Re: Alternative to INTERSECT

On Tue, 31 Jul 2007 17:30:51 +0000
Andreas Joseph Krogh <andreak(at)officenet(dot)no> wrote:

> Hi all. I have the following schema:
>
> CREATE TABLE test (
> id integer NOT NULL,
> field character varying NOT NULL,
> value character varying NOT NULL
> );
>
> ALTER TABLE ONLY test
> ADD CONSTRAINT test_id_key UNIQUE (id, field, value);
>
> CREATE INDEX test_like_idx ON test USING btree (id, field, value
> varchar_pattern_ops);
>
> Using INTERSECT I want to retrieve the rows matching (pseudo-code)
> "firstname LIKE ('andrea%' OR 'jose%') AND lastname LIKE 'kro%'"

Why not:

WHERE (t.field = lastname AND t.value LIKE 'kro%')
OR (t.field = firsname AND (
t.value LIKE 'jose%' OR t.value LIKE 'andrea%')
)

Not tested. If you're having performance problems is probably less
like that the INTERSECT is the problem with all those LIKE's in
there? Is t.value indexed?

Josh