Re: Performance degradation on concurrent COPY into a single relation in PG16.

On Wed, 19 Jul 2023 at 09:24, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
>
> > > 2) pg_strtoint32_safe() got substantially slower, mainly due
> > > to
> > > faff8f8e47f Allow underscores in integer and numeric constants.
> > > 6fcda9aba83 Non-decimal integer literals
> >
> > Agreed.
> >
> I have made some progress on dealing with performance regression on
> single client COPY. I've attached a patch to fix 2). With the patch I
> shared[1] to deal with 1), single client COPY performance seems to be
> now as good as (or slightly better than) PG15 . Here are the results
> (averages of 5 times) of loading 50M rows via COPY:
>

Hmm, I'm somewhat sceptical about this second patch. It's not obvious
why adding such tests would speed it up, and indeed, testing on my
machine with 50M rows, I see a noticeable speed-up from patch 1, and a
slow-down from patch 2:

PG15
====

7390.461 ms
7497.655 ms
7485.850 ms
7406.336 ms

HEAD
====

8388.707 ms
8283.484 ms
8391.638 ms
8363.306 ms

HEAD + P1
=========

7255.128 ms
7185.319 ms
7197.822 ms
7191.176 ms

HEAD + P2
=========

8687.164 ms
8654.907 ms
8641.493 ms
8668.865 ms

HEAD + P1 + P2
==============

7780.126 ms
7786.427 ms
7775.047 ms
7785.938 ms

So for me at least, just applying patch 1 gives the best results, and
makes it slightly faster than PG15 (possibly due to 6b423ec677).

Regards,
Dean