Date: Fri, 28 Apr 2023 15:06:28 +0900 (JST)
Message-Id: <20230428.150628.727832009396744479.horikyota.ntt@gmail.com>
To: michael@paquier.xyz
Cc: exclusion@gmail.com, pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #17804: Assertion failed in pg_stat after fetching from
 pg_stat_database and switching cache->snapshot
From: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
In-Reply-To: <20230428.150404.2168290194163999912.horikyota.ntt@gmail.com>
References: <0d45c9c1-17a1-932f-3925-86484f150c94@gmail.com>
	<ZEtNg1EpciAQ5fjX@paquier.xyz>
	<20230428.150404.2168290194163999912.horikyota.ntt@gmail.com>
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At Fri, 28 Apr 2023 15:04:04 +0900 (JST), Kyotaro Horiguchi <horikyota.ntt@gmail.com> wrote in 
> At Fri, 28 Apr 2023 13:37:23 +0900, Michael Paquier <michael@paquier.xyz> wrote in 
> > FWIW, I was looking at this patch and this proposal of relying on a
> > static flag to conditionally clear a snapshot looks rather brittle by
> > design to me because this relies on quite a few assumptions that the
> > snapshot will always be cleared when necessary, as proved by the two
> > code paths of pgstat.c patched where each gain a check on
> 
> pgstat_get_stat_snapshot_timestmp() necessarily requires that. Just

Sorry, this is actually the opposite.

pgstat_get_stat_snapshot_timestmp() doesn't necessarily requires that. Just

> for seeming consistency.  The only significant part is
> gstat_prep_snapshot, which is always called when the caller wants a
> snapshot.

Regards.

-- 
Kyotaro Horiguchi
NTT Open Source Software Center