Re: [PATCH] Optimize json_lex_string by batching character copying

On Sun, Aug 21, 2022 at 12:47 PM Nathan Bossart
<nathandbossart@gmail.com> wrote:
>
> 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.

Not at all! However, the 32-bit-element changes are irrelevant for
json, and make review more difficult. I would suggest keeping those in
the other thread starting with whatever refactoring is needed. I can
always rebase over that.

Not a full review, but on a brief look:

- I like the idea of simplifying the assertions, but I can't get
behind using platform lfind to do it, since it has a different API,
requires new functions we don't need, and possibly has portability
issues. A simple for-loop is better for assertions.
- A runtime elog is not appropriate for a compile time check -- use
#error instead.

--
John Naylor
EDB: http://www.enterprisedb.com