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From: Nazir Bilal Yavuz <[email protected]>
To: Manni Wood <[email protected]>
Cc: KAZAR Ayoub <[email protected]>
Cc: Nathan Bossart <[email protected]>
Cc: Andrew Dunstan <[email protected]>
Cc: Neil Conway <[email protected]>
Cc: Shinya Kato <[email protected]>
Cc: PostgreSQL-development <[email protected]>
Subject: Re: Speed up COPY FROM text/CSV parsing using SIMD
Date: Mon, 9 Mar 2026 16:43:00 +0300
Message-ID: <CAN55FZ0sgNGT5AmGd1Pv3Wu--uUE1jSugh2REqNa4d55KdPvAw@mail.gmail.com> (raw)
In-Reply-To: <CAKWEB6pWU+2mUa41t0Tb+3XmKyDuGSS=8XaDirumjSc9=d8WJQ@mail.gmail.com>
References: <aZ3kYQnF9_u6sUQp@nathan>
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Hi Manni!

On Mon, 9 Mar 2026 at 16:31, Manni Wood <[email protected]> wrote:
>
> I was being too brief.
>
> The benchmarks I shared were absolutely with lz4 compiled in and 'default_toast_compression = lz4' set in postgresql.conf for every postgres instance I tested with. (Furthermore, I ran `show default_toast_compression` via `psql` on each postgres instance to be sure 'default_toast_compression = lz4' was really set!)
>
> Also, all were compiled using meson using `debugoptimized` which results in `-g -O2`.
>
> So those are the benchmarks that I shared.

Thanks for the clarification.

> OK, so my final question, hopefully clarified: If I run additional benchmarks where pglz is used for default_toast_compression, is it enough to use the instances I have already compiled with lz4 in them, but with 'default_toast_compression = pglz` explicitly set in postgresql.conf in a brand new data dir created by initdb? (In other words, existing data dir deleted, then initdb run to make a new data dir, then postgresql.conf edited to ensure 'default_toast_compression = pglz` explicitly set, then and only then starting up the cluster for the first time... and finally verifying via `show default_toast_compression` for good measure.)
>
> Or should I re-compile with the lz4-is-now-the-default commit completely excised?

Yes, it is clear now; thanks. You don't need to compile without the
lz4-is-now-the-default commit. You can compile with lz4 commit and set
the 'default_toast_compression = pglz' in the postgresql.conf like you
said. This should be enough.

-- 
Regards,
Nazir Bilal Yavuz
Microsoft





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