Re: Trigram (pg_trgm) GIN index not used

Ivan Voras <ivoras(at)freebsd(dot)org> writes:
> I have a table with the following structure:
> ...
> raw_data | citext | not null
> ...
> "documents_raw_data_trgm" gin (raw_data gin_trgm_ops)

> I'd like to use pg_trgm for matching substrings case-insensitively, but
> it doesn't seem to use the index:

You're outsmarting yourself by using citext as the column datatype.
That causes "ilike" to be interpreted as a citext-specific operator,
which is not a member of the gin_trgm_ops operator class, so it doesn't
match this index.

I wonder whether we really need that citext-specific operator at all
... but in the meantime, if you need the column to be citext for some
other reason, I'd suggest making a gin index on raw_data::text and
then writing the query as raw_data::text ilike '%zagreb%'.

regards, tom lane