Re: Optimize WindowAgg's use of tuplestores

Ashutosh Bapat <ashutosh(dot)bapat(dot)oss(at)gmail(dot)com> writes:

> On Fri, Jul 12, 2024 at 11:59 AM Ashutosh Bapat
> <ashutosh(dot)bapat(dot)oss(at)gmail(dot)com> wrote:
>>
>>
> Out of curiosity, I measured the performance with just the "unlikely"
> change and with the full patch. Below are the results
> Testing with 1000000 partitions
...
> latency average = 333.538 ms
>
> with just unlikely change
> Testing with 1000000 partitions
..
> Testing with 1 partitions
>
> There's noticeable change across all the number of partitions with
> just "unlikely" change.

I'm curious about why a 'unlikey' change can cause noticeable change,
especially there is just one function call in the 'if-statement' (I am
thinking more instrucments in the if-statement body, more changes it can
cause).

+ if (unlikely(winstate->buffer == NULL))
+ prepare_tuplestore(winstate);

--
Best Regards
Andy Fan