Re: Locks on temp table and PREPARE

Emmanuel Cecchet <manu@frogthinker.org> writes:
> Take PG 8.3.0 and try:
> BEGIN;
> CREATE TEMP TABLE foo (x int) ON COMMIT DROP;
> PREPARE TRANSACTION 't1';
> [BEGIN;] <-- doesn't really matter if you start a new transaction or not
> CREATE TEMP TABLE foo (x int); <-- blocks until t1 commits

> I have been tracking down the problem and it looks like 
> PostPrepare_Locks is holding the locks on 'foo' for some reason I don't 
> really get.

AFAIK that doesn't really have anything to do with the temp-ness of the
table; it'd be the same with a regular table.  The problem is you have
an in-doubt tuple in pg_class for pg_temp_NNN.foo, and you are trying
to create another one for the same schema/relname, and so the unique
index check is blocking to see what happens to the other transaction
that's creating/deleting the conflicting tuple.
        regards, tom lane