From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com> |
Cc: | Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>, Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Check-out mutable functions in check constraints |
Date: | 2019-07-12 23:59:13 |
Message-ID: | 14835.1562975953@sss.pgh.pa.us |
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Lists: | pgsql-hackers |
Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com> writes:
> On Fri, Jul 12, 2019 at 02:00:25PM +0200, Pavel Stehule wrote:
>>> Mutable function are allowed in check constraint expressions but
>>> it is not right. The attached is a proposed fix for it including
>>> regression test.
> Yes, and the question is whether this is the right thing to do (I think
> it probably is).
I'm pretty sure this change has been proposed before, and rejected before.
Has anybody excavated in the archives for prior discussions?
> OTOH, even if we prohibit mutable functions in check constraints, people
> can still create triggers doing those checks (and shoot themselves in
> the foot that way).
There are, and always will be, lots of ways to shoot yourself in the foot.
In the case at hand, I fear we might just encourage people to mark
functions as immutable when they really aren't --- which will make their
problems *worse* not better, because now other uses besides check
constraints will also be at risk of misoptimization.
regards, tom lane
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