backend/commands/command.c has a routine is_view() that tests for view-ness by scanning pg_rewrite (all of it) to see if the given relation has any ON SELECT rules. This is only used to disallow AlterTableAddConstraint and LockTableCommand on views. While I don't care much about the performance of AlterTableAddConstraint, it does bug me that this might slow down LOCK TABLE a good deal. Any objection to replacing this routine by a test for relkind = VIEW? regards, tom lane