       $this->setContinueEnumParameter( 'continue', "$row->ar_namespace|$row->ar_title" );
+                               } elseif ( $mode == 'all' ) {
                                        $this->setContinueEnumParameter( 'continue',
                                                "$row->ar_namespace|$row->ar_title|$row->ar_timestamp|$row->ar_id"
                                        );