| From: | James Coleman <jtc331(at)gmail(dot)com> |
|---|---|
| To: | David Rowley <dgrowleyml(at)gmail(dot)com> |
| Cc: | Ranier Vilela <ranier(dot)vf(at)gmail(dot)com>, Ronan Dunklau <ronan(dot)dunklau(at)aiven(dot)io>, PostgreSQL Developers <pgsql-hackers(at)lists(dot)postgresql(dot)org>, Dilip Kumar <dilipbalaut(at)gmail(dot)com> |
| Subject: | Re: [PATCH] Use optimized single-datum tuplesort in ExecSort |
| Date: | 2021-07-15 13:44:14 |
| Message-ID: | CAAaqYe8=rw2_RYr6xrFq6u-f-S4OryCg1OPJfxi-_JPeSmtQVg@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Wed, Jul 14, 2021 at 9:22 PM David Rowley <dgrowleyml(at)gmail(dot)com> wrote:
>
> On Thu, 15 Jul 2021 at 12:30, Ranier Vilela <ranier(dot)vf(at)gmail(dot)com> wrote:
> >
> > Em qua., 14 de jul. de 2021 às 21:21, David Rowley <dgrowleyml(at)gmail(dot)com> escreveu:
> >> But, in v8 there is no additional branch, so no branch to mispredict.
> >> I don't really see how your explanation fits.
> >
> > In v8 the branch occurs at :
> > + if (ExecGetResultType(outerPlanState(sortstate))->natts == 1)
>
> You do know that branch is in a function that's only executed once
> during executor initialization, right?
This is why I have a hard time believing there's a "real" change here
and not the result of either noise or something not really
controllable like executable layout changing.
James
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