Re: [PATCH] Use optimized single-datum tuplesort in ExecSort
| От | Ranier Vilela |
|---|---|
| Тема | Re: [PATCH] Use optimized single-datum tuplesort in ExecSort |
| Дата | |
| Msg-id | CAEudQApH-7+MY-PNErMMvkMpyZsYVQTM5ntdD2-Tvy2H2snw6A@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: [PATCH] Use optimized single-datum tuplesort in ExecSort (David Rowley <dgrowleyml@gmail.com>) |
| Список | pgsql-hackers |
Em qua., 14 de jul. de 2021 às 22:22, David Rowley <dgrowleyml@gmail.com> escreveu:
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?
There's a real difference between v8 and v6, if I understood correctly.
v6 the branches is per tuple:
+ if (tupDesc->natts == 1)
v8 the branches is per state:
+ if (ExecGetResultType(outerPlanState(sortstate))->natts == 1)I think that a big different way to solve the problem.
Or am I getting it wrong?
If the sortstate number of attributes is equal to 1, is it worth the same for each tuple?
Can you explain this, please?
regards,
Ranier Vilela
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