Re: [PATCH] Optimize json_lex_string by batching character copying

On Wed, Aug 24, 2022 at 11:56 PM Nathan Bossart
<nathandbossart(at)gmail(dot)com> wrote:
>
> On Wed, Aug 24, 2022 at 11:59:25AM +0700, John Naylor wrote:
> > It seems "scalar" would be a bad choice since it already means
> > (confusingly) operating on the least significant element of a vector.
> > I'm thinking of *_has and *_has_le, matching the already existing in
> > the earlier patch *_has_zero.
>
> That seems reasonable to me.

Okay, done that way, also in v9:
- a convenience macro in the test suite which is handy now and can be
used for 32-bit element tests if we like
- more tests
- pgindent and some additional comment smithing
- split out the json piece for a later commit
- For the following comment, pgindent will put spaced operands on a
separate line which is not great for readability. and our other
reference to the Stanford bithacks page keeps the in-page link, and I
see no reason to exclude it -- if it goes missing, the whole page will
still load. So I put back those two details.

+ * To find bytes <= c, we can use bitwise operations to find
bytes < c+1,
+ * but it only works if c+1 <= 128 and if the highest bit in v
is not set.
+ * Adapted from
+ * https://graphics.stanford.edu/~seander/bithacks.html#HasLessInWord

I think I'll go ahead and commit 0001 in a couple days pending further comments.

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