+
+ // Note that the update conditions do not rely on atomicity of the
+ // SELECT query in order to guarantee that all rows are updated. The
+ // results of the SELECT are merely a partitioning hint. Simultaneous
+ // updates merely result in the wrong number of rows being updated
+ // in a batch.
+
+ $res = $dbw->select( $table, $key, $selectConds, __METHOD__,
+ [ 'ORDER BY' => $key, 'LIMIT' => $batchSize ] );
+ if ( $res->numRows() ) {
+ $res->seek( $res->numRows() - 1 );
+ $row = $res->fetchObject();
+ $end = $dbw->addQuotes( $row->$key );
+ $selectConds = array_merge( $where, [ "$key > $end" ] );
+ $updateConds = array_merge( $where, [ "$key <= $end" ] );
+ } else {
+ $updateConds = $where;
+ }
+ if ( $prevEnd !== false ) {
+ $updateConds = array_merge( [ "$key > $prevEnd" ], $updateConds );
+ }
+
+ $query = "UPDATE " . $dbw->tableName( $table ) .
+ " SET " . $set .
+ " WHERE " . $dbw->makeList( $updateConds, IDatabase::LIST_AND );
+