Ticket #8958: reduce_attach_query.8958.diff

wp-includes/rewrite.php

@@ -794 +794 @@
 
                 if ( !$posts )
                         return array( array(), array() );
-
+                
+                // get the set of posts with an attachment to reduce the number of queries inside the loop
+                $all_attachments = $wpdb->get_results( "SELECT post_parent FROM $wpdb->posts WHERE post_type = 'attachment'" );
+                
                 foreach ($posts as $id => $post) {
+                                
                         // URL => page name
                         $uri = get_page_uri($id);
-                        $attachments = $wpdb->get_results( $wpdb->prepare( "SELECT ID, post_name, post_parent FROM $wpdb->posts WHERE post_type = 'attachment' AND post_parent = %d", $id ));
-                        if ( $attachments ) {
-                                foreach ( $attachments as $attachment ) {
-                                        $attach_uri = get_page_uri($attachment->ID);
-                                        $page_attachment_uris[$attach_uri] = $attachment->ID;
+                        if (in_array( $id, $all_attachments )) {
+                                $attachments = $wpdb->get_results( $wpdb->prepare( "SELECT ID, post_name, post_parent FROM $wpdb->posts WHERE post_type = 'attachment' AND post_parent = %d", $id ));
+                                if ( $attachments ) {
+                                        foreach ( $attachments as $attachment ) {
+                                                $attach_uri = get_page_uri($attachment->ID);
+                                                $page_attachment_uris[$attach_uri] = $attachment->ID;
+                                        }
                                 }
                         }