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Re: ICU for global collation

Julien Rouhaud <rjuju123@gmail.com>

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From: Julien Rouhaud <rjuju123@gmail.com>
To: Peter Eisentraut <peter.eisentraut@enterprisedb.com>
Cc: pgsql-hackers <pgsql-hackers@postgresql.org>, Daniel Verite <daniel@manitou-mail.org>
Date: 2022-01-10T06:00:27Z
Lists: pgsql-hackers 
On Mon, Jan 10, 2022 at 11:25:08AM +0800, Julien Rouhaud wrote:
> On Fri, Jan 07, 2022 at 03:25:28PM +0100, Peter Eisentraut wrote:
> > 
> > I tested this a bit.  I used the following setup:
> > 
> > create table t1 (a text);
> > insert into t1 select md5(generate_series(1, 10000000)::text);
> > select count(*) from t1 where a > '';
> > 
> > And then I changed in varstr_cmp():
> > 
> >         if (collid != DEFAULT_COLLATION_OID)
> >             mylocale = pg_newlocale_from_collation(collid);
> > 
> > to just
> > 
> >         mylocale = pg_newlocale_from_collation(collid);
> > 
> > I find that the \timing results are indistinguishable.  (I used locale
> > "en_US.UTF-8" and made sure that that code path is actually hit.)
> > 
> > Does anyone have other insights?
> 
> Looking at the git history, you added this comment in 414c5a2ea65.
> 
> After a bit a digging in the lists, I found that you introduced it to fix a
> reported 13% slowdown in varstr_cmp():
> https://www.postgresql.org/message-id/20110129075253.GA18784%40tornado.leadboat.com
> https://www.postgresql.org/message-id/1296748408.6442.1.camel%40vanquo.pezone.net

So I tried to run Noah's benchmark to see if I could reproduce the slowdown.
Unfortunately the results I'm getting don't really make sense as removing the
optimisation brings a 15% speedup, and with a few more runs I can see that I
have about 25% noise, so there isn't much I can do to help.

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Add CHECK_FOR_INTERRUPTS while restoring changes during decoding.

  2. Improve ICU option handling in CREATE DATABASE

  3. Don't allow creation of database with ICU locale with unsupported encoding

  4. Make locale option behavior more consistent

  5. pg_dump: Dump colliculocale

  6. Remove further unwanted linker flags from perl_embed_ldflags

  7. Doc: document possible need to raise kernel's somaxconn limit.

  8. Reduce warnings with -Wshadow=compatible-local builds

  9. Remove redundant spaces in _outA_Expr() output

  10. Fix outdated --help message for postgres -f

  11. pg_upgrade: Fix version comparison for global ICU support

  12. Silence -Wmaybe-uninitialized compiler warning in dbcommands.c.

  13. Add option to use ICU as global locale provider

  14. DefineCollation() code cleanup

  15. Change collate and ctype fields to type text

  16. Call pg_newlocale_from_collation() also with default collation

  17. Use libc version as a collation version on glibc systems.

  18. Silence -Wmaybe-uninitialized compiler warnings in dbcommands.c.

  19. Make LC_COLLATE and LC_CTYPE database-level settings. Collation and