Horton

Re: [PATCH] Optimize json_lex_string by batching character copying

John Naylor <john.naylor@enterprisedb.com>

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From: John Naylor <john.naylor@enterprisedb.com>
To: Andres Freund <andres@anarazel.de>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, Jelte Fennema <Jelte.Fennema@microsoft.com>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>, Merlin Moncure <mmoncure@gmail.com>, Andrew Dunstan <andrew.dunstan@2ndquadrant.com>, Stephen Frost <sfrost@snowman.net>
Date: 2022-07-12T06:57:48Z
Lists: pgsql-hackers 
On Mon, Jul 11, 2022 at 11:07 PM Andres Freund <andres@anarazel.de> wrote:

> I wonder if we can add a somewhat more general function for scanning until
> some characters are found using SIMD? There's plenty other places that
could
> be useful.

In simple cases, we could possibly abstract the entire loop. With this
particular case, I imagine the most approachable way to write the loop
would be a bit more low-level:

while (p < end - VECTOR_WIDTH &&
       !vector_has_byte(p, '\\') &&
       !vector_has_byte(p, '"') &&
       vector_min_byte(p, 0x20))
    p += VECTOR_WIDTH

I wonder if we'd lose a bit of efficiency here by not accumulating set bits
from the three conditions, but it's worth trying.
-- 
John Naylor
EDB: http://www.enterprisedb.com

Commits

  1. Speed up lexing of long JSON strings

  2. Add optimized functions for linear search within byte arrays

  3. Build de-escaped JSON strings in larger chunks during lexing

  4. Simplify json lexing state