Horton

Re: [PATCH] Use optimized single-datum tuplesort in ExecSort

James Coleman <jtc331@gmail.com>

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From: James Coleman <jtc331@gmail.com>
To: David Rowley <dgrowleyml@gmail.com>
Cc: Ranier Vilela <ranier.vf@gmail.com>, Ronan Dunklau <ronan.dunklau@aiven.io>, PostgreSQL Developers <pgsql-hackers@lists.postgresql.org>, Dilip Kumar <dilipbalaut@gmail.com>
Date: 2021-07-15T13:44:14Z
Lists: pgsql-hackers 
On Wed, Jul 14, 2021 at 9:22 PM David Rowley <dgrowleyml@gmail.com> wrote:
>
> On Thu, 15 Jul 2021 at 12:30, Ranier Vilela <ranier.vf@gmail.com> wrote:
> >
> > Em qua., 14 de jul. de 2021 às 21:21, David Rowley <dgrowleyml@gmail.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

Commits

  1. Make nodeSort.c use Datum sorts for single column sorts