From: | Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> |
---|---|
To: | Heikki Linnakangas <hlinnaka(at)iki(dot)fi> |
Cc: | pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Commit/abort WAL records with dropped rels missing XLR_SPECIAL_REL_UPDATE |
Date: | 2020-08-15 05:35:43 |
Message-ID: | CAA4eK1Lf-typx7ngR8igFqDRoayLQmUmQh0yMd=RAUrdPSg96Q@mail.gmail.com |
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On Fri, Aug 14, 2020 at 2:17 PM Heikki Linnakangas <hlinnaka(at)iki(dot)fi> wrote:
>
> While hacking on pg_rewind, I noticed that commit and abort WAL records
> are never marked with the XLR_SPECIAL_REL_UPDATE flag. But if the record
> contains "dropped relfilenodes", surely it should be?
>
Right.
> It's harmless as far as the backend and all the programs in PostgreSQL
> repository are concerned, but the point of XLR_SPECIAL_REL_UPDATE is to
> aid external tools that try to track which files are modified. Attached
> is a patch to fix it.
>
> It's always been like that, but I am not going backport, for fear of
> breaking existing applications. If a program reads the WAL, and would
> actually need to do something with commit records dropping relations,
> that seems like such a common scenario that the author should've thought
> about it and handled it even without the flag reminding about it. Fixing
> it in master ought to be enough.
>
+1 for doing it in master only. Even if someone comes up with such a
scenario for back-branches, we can revisit our decision to backport
this but like you, I also don't see any pressing need to do it now.
--
With Regards,
Amit Kapila.
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