db_exec_plsql's been hacked to execute a "select" directly, discarding the result. Multi-statement blocks are currently dumped into a temp function, executed, with the temp function then being dropped. We haven't quite decided what we'll do to improve performance for this latter case (cache the function name and only create it once?) but it works for now.
So you should leave the db_exec_plsql alone, amd change the query in your *-postgresql.xql file to read "select activity__set_attrs(...)".
