PG Bug reporting form <noreply@postgresql.org> writes:
> Postgres can't upper lower diacritic character of Croatina alfabet
> š,đ,č,ć,ž,Š,Đ,Č,Ć,Ž,
This isn't a Postgres issue; it's going to depend mainly on what
operating system locale settings (lc_collate and/or lc_ctype)
you've chosen for the database.
I'm not sure what the appropriate setting is on Windows, unfortunately.
regards, tom lane