Hi,
On Fri, 13 Mar 2026 at 14:57, Nazir Bilal Yavuz <byavuz81@gmail.com> wrote:
>
> Unfortunately, v15 causes a regression for a 'csv & wide & 1/3' case
> on my end. v14 was taking 8000ms but v15 took ~9100ms. If we add the
> tmp_hit_eof variable then the regression disappears. Also, if I use a
> struct like below, regression disappears again.
> When I removed the tmp_hit_eof variable on v14, I didn't encounter any
> regression. I really don't understand why this is happening on my end.
> Manni didn't encounter any regression on the benchmark [1].
Problem might be related to gcc. I am using Debian Trixie and my
current gcc version is 'gcc version 14.2.0 (Debian 14.2.0-19)'. If I
compile Postgres with 'Debian clang version 19.1.7 (3+b1)', then there
is no regression, which makes more sense IMO.
Here is a comparison for csv & wide & 1/3 case. Postgres is compiled
with buildtype=debugoptimized and default_toast_compression is lz4.
+--------------------------------+
| CSV & WIDE & 1/3, LZ4, -O2 |
+--------------+--------+--------+
| | gcc | clang |
| | 14.0.2 | 19.1.7 |
+--------------+--------+--------+
| old master | 8250 | 10400 |
+--------------+--------+--------+
| v14 | 8100 | 9800 |
+--------------+--------+--------+
| v15 | 9200 | 9800 |
+--------------+--------+--------+
| v15 + struct | 7750 | 9800 |
+--------------+--------+--------+
--
Regards,
Nazir Bilal Yavuz
Microsoft
