about the subselect query

Thanks to everyone who replied to my email about a
subselect query that was rather slow (1-3mins). The query is:

SELECT *
FROM items
WHERE package IN
(SELECT package
FROM items
WHERE ...user search expression...
GROUP BY package)

The fastest query I could come up with that is equivalent
to the one above is

SELECT DISTINCT i1.*
FROM items i1, items i2
WHERE i1.package = i2.package
AND ...user search expression...

which finishes in about 3s. EXPLAIN gives the following info on
the query (if "search expression" is a regexp on non-indexed
column i1.performer):

Unique (cost=1334.61 rows=2 width=151)
-> Sort (cost=1334.61 rows=2 width=151)
-> Nested Loop (cost=1334.61 rows=2 width=151)
-> Seq Scan on items i2 (cost=1332.56 rows=1 width=12)
-> Index Scan using items_packages on items i1
(cost=2.05 rows=12805 width=139)

But it is still faster if I run N+1 queries - first one SELECT
query to list packages, then another SELECT for each row in
the result.

Oskar Liljeblad (osk(at)hem(dot)passagen(dot)se)