Date: Tue, 25 Dec 2018 09:45:45 +0900
From: Michael Paquier <michael@paquier.xyz>
To: digoal@126.com, pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #15565: truncate bug with tables which have temp table
 inherited
Message-ID: <20181225004545.GB2334@paquier.xyz>
References: <15565-ce67a48d0244436a@postgresql.org>
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On Mon, Dec 24, 2018 at 09:17:46AM +0000, PG Bug reporting form wrote:
> create table public.a (id int);
> create temp table a (like public.a) inherits(public.a);

This issue is way older than 11.

A couple of months ago there has been a discussion about mixing
temporary and permanent tables in a partition tree:
https://www.postgresql.org/message-id/CAKJS1f94Ojk0og9GMkRHGt8wHTW=ijq5KzJKuoBoqWLwSVwGmw@mail.gmail.com

The conclusion of this time was that we don't want to allow mixing
relations with different persistencies in the same tree for
partitions because those rely on relation cache lookups for their
description (PartitionDesc), however inheritance trees have been able
to accidently work this way for a long time.  This shares a little bit
of history with this report as partition trees and inheritance share
the same lookups at pg_inherits.

So there could be an argument to restrict the definition of
inheritance trees with trees mixing relation persistencies.

It is hard to say as well that truncate silently bypasses the
truncation of a temporary relation from another session if a given
session wants to truncate a whole tree.

Another approach would be to just live with this issue, as the use
case is pretty narrow anyway.
--
Michael

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