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: Michael Paquier <michael@paquier.xyz>
Cc: Mahendra Singh Thalor <mahi6run@gmail.com>, Robert Haas <robertmhaas@gmail.com>, Kyotaro Horiguchi <horikyota.ntt@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2020-02-28T18:45:29Z
Lists: pgsql-bugs, pgsql-hackers

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I wrote:
> Also, I notice that isTempNamespaceInUse is already detecting the case
> where the namespace doesn't exist or isn't really a temp namespace.
> I wonder whether it'd be better to teach that to return an indicator about
> the namespace not being what you think it is.  That would force us to look
> at its other callers to see if any of them have related bugs, which seems
> like a good thing to check --- and even if they don't, having to think
> about the point in future call sites might forestall new bugs.

After poking around, I see there aren't any other callers.  But I think
that the cause of this bug is clearly failure to think carefully about
the different cases that isTempNamespaceInUse is recognizing, so that
the right way to fix it is more like the attached.

In the back branches, we could leave isTempNamespaceInUse() in place
but unused, just in case somebody is calling it.  I kind of doubt that
anyone is, given the small usage in core, but maybe.

			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.