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Re: ICU for global collation

Marina Polyakova <m.polyakova@postgrespro.ru>

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From: Marina Polyakova <m.polyakova@postgrespro.ru>
To: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Cc: pgsql-hackers@postgresql.org, pryzby@telsasoft.com, rjuju123@gmail.com, daniel@manitou-mail.org, AndrewBille@gmail.com, michael@paquier.xyz, peter.eisentraut@enterprisedb.com
Date: 2022-09-16T07:31:42Z
Lists: pgsql-hackers 
On 2022-09-16 07:55, Kyotaro Horiguchi wrote:
> At Thu, 15 Sep 2022 18:41:31 +0300, Marina Polyakova
> <m.polyakova@postgrespro.ru> wrote in
>> P.S. While working on the patch, I discovered that UTF8 encoding is
>> always used for the ICU provider in initdb unless it is explicitly
>> specified by the user:
>> 
>> if (!encoding && locale_provider == COLLPROVIDER_ICU)
>> 	encodingid = PG_UTF8;
>> 
>> IMO this creates additional errors for locales with other encodings:
>> 
>> $ initdb --locale de_DE.iso885915@euro --locale-provider icu
>> --icu-locale de-DE
>> ...
>> initdb: error: encoding mismatch
>> initdb: detail: The encoding you selected (UTF8) and the encoding that
>> the selected locale uses (LATIN9) do not match. This would lead to
>> misbehavior in various character string processing functions.
>> initdb: hint: Rerun initdb and either do not specify an encoding
>> explicitly, or choose a matching combination.
>> 
>> And ICU supports many encodings, see the contents of pg_enc2icu_tbl in
>> encnames.c...
> 
> It seems to me the best default that fits almost all cases using icu
> locales.
> 
> So, we need to specify encoding explicitly in that case.
> 
> $ initdb --encoding iso-8859-15 --locale de_DE.iso885915@euro
> --locale-provider icu --icu-locale de-DE
> 
> However, I think it is hardly understantable from the documentation.
> 
> (I checked this using euc-jp [1] so it might be wrong..)
> 
> [1] initdb --encoding euc-jp --locale ja_JP.eucjp --locale-provider
> icu --icu-locale ja-x-icu
> 
> regards.

Thank you!

IMO it is hardly understantable from the program output either - it 
looks like I manually chose the encoding UTF8. Maybe first inform about 
selected encoding?..

diff --git a/src/bin/initdb/initdb.c b/src/bin/initdb/initdb.c
index 
6aeec8d426c52414b827686781c245291f27ed1f..348bbbeba0f5bc7ff601912bf883510d580b814c 
100644
--- a/src/bin/initdb/initdb.c
+++ b/src/bin/initdb/initdb.c
@@ -2310,7 +2310,11 @@ setup_locale_encoding(void)
  	}

  	if (!encoding && locale_provider == COLLPROVIDER_ICU)
+	{
  		encodingid = PG_UTF8;
+		printf(_("The default database encoding has been set to \"%s\" for a 
better experience with the ICU provider.\n"),
+			   pg_encoding_to_char(encodingid));
+	}
  	else if (!encoding)
  	{
  		int			ctype_enc;

ISTM that such choices (e.g. UTF8 for Windows in some cases) are 
described in the documentation [1] as

By default, initdb uses the locale provider libc, takes the locale 
settings from the environment, and determines the encoding from the 
locale settings. This is almost always sufficient, unless there are 
special requirements.

[1] https://www.postgresql.org/docs/devel/app-initdb.html

-- 
Marina Polyakova
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company

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