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