Horton

Re: Assert failure due to "drop schema pg_temp_3 cascade" for temporary tables and \d+ is not showing any info after drooping temp table schema

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Michael Paquier <michael@paquier.xyz>, Mahendra Singh <mahi6run@gmail.com>, Kyotaro Horiguchi <horikyota.ntt@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2020-01-06T17:33:47Z
Lists: pgsql-bugs, pgsql-hackers 
Robert Haas <robertmhaas@gmail.com> writes:
> I'm not arguing for a revert of 246a6c8.  I think we should just change this:
> ...
> To look more like:

> char *nspname = get_namespace_name(classForm->relnamespace);
> if (nspname != NULL)
>    ereport(..."autovacuum: dropping orphan temp table \"%s.%s.%s\"...)
> else
>    ereport(..."autovacuum: dropping orphan temp table with OID %u"....)

> If we do that, then I think we can just revert
> a052f6cbb84e5630d50b68586cecc127e64be639 completely.

+1 to both of those --- although I think we could still provide the
table name in the null-nspname case.

> autovacuum.c seems to have been using get_namespace_name() without a
> null check since 2006, so it's not really the fault of your patch as I
> had originally thought. I wonder how in the world we've managed to get
> away with it for as long as we have.

Maybe we haven't.  It's not clear that infrequent autovac crashes would
get reported to us, or that we'd successfully find the cause if they were.

I think what you propose above is a back-patchable bug fix.

			regards, tom lane

Commits

  1. Avoid failure if autovacuum tries to access a just-dropped temp namespace.

  2. Revert "Forbid DROP SCHEMA on temporary namespaces"

  3. Forbid DROP SCHEMA on temporary namespaces

  4. Make autovacuum more aggressive to remove orphaned temp tables

  5. Code review for early drop of orphaned temp relations in autovacuum.