From: Michael Paquier <michael@paquier.xyz>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Cc: exclusion@gmail.com
Cc: pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #18014: Releasing catcache entries makes schema_to_xmlschema() fail when parallel workers are used
Date: Wed, 26 Jul 2023 12:32:38 +0900
Message-ID: <ZMCT1rszfKIiNLpk@paquier.xyz> (raw)
In-Reply-To: <1821881.1690339317@sss.pgh.pa.us>
References: <00e24aa6-5d03-99b6-ab41-495a35fc93f6@gmail.com>
<982076.1689967306@sss.pgh.pa.us>
<5bd4cbfe-fc71-c576-851d-3bb21ef5c080@gmail.com>
<20230726.112923.27361680552823861.horikyota.ntt@gmail.com>
<1821881.1690339317@sss.pgh.pa.us>
On Tue, Jul 25, 2023 at 10:41:57PM -0400, Tom Lane wrote:
> As I said earlier, I think that's a purely coincidental "fix" for
> this specific manifestation. Either SearchSysCacheExists followed
> by a syscache lookup of the same tuple should be considered safe,
> or it shouldn't. If it should be considered safe, we need to fix the
> cache-clobber test scaffolding to not give a false positive. While if
> it shouldn't, we need to get rid of that coding pattern, not apply
> high-level band-aids that remove just one particular path to reaching
> the problem. I'm not dead set on either answer at this point, but
> I think those are the plausible alternatives.
FWIW, I'm having a hard time thinking about a reason that we should
not support SearchSysCacheExists()+lookup to be a valid pattern, even
if the cache is clobbered. I am pretty sure that there are other code
paths in the tree, not mentioned on this thread, that do exactly that
(haven't checked, but indexcmds.c is one coming in mind).
--
Michael
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To: pgsql-bugs@postgresql.org
Cc: michael@paquier.xyz, tgl@sss.pgh.pa.us, horikyota.ntt@gmail.com, exclusion@gmail.com, pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #18014: Releasing catcache entries makes schema_to_xmlschema() fail when parallel workers are used
In-Reply-To: <ZMCT1rszfKIiNLpk@paquier.xyz>
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