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From: Nathan Bossart <nathandbossart@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Alexander Lakhin <exclusion@gmail.com>
Cc: Sami Imseih <samimseih@gmail.com>
Cc: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
Cc: Robert Treat <rob@xzilla.net>
Cc: satyanarlapuram@gmail.com, pgsql-hackers <pgsql-hackers@postgresql.org>
Cc: tndrwang@gmail.com
Subject: Re: Add pg_stat_autovacuum_priority
Date: Wed, 8 Apr 2026 12:56:09 -0500
Message-ID: <adaWuTR7oCKodH7k@nathan> (raw)
In-Reply-To: <3077290.1775668665@sss.pgh.pa.us>
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On Wed, Apr 08, 2026 at 01:17:45PM -0400, Tom Lane wrote:
> Alexander Lakhin <exclusion@gmail.com> writes:
>> Please look at a new anomaly, I and SQLsmith have discovered:
>> SELECT (SELECT score FROM pg_stat_get_autovacuum_scores() LIMIT 1),
>>      (SELECT score FROM pg_stat_get_autovacuum_scores() LIMIT 1);
>> ERROR:  detected double pfree in PgStat Snapshot 0x5f6fa4d95d50
> 
> Good catch, but you're not the first:
> 
> https://www.postgresql.org/message-id/CAHewXNkJKdwb3D5OnksrdOqzqUnXUEMpDam1TPW0vfUkW%3D7jUw%40mail.g...

Hm.  I can't get excited about checking pgstat_fetch_consistency (as
proposed in that other report), but I see that commit 02502c1bca added the
freeing behavior in question.  I wonder if it makes sense to just skip
freeing when relation_needs_vacanalyze() is called from the view, i.e., not
an autovacuum worker.  On the other hand, maybe we shouldn't be caching
entries for a view like this that looks through all tables in the
database...

-- 
nathan





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  Cc: nathandbossart@gmail.com, tgl@sss.pgh.pa.us, exclusion@gmail.com, samimseih@gmail.com, bharath.rupireddyforpostgres@gmail.com, rob@xzilla.net, tndrwang@gmail.com
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