Re: DDL result is lost by CREATE DATABASE with WAL_LOG strategy

From: Nathan Bossart <nathandbossart(at)gmail(dot)com>
To: Michael Paquier <michael(at)paquier(dot)xyz>
Cc: Dilip Kumar <dilipbalaut(at)gmail(dot)com>, "Ryo Matsumura (Fujitsu)" <matsumura(dot)ryo(at)fujitsu(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: DDL result is lost by CREATE DATABASE with WAL_LOG strategy
Date: 2023-02-16 06:41:20
Message-ID: 20230216064120.GA2016097@nathanxps13
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On Thu, Feb 16, 2023 at 02:26:55PM +0900, Michael Paquier wrote:
> So, if I am understanding this stuff right, this issue can create data
> corruption once a DDL updates any pages of pg_class stored in a
> template database that gets copied by this routine. In this case, the
> patch sent makes sure that any page copied will get written once a
> checkpoint kicks in. Shouldn't we have at least a regression test for
> such a scenario? The issue can happen when updating a template
> database after creating a database from it, which is less worrying
> than the initial impression I got, still I'd like to think that we
> should have some coverage as of the special logic this code path
> relies on for pg_class when reading its buffers.

I was able to quickly hack together a TAP test that seems to reliably fail
before the fix and pass afterwards. There's probably a better place for
it, though...

--
Nathan Bossart
Amazon Web Services: https://aws.amazon.com

Attachment Content-Type Size
create_db_fix_v2.patch text/x-diff 1.8 KB

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