Re: [PATCH] Optimize json_lex_string by batching character copying

On Fri, Aug 19, 2022 at 01:42:15PM -0700, Nathan Bossart wrote:
> On Fri, Aug 19, 2022 at 03:11:36PM +0700, John Naylor wrote:
>> This is done. Also:
>> - a complete overhaul of the pg_lfind8* tests
>> - using a typedef for the vector type
>> - some refactoring, name changes and other cleanups (a few of these
>> could also be applied to the 32-byte element path, but that is left
>> for future work)
>> 
>> TODO: json-specific tests of the new path
> 
> This looks pretty good to me.  Should we rename vector_broadcast() and
> vector_has_zero() to indicate that they are working with bytes (e.g.,
> vector_broadcast_byte())?  We might be able to use vector_broadcast_int()
> in the 32-bit functions, and your other vector functions already have a
> _byte suffix.
> 
> In general, the approach you've taken seems like a decent readability
> improvement.  I'd be happy to try my hand at adjusting the 32-bit path and
> adding ARM versions of all this stuff.

I spent some more time looking at this one, and I had a few ideas that I
thought I'd share.  0001 is your v6 patch with a few additional changes,
including simplying the assertions for readability, splitting out the
Vector type into Vector8 and Vector32 (needed for ARM), and adjusting
pg_lfind32() to use the new tools in simd.h.  0002 adds ARM versions of
everything, which obsoletes the other thread I started [0].  This is still
a little rough around the edges (e.g., this should probably be more than 2
patches), but I think it helps demonstrate a more comprehensive design than
what I've proposed in the pg_lfind32-for-ARM thread [0].

Apologies if I'm stepping on your toes a bit here.

[0] https://postgr.es/m/20220819200829.GA395728%40nathanxps13

-- 
Nathan Bossart
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