Changed FOR UPDATE handling in Postgresql

Postgresql cannot handle FOR UPDATE with outer joins, but it allows
specifying which tables can be locked. This changes DatabasePostgresql
to render proper FOR UPDATE statements that only include the main
table and any tables in inner joins.

Bug: 47055
Change-Id: I1ac587ac39f448b9e7f4befb44826b43044ad6f0

diff --git a/includes/db/DatabasePostgres.php b/includes/db/DatabasePostgres.php
index cfa2074..edc8b27 100644 (file)
--- a/includes/db/DatabasePostgres.php
+++ b/includes/db/DatabasePostgres.php
@@ -772,6 +772,29 @@ __INDEXATTR__;
                return false;
        }
 
+       /**
+        * Change the FOR UPDATE option as necessary based on the join conditions. Then pass
+        * to the parent function to get the actual SQL text.
+        *
+        * In Postgres when using FOR UPDATE, only the main table and tables that are inner joined
+        * can be locked. That means tables in an outer join cannot be FOR UPDATE locked. Trying to do
+        * so causes a DB error. This wrapper checks which tables can be locked and adjusts it accordingly.
+        */
+       function selectSQLText( $table, $vars, $conds = '', $fname = __METHOD__, $options = array(), $join_conds = array() ) {
+               $forUpdateKey = array_search( 'FOR UPDATE', $options );
+               if ( $forUpdateKey !== false && $join_conds ) {
+                       unset( $options[$forUpdateKey] );
+
+                       foreach ( $join_conds as $table => $join_cond ) {
+                               if ( 0 === preg_match( '/^(?:LEFT|RIGHT|FULL)(?: OUTER)? JOIN$/i', $join_cond[0] ) ) {
+                                       $options['FOR UPDATE'][] = $table;
+                               }
+                       }
+               }
+
+               return parent::selectSQLText( $table, $vars, $conds, $fname, $options, $join_conds );
+       }
+
        /**
         * INSERT wrapper, inserts an array into a table
         *
@@ -1473,9 +1496,12 @@ SQL;
                //              : false );
                //}
 
-               if ( isset( $noKeyOptions['FOR UPDATE'] ) ) {
+               if ( isset( $options['FOR UPDATE'] ) ) {
+                       $postLimitTail .= ' FOR UPDATE OF ' . implode( ', ', $options['FOR UPDATE'] );
+               } else if ( isset( $noKeyOptions['FOR UPDATE'] ) ) {
                        $postLimitTail .= ' FOR UPDATE';
                }
+
                if ( isset( $noKeyOptions['DISTINCT'] ) || isset( $noKeyOptions['DISTINCTROW'] ) ) {
                        $startOpts .= 'DISTINCT';
                }