Date: Wed, 11 Feb 2026 16:39:43 -0600
From: Nathan Bossart <nathandbossart@gmail.com>
To: Nazir Bilal Yavuz <byavuz81@gmail.com>
Cc: KAZAR Ayoub <ma_kazar@esi.dz>, Neil Conway <neil.conway@gmail.com>,
	Manni Wood <manni.wood@enterprisedb.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
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On Wed, Feb 11, 2026 at 04:27:50PM +0300, Nazir Bilal Yavuz wrote:
> I am sharing a v6 which implements (1). My benchmark results show
> almost no difference for the special-character cases and a nice
> improvement for the no-special-character cases.

Thanks!

> +	/* Initialize SIMD variables */
> +	cstate->simd_enabled = false;
> +	cstate->simd_initialized = false;

> +	/* Initialize SIMD on the first read */
> +	if (unlikely(!cstate->simd_initialized))
> +	{
> +		cstate->simd_initialized = true;
> +		cstate->simd_enabled = true;
> +	}

Why do we do this initialization in CopyReadLine() as opposed to setting
simd_enabled to true when initializing cstate in BeginCopyFrom()?  If we
can initialize it in BeginCopyFrom, we could probably remove
simd_initialized.

> +	if (cstate->simd_enabled)
> +		result = CopyReadLineText(cstate, is_csv, true);
> +	else
> +		result = CopyReadLineText(cstate, is_csv, false);

I know we discussed this upthread, but I'd like to take a closer look at
this to see whether/why it makes such a big difference.  It's a bit awkward
that CopyReadLineText() needs to manage both its local simd_enabled and
cstate->simd_enabled.

+			/* Load a chunk of data into a vector register */
+			vector8_load(&chunk, (const uint8 *) &copy_input_buf[input_buf_ptr]);

As mentioned upthread [0], I think it's worth testing whether processing
multiple vectors worth of data in each loop iteration is worthwhile.

[0] https://postgr.es/m/aSTVOe6BIe5f1l3i%40nathan

-- 
nathan