I'm running a PostgreSQL 11.22 database, and I want to create a new collation to support the Czech language, since I don't see it on the collations list when I select from pg_catalog.
Attempt 1 The documentation claims it is possible to create a collation basing it off of libc like so:
CREATE COLLATION czech (provider = libc, locale = 'cs_CZ');
But I got:
ERROR: could not create locale "cs_CZ": No such file or directory
DETAIL: The operating system could not find any locale data for the locale name "cs_CZ".
Attempt 2 After that, I tried creating a custom collation, in which I could manually set the Czech language's collation rules, like so:
CREATE COLLATION IF NOT EXISTS czech (provider = icu, locale = 'und', rules = '...');
But I got the error
ERROR: collation attribute "rules" not recognized LINE 2: ...OT EXISTS custom (provider = icu, locale = 'und', rules = '...
Do I have an incorrect version of PostgreSQL? Is that a newer feature, or does something else need to be configured?
For the first question, you first have to make sure that the C library has a collation with that name for your current encoding. After you create or install new C library collations, you have to import them into PostgreSQL with
SELECT pg_import_system_collations('pg_catalog');
For the second question, the RULES clause does not exist in the unsupported version 11 of PostgreSQL.