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help / color / mirror / Atom feedFrom: Nathan Bossart <[email protected]>
To: KAZAR Ayoub <[email protected]>
Cc: Andres Freund <[email protected]>
Cc: Pg Hackers <[email protected]>
Cc: Neil Conway <[email protected]>
Cc: Manni Wood <[email protected]>
Cc: Andrew Dunstan <[email protected]>
Cc: Shinya Kato <[email protected]>
Cc: Mark Wong <[email protected]>
Cc: Nazir Bilal Yavuz <[email protected]>
Subject: Re: Speed up COPY TO text/CSV parsing using SIMD
Date: Tue, 31 Mar 2026 11:30:54 -0500
Message-ID: <acv2vu8miagnHG1B@nathan> (raw)
In-Reply-To: <CA+K2Runq+1gy8p6a-DsxpT2OkEkEu3cUGsZ9tdiGNrg_=P39gg@mail.gmail.com>
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On Fri, Mar 27, 2026 at 07:48:38PM +0100, KAZAR Ayoub wrote:
> I added a prescan loop inside the simd helpers trying to catch special
> chars in sizeof(Vector8) characters, i measured how good is this at
> reducing the overhead of starting simd and exiting at first vector:
> the scalar loop is better than SIMD for one vector if it finds a special
> character before 6th character, worst case is not a clean vector, where the
> scalar loop needs 20 more cycles compared to SIMD.
> This helps mitigate the case of JSON(B) in CSV format, this is why I only
> added this for CSV case only.
Interesting.
> In a benchmark with 10M early SIMD exit like the JSONB case, the previous
> 3% regression is gone.
While these are nice results, I think it's best that we target v20 for this
patch so that we have more time to benchmark and explore edge cases.
--
nathan
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Subject: Re: Speed up COPY TO text/CSV parsing using SIMD
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