Re: Trigram (pg_trgm) GIN index not used

On Thu, Feb 21, 2013 at 9:57 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Ivan Voras <ivoras@freebsd.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%'.

hm, one more data point that citext implementation didn't succeed in
terms of abstracting you from case sensitivity issues.

merlin