Re: [pg_trgm] Making similarity(?, ?) < ? use an index

Artur, no worries, I'm not writing any code ;-)

I did the following:

CREATE TYPE trgm_match AS (match TEXT, threshold NUMERIC);
CREATE OR REPLACE FUNCTION trgm_check_match (string TEXT, match trgm_match)
RETURNS bool
AS 'SELECT match.match <-> string <= 1 - match.threshold'
LANGUAGE SQL;
CREATE OPERATOR %(leftarg = text, rightarg = trgm_match,
procedure=trgm_check_match);

This allows me to write:

SELECT ('Warsaw' % row('Warsw', 0.3)::trgm_match);

I'm not sure how to make this operator use an index. It seems I need to
create an operator class but I'm not sure how. This is how pg_trgm creates
its operator class:

-- create the operator class for gist
CREATE OPERATOR CLASS gist_trgm_ops
FOR TYPE text USING gist
AS
OPERATOR 1 % (text, text),
FUNCTION 1 gtrgm_consistent (internal, text, smallint,
oid, internal),
FUNCTION 2 gtrgm_union (internal, internal),
FUNCTION 3 gtrgm_compress (internal),
FUNCTION 4 gtrgm_decompress (internal),
FUNCTION 5 gtrgm_penalty (internal, internal,
internal),
FUNCTION 6 gtrgm_picksplit (internal, internal),
FUNCTION 7 gtrgm_same (gtrgm, gtrgm, internal),
STORAGE gtrgm;

Should my operator class mimic the one above?
--
Greg Navis
I help tech companies to scale Heroku-hosted Rails apps.
Free, biweekly scalability newsletter for SaaS CEOs
<http://www.gregnavis.com/newsletter/>