PG Bug reporting form <noreply(at)postgresql(dot)org> writes:
> PostgreSQL's unaccent module does not use Unicode normalisation, but only a
> simple search-and-replace dictionary. The dictionary, unaccent.rules
> (https://github.com/postgres/postgres/blob/master/contrib/unaccent/unaccent.rules)
> , does not contain these Japanese characters, thus its unable to remove
> the diacritic signs. Can someone please guide when we can expect these
> Japanese characters will be added.
unaccent.rules, as distributed, is just an example. It is not meant
to be exhaustive or authoritative. Feel free to add your own entries
to your copy.
regards, tom lane