From: Nathan Bossart <nathandbossart@gmail.com>
To: Michael Paquier <michael@paquier.xyz>
Cc: Gurjeet Singh <gurjeet@singh.im>
Cc: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Richard Veselý <richard.vesely@softea.sk>
Cc: pgsql-bugs@lists.postgresql.org
Subject: Re: Fwd: BUG #18016: REINDEX TABLE failure
Date: Fri, 1 Sep 2023 09:55:35 -0700
Message-ID: <20230901165535.GB3178187@nathanxps13> (raw)
In-Reply-To: <20230728180056.GB3661419@nathanxps13>
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<CABwTF4U+t-8sD2y2xhgHyj=ovPMbrsNJO5F49nvZZtpwFkwWDA@mail.gmail.com>
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<20230727231441.GB3612597@nathanxps13>
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<20230728180056.GB3661419@nathanxps13>
On Fri, Jul 28, 2023 at 11:00:56AM -0700, Nathan Bossart wrote:
> On Fri, Jul 28, 2023 at 10:50:50AM +0900, Michael Paquier wrote:
>> On Thu, Jul 27, 2023 at 04:14:41PM -0700, Nathan Bossart wrote:
>>> On Wed, Jul 26, 2023 at 06:43:18PM -0700, Gurjeet Singh wrote:
>>>> I felt the need for that paragraph, because it doesn't feel obvious to
>>>> me as to why we can't simply reindex the toast table as the first
>>>> thing in this function; the toast table reindex will trigger CCI, and
>>>> that'd be bad if done before RelationGetIndexList().
>>>
>>> I see. I'd suggest referencing the comment above the function, but in
>>> general I do think having a comment about this is appropriate.
>>
>> + * This should be done after the suppression of the use of indexes (above),
>> + * because the recursive call to reindex_relation() below will invoke
>> + * CommandCounterIncrement(), which may prevent enumeration of the indexes
>> + * on the table.
>>
>> This does not explain the reason why this would prevent the creation
>> of a consistent index list fetched from the parent table, does it?
>> Would some indexes be missing from what should be reindexed? Or some
>> added unnecessarily? Would that be that an incorrect list?
>
> IIUC the issue is that something (e.g., VACUUM FULL, CLUSTER) might've just
> rebuilt the heap, so if we CCI'd before gathering the list of indexes, the
> new heap contents would become visible, and the indexes would be
> inconsistent with the heap. This is a problem when the relation in
> question is a system catalog that needs to be consulted to gather the list
> of indexes. To handle this, we avoid the CCI until after gathering the
> indexes so that the old heap contents appear valid and can be used as
> needed. Once that is done, we mark the indexes as pending-rebuild and do a
> CCI, at which point the indexes become inconsistent with the heap. This
> behavior appears to have been added by commit b9b8831.
How do we move this one forward? Michael and I provided some feedback
about the comment, but AFAICT this patch is in good shape otherwise.
Gurjeet, would you mind putting together a new version of the patch so that
we can close on this one?
--
Nathan Bossart
Amazon Web Services: https://aws.amazon.com
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To: pgsql-bugs@postgresql.org
Cc: nathandbossart@gmail.com, michael@paquier.xyz, gurjeet@singh.im, tgl@sss.pgh.pa.us, richard.vesely@softea.sk, pgsql-bugs@lists.postgresql.org
Subject: Re: Fwd: BUG #18016: REINDEX TABLE failure
In-Reply-To: <20230901165535.GB3178187@nathanxps13>
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