Re: Collation & ctype method table, and extension hooks

On Fri, 2024-11-01 at 14:08 +0100, Andreas Karlsson wrote:
> I think adding such a small file would make life easier for people
> new
> to the collation part of the code base. It would be a nice symmetry
> between collation providers and where code for them can be found.

Done.

> >
> For me combining them would make the intention of the code easier to
> understand since aren't the casemap functions just a set of
> "ctype_methods"?

Done.

There is a bit of weirdness in libc because:

* Single byte encodings use the single-byte isupper(), toupper(), etc.
* UTF8 encoding uses wide character iswupper(), towupper(), etc.
* Non-UTF8 multibyte encodings use isupper() for pattern matching but
towupper() for case mapping

that weirdness existed before, but it's a bit more obvious what's
happening now.

> > > This commit makes me tempted to handle the ctype_is_c logic for
> > > character classes also in callbacks and remove the if in
> > > functions
> > > like
> > > pg_wc_ispunct(). But this si something that would need to be
> > > benchmarked.

I like this idea, but it can be a follow up.

Attached new patchset.

I also tried some performance tests again. I used smalltext (a table of
10M ~30-character strings) and bigtext (a table of 32768 rows, each
containing the 100KiB source of https://en.wikipedia.org/wiki/Diacritic
). And I then ran the following regex on each:

select count(*) from thetable
where t ~
'[[:digit:]][[:space:]][[:punct:]][[:alpha:]][[:lower:]][[:upper:]]';

for "C", "en_US", and "en-US-x-icu". The timings for smalltext were
indistinguishable between master and the patched version. The timings
for bigtext were pretty noisy so it's hard to tell if there was a
regression or not, but I saw some evidence in the profile that
char_properties has a cost (~1%). I'm not sure if that's a significant
concern or not.

Which API do you think is the right one? Individual functions testing
individual properties, or something like char_properties() that can
test several at once?

Regards,
Jeff Davis