Date: Mon, 2 Mar 2026 13:55:05 -0600
From: Nathan Bossart <nathandbossart@gmail.com>
To: Nazir Bilal Yavuz <byavuz81@gmail.com>
Cc: Manni Wood <manni.wood@enterprisedb.com>, KAZAR Ayoub <ma_kazar@esi.dz>,
	Neil Conway <neil.conway@gmail.com>,
	Andrew Dunstan <andrew@dunslane.net>,
	Shinya Kato <shinya11.kato@gmail.com>,
	PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: Speed up COPY FROM text/CSV parsing using SIMD
Message-ID: <aaXrGSyq4u2d9qEC@nathan>
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On Wed, Feb 25, 2026 at 05:24:27PM +0300, Nazir Bilal Yavuz wrote:
> If anyone has any suggestions/ideas, please let me know!

A couple of random ideas:

* Additional inlining for callers.  I looked around a little bit and didn't
see any great candidates, so I don't have much faith in this, but maybe
you'll see something I don't.

* Disable SIMD if we are consistently getting small rows.  That won't help
your "wide & CSV 1/3" case in all likelihood, but perhaps it'll help with
the regression for narrow rows described elsewhere.

* Surround the variable initializations with "if (simd_enabled)".
Presumably compilers are smart enough to remove those in the non-SIMD paths
already, but it could be worth a try.

* Add simd_enabled function parameter to CopyReadLine(),
NextCopyFromRawFieldsInternal(), and CopyFromTextLikeOneRow(), and do the
bool literal trick in CopyFrom{Text,CSV}OneRow().  That could encourage the
compiler to do some additional optimizations to reduce branching.

-- 
nathan