Re: Eval expression R/O once time (src/backend/executor/execExpr.c)

Em ter., 21 de set. de 2021 às 20:00, Andres Freund <andres@anarazel.de>
escreveu:

> Hi,
>
> On 2021-09-21 18:21:24 -0400, Tom Lane wrote:
> > Andres Freund <andres@anarazel.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!
>
No problem, thanks for taking a look.

regards,
Ranier Vilela