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Date: Fri, 16 Sep 2022 09:49:28 +0300
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
Subject: Re: ICU for global collation
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On 2022-09-15 09:52, Kyotaro Horiguchi wrote:
> If I executed initdb as follows, I would be told to specify
> --icu-locale option.
> 
>> $ initdb --encoding sql-ascii --locale-provider icu hoge
>> ...
>> initdb: error: ICU locale must be specified
> 
> However, when I reran the command, it complains about incompatible
> encoding this time.  I think it's more user-friendly to check for the
> encoding compatibility before the check for missing --icu-locale
> option.
> 
> regards.

In continuation of options check: AFAICS the following checks in initdb

	if (locale_provider == COLLPROVIDER_ICU)
	{
		if (!icu_locale)
			pg_fatal("ICU locale must be specified");

		/*
		 * In supported builds, the ICU locale ID will be checked by the
		 * backend during post-bootstrap initialization.
		 */
#ifndef USE_ICU
		pg_fatal("ICU is not supported in this build");
#endif
	}

are executed approximately when they are executed in create database 
after getting all the necessary data from the template database:

if (dblocprovider == COLLPROVIDER_ICU)
{
	/*
	 * This would happen if template0 uses the libc provider but the new
	 * database uses icu.
	 */
	if (!dbiculocale)
		ereport(ERROR,
				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
				 errmsg("ICU locale must be specified")));
}

if (dblocprovider == COLLPROVIDER_ICU)
	check_icu_locale(dbiculocale);

But perhaps the check that --icu-locale cannot be specified unless 
locale provider icu is chosen should also be moved here? So all these 
checks will be in one place and it will use the provider from the 
template database (which could be icu):

$ initdb --locale-provider icu --icu-locale en-US -D data &&
pg_ctl -D data -l logfile start &&
createdb --icu-locale ru-RU --template template0 mydb
...
createdb: error: database creation failed: ERROR:  ICU locale cannot be 
specified unless locale provider is ICU

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