Re: Global temporary tables

From: Dean Rasheed <dean(dot)a(dot)rasheed(at)gmail(dot)com>
To: Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>
Cc: Kirk Wolak <wolakk(at)gmail(dot)com>, Andrew Dunstan <andrew(at)dunslane(dot)net>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: Global temporary tables
Date: 2026-06-30 20:21:27
Message-ID: CAEZATCUSAQB3zRiycD=-xFXg-2rPRv9BtL6kFu3BsSwBnTWyoA@mail.gmail.com
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On Tue, 30 Jun 2026 at 20:29, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> wrote:
>
> I am testing this patchset. Generally, it looks very well. I didn't see any bloat on catalog
>
> I found an issue - TRUNCATE waits when gtt is used by different transactions, and TRUNCATE removes content in all sessions.
>
> Is it expected?

Thanks for testing!

The waiting issue for TRUNCATE is interesting. I hadn't considered
that at all, so TRUNCATE on a global temporary table still takes an
access exclusive lock, like any other table, but I guess that's not
necessary. I wonder what lock level we could reduce it to.

I can't reproduce TRUNCATE removing content in all sessions, but
that's definitely not supposed to happen. Can you share what you did
to cause that?

Regards,
Dean

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