| From: | Nathan Bossart <nathandbossart(at)gmail(dot)com> |
|---|---|
| To: | KAZAR Ayoub <ma_kazar(at)esi(dot)dz> |
| Cc: | Andres Freund <andres(at)anarazel(dot)de>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org>, Neil Conway <neil(dot)conway(at)gmail(dot)com>, Manni Wood <manni(dot)wood(at)enterprisedb(dot)com>, Andrew Dunstan <andrew(at)dunslane(dot)net>, Shinya Kato <shinya11(dot)kato(at)gmail(dot)com>, Mark Wong <markwkm(at)gmail(dot)com>, Nazir Bilal Yavuz <byavuz81(at)gmail(dot)com> |
| Subject: | Re: Speed up COPY TO text/CSV parsing using SIMD |
| Date: | 2026-03-10 19:16:57 |
| Message-ID: | abBuKalOno33MQFw@nathan |
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| Lists: | pgsql-hackers |
On Sat, Feb 14, 2026 at 04:02:21PM +0100, KAZAR Ayoub wrote:
> On Thu, Feb 12, 2026 at 10:25 PM Andres Freund <andres(at)anarazel(dot)de> wrote:
>> I have a hard time believing that adding a strlen() to the handling of a
>> short column won't be a measurable overhead with lots of short attributes.
>> Particularly because the patch afaict will call it repeatedly if there are
>> any to-be-escaped characters.
>
> [...]
>
> 1000 columns:
> TEXT: 17% regression
> CSV: 3.4% regression
>
> 500 columns:
> TEXT: 17.7% regression
> CSV: 3.1% regression
>
> 100 columns:
> TEXT: 17.3% regression
> CSV: 3% regression
>
> A bit unstable results, but yeah the overhead for worse cases like this is
> really significant, I can't argue whether this is worth it or not, so
> thoughts on this ?
I seriously doubt we'd commit something that produces a 17% regression
here. Perhaps we should skip the SIMD paths whenever transcoding is
required.
--
nathan
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