Re: ICU for global collation

Thanks to Kyotaro Horiguchi review we found out that there're
interesting cases due to the order of some ICU checks:

1. ICU locale vs supported encoding:

1.1.

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.

1.2. (ok?)

$ initdb --encoding sql-ascii --icu-locale en-US hoge
initdb: error: --icu-locale cannot be specified unless locale provider
"icu" is chosen

$ initdb --encoding sql-ascii --icu-locale en-US --locale-provider icu
hoge
...
initdb: error: encoding mismatch
initdb: detail: The encoding you selected (SQL_ASCII) is not supported
with the ICU provider.
initdb: hint: Rerun initdb and either do not specify an encoding
explicitly, or choose a matching combination.

$ createdb --encoding sql-ascii --icu-locale en-US hoge
createdb: error: database creation failed: ERROR: ICU locale cannot be
specified unless locale provider is ICU
$ createdb --encoding sql-ascii --icu-locale en-US --locale-provider icu
hoge
createdb: error: database creation failed: ERROR: encoding "SQL_ASCII"
is not supported with ICU provider

2. For builds without ICU:

2.1.

$ initdb --locale-provider icu hoge
...
initdb: error: ICU locale must be specified

$ initdb --locale-provider icu --icu-locale en-US hoge
...
initdb: error: ICU is not supported in this build

$ createdb --locale-provider icu hoge
createdb: error: database creation failed: ERROR: ICU locale must be
specified

$ createdb --locale-provider icu --icu-locale en-US hoge
createdb: error: database creation failed: ERROR: ICU is not supported
in this build

IMO, it would be more user-friendly to inform an unsupported build in
the first runs too..

2.2. (ok?)

$ initdb --icu-locale en-US hoge
initdb: error: --icu-locale cannot be specified unless locale provider
"icu" is chosen
$ initdb --icu-locale en-US --locale-provider icu hoge
...
initdb: error: ICU is not supported in this build

$ createdb --icu-locale en-US hoge
createdb: error: database creation failed: ERROR: ICU locale cannot be
specified unless locale provider is ICU
$ createdb --icu-locale en-US --locale-provider icu hoge
createdb: error: database creation failed: ERROR: ICU is not supported
in this build

2.3.

$ createdb --locale-provider icu --icu-locale en-US --encoding sql-ascii
hoge
createdb: error: database creation failed: ERROR: encoding "SQL_ASCII"
is not supported with ICU provider
$ createdb --locale-provider icu --icu-locale en-US --encoding utf8 hoge
createdb: error: database creation failed: ERROR: ICU is not supported
in this build

IMO, it would be more user-friendly to inform an unsupported build in
the first run too..

3.

The locale provider is ICU, but it has not yet been set from the
template database:

> $ 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