I want to get a query result by locale, but it appears that
LC_COLLATE cannot be changed.
This is an example of changing en_US.UTF-8 (default) to ja_JP.utf8:
Create the collation with
CREATE COLLATION ja_JP (locale = 'ja_JP.utf8');
And then execute the following query:
ALTER TABLE table_name ALTER COLUMN column_name TYPE VARCHAR COLLATE ja_JP;
Please refer to https://www.postgresql.org/docs/current/collation.html for more details.