Wrong detection of Duplicated indexes

[SButterfly]

create table t
(
    id   bigserial primary key,
    text text not null
);
create index ix_text on t (text);
create index ix_text_collate on t (text COLLATE "C.UTF-8");

[mfvanek]

@SButterfly
I don't think that it's a bug. It's a strange to use collation while creating index. It looks like in this case using of text_pattern_ops would be more preferable.
Could you please provide more information about your use case?

[mfvanek]

Linked issue #61
https://postgrespro.ru/docs/postgresql/10/indexes-opclass

[SButterfly]

Could you please provide more information about your use case?

We use index_with_collate for such queries:
select * from table whete (text collate "C.UTF-8") = ?;
Also we use ilike search
select * from table whete (text collate "C.UTF-8") ilike '%pattern%';

[mfvanek]

how to repro
CREATE COLLATION "C.UTF-8" FROM "en-US-x-icu";
https://dba.stackexchange.com/questions/240930/postgresql-difference-between-collations-c-and-c-utf-8
https://simply.name/ru/pg-lc-collate.html