Re: Speed up COPY FROM text/CSV parsing using SIMD - Mailing list pgsql-hackers

Hi,

On Tue, 24 Feb 2026 at 07:44, Manni Wood <manni.wood@enterprisedb.com> wrote:
>
> Hello!
>
> I ran some speed tests on Nazir's v10 SIMD-only patch. I'm a bit surprised at the regression for x86 with wide rows for the 1/3rd special characters scenarios. I'm hoping it's something I did wrong. If anyone else has numbers to share, that would be excellent.

Thank you for doing this!

I see similar regression on the wide & CSV 1/3 case by using your
benchmark script. I didn't see this regression when I used my
benchmark while sharing v9 [1].

+-------------+---------------------------+---------------------------+
|             |            Text           |            CSV            |
+-------------+-------------+-------------+-------------+-------------+
|  WIDE TEST  |     None    |     1/3     |     None    |     1/3     |
+-------------+-------------+-------------+-------------+-------------+
|    Master   |     9996    |    10769    |    11548    |    13960    |
+-------------+-------------+-------------+-------------+-------------+
|     v10     | 8912 %-10.8 | 10902 %+1.2 | 8952 %-22.4 | 15123 %+8.3 |
+-------------+-------------+-------------+-------------+-------------+
|             |             |             |             |             |
+-------------+-------------+-------------+-------------+-------------+
|             |            Text           |             |     CSV     |
+-------------+-------------+-------------+-------------+-------------+
| NARROW TEST |     None    |     1/3     |     None    |     1/3     |
+-------------+-------------+-------------+-------------+-------------+
|    Master   |     9441    |     9561    |     9734    |     9830    |
+-------------+-------------+-------------+-------------+-------------+
|     v10     |  9291 %-1.5 |  9504 -%0.5 |  9644 %-0.9 | 10078 %-2.4 |
+-------------+-------------+-------------+-------------+-------------+

I will investigate this. However, please note that the current master
includes the inlining commit (dc592a4155), which makes the COPY FROM
faster. In my case,

1: current master without dc592a4155: 14400ms
2: current master: 13960ms (%3 improvement against #1)
3: current master + SIMD: 15123ms (%5 regression against #1 and %8
regression against #2)

Is it possible for you to do a similar test? I mean dropping
dc592a4155 from the current master and re-running the benchmark, that
would be helpful.

[1] https://postgr.es/m/CAN55FZ0MiFCgK26gRgE05a%3D_ggenkxDM8H%3DA2uTHpywczqt%3D-Q%40mail.gmail.com