Date: Tue, 10 Mar 2026 14:16:57 -0500
From: Nathan Bossart <nathandbossart@gmail.com>
To: KAZAR Ayoub <ma_kazar@esi.dz>
Cc: Andres Freund <andres@anarazel.de>,
	Pg Hackers <pgsql-hackers@postgresql.org>,
	Neil Conway <neil.conway@gmail.com>,
	Manni Wood <manni.wood@enterprisedb.com>,
	Andrew Dunstan <andrew@dunslane.net>,
	Shinya Kato <shinya11.kato@gmail.com>,
	Mark Wong <markwkm@gmail.com>,
	Nazir Bilal Yavuz <byavuz81@gmail.com>
Subject: Re: Speed up COPY TO text/CSV parsing using SIMD
Message-ID: <abBuKalOno33MQFw@nathan>
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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@anarazel.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