From: | Andres Freund <andres(at)anarazel(dot)de> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Ranier Vilela <ranier(dot)vf(at)gmail(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Eval expression R/O once time (src/backend/executor/execExpr.c) |
Date: | 2021-09-21 23:00:55 |
Message-ID: | 20210921230055.sbdfdli6myiimxvm@alap3.anarazel.de |
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Lists: | pgsql-hackers |
Hi,
On 2021-09-21 18:21:24 -0400, Tom Lane wrote:
> Andres Freund <andres(at)anarazel(dot)de> writes:
> > On 2021-09-21 15:09:11 -0300, Ranier Vilela wrote:
> >> Currently when determining where CoerceToDomainValue can be read,
> >> it evaluates every step in a loop.
> >> But, I think that the expression is immutable and should be solved only
> >> once.
>
> > What is immutable here?
>
> I think Ranier has a point here. The clear intent of this bit:
>
> /*
> * If first time through, determine where CoerceToDomainValue
> * nodes should read from.
> */
> if (domainval == NULL)
> {
>
> is that we only need to emit the EEOP_MAKE_READONLY once when there are
> multiple CHECK constraints. But because domainval has the wrong lifespan,
> that test is constant-true, and we'll do it over each time to little
> purpose.
Oh, I clearly re-skimmed the code too quickly. Sorry for that!
> (AFAICS anyway)
>
> I'm unexcited by the proposed move of the save_innermost_domainval/null
> variables, though. It adds no correctness and it forces an additional
> level of indentation of a good deal of code, as the patch fails to show.
Yea.
Greetings,
Andres Freund
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