From: Vik Fearing <vik@postgresfriends.org>
To: Christophe Pettus <xof@thebuild.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: jinhui.lai@qq.com
Cc: pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #19059: PostgreSQL fails to evaluate the cheaper expression first, leading to 45X performance degradation
Date: Sun, 21 Sep 2025 11:09:02 +0200
Message-ID: <f5ab4542-acfa-4939-a6aa-0e42b69bb46a@postgresfriends.org> (raw)
In-Reply-To: <84B5D601-C007-4B07-9ECB-CDD06E47B949@thebuild.com>
References: <19059-c751eed385314309@postgresql.org>
<2510592.1758403162@sss.pgh.pa.us>
<84B5D601-C007-4B07-9ECB-CDD06E47B949@thebuild.com>
On 21/09/2025 00:54, Christophe Pettus wrote:
>> On Sep 20, 2025, at 14:19, Tom Lane<tgl@sss.pgh.pa.us> wrote:
>> While we've not gotten a huge amount of push-back about the top-level
>> re-ordering, there's been some complaints. So I'm not eager to
>> propagate the idea further down.
> And tangentially, doesn't the SQL standard make it implementation-defined if OR short-circuits or not?
>
Not that I can see. The only implementation-defined mention in <boolean
value expression> is:
"If the SQL-implementation supports Feature T101, “Enhanced nullability
determination”, and if BVE conforms to an implementation-defined (IE011)
rule that enables the SQL-implementation to correctly infer that, when
BVE is True, then X cannot be null, then BVE is a known-not-null
condition for X. "
--
Vik Fearing
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Cc: vik@postgresfriends.org, xof@thebuild.com, tgl@sss.pgh.pa.us, jinhui.lai@qq.com, pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #19059: PostgreSQL fails to evaluate the cheaper expression first, leading to 45X performance degradation
In-Reply-To: <f5ab4542-acfa-4939-a6aa-0e42b69bb46a@postgresfriends.org>
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