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

On Tue, 13 Jul 2021 at 15:15, David Rowley <dgrowleyml@gmail.com> wrote:
> In theory, we likely could get rid of the small regression by having
> two versions of ExecSort() and setting the correct one during
> ExecInitSort() by setting the function pointer to the version we want
> to use in sortstate->ss.ps.ExecProcNode.

Just to see how it would perform, I tried what I mentioned above. I've
included what I ended up with in the attached POC patch.

I got the following results on my AMD hardware.

Test master v8 patch comparison
Test1   448.0   671.7   149.9%
Test2   316.4   317.5   100.3%
Test3   299.5   381.6   127.4%
Test4   219.7   229.5   104.5%
Test5   226.3   254.6   112.5%
Test6   197.9   217.9   110.1%
Test7   179.2   185.3   103.4%
Test8   389.2   544.8   140.0%

This time I saw no regression on tests 2, 4 and 7.

I looked to see if there was anywhere else in the executor that
conditionally uses a different exec function in this way and found
nothing, so I'm not too sure if it's a good idea to start doing this.

It would be good to get a 2nd opinion about this idea.  Also, more
benchmark results with v6 and v8 would be good too.

David