Re: [PATCH] Add pg_lfind8_nonzero()

Hi,

On 2025-12-14 21:33:00 +0800, cca5507 wrote:
> Hi hackers,
> 
> I'd like to add pg_lfind8_nonzero() to optimize some code like this:
> 
> ```
>     for (i = 0; i < numberOfAttributes; i++)
>     {
>         if (isnull[i])
>         {
>             hasnull = true;
>             break;
>         }
>     }
> ```

Is code like this ever actually relevant for performance? In cases where the
compiler can't also optimize the code? Unless it is a legitimate bottleneck,
adding more complicated code to optimize the case doesn't make sense.


> create extension test_patch;
> # 4 is the natts
> select test_head(4);
> select test_patch(4);
> 
> Test result:
> natts: 4   head: 1984ns  patch: 2094ns
> natts: 8   head: 3196ns  patch: 641ns
> natts: 16  head: 4589ns  patch: 752ns
> natts: 32  head: 8036ns  patch: 1152ns
> natts: 64  head: 19367ns patch: 2455ns
> natts: 128 head: 33445ns patch: 4018ns
> 
> Looking forward to your comments!
> 

The benchmark really should show performance benefits in at least somewhat
realistic cases (i.e. real users of the functions, even if the workload is a
bit more extreme than it'd be most of the time).

Greetings,

Andres