我有多个RETURN QUERY
语句的功能。最后,我只想获得N
随机记录。如果我在最后设置LIMIT max_size
每个RETURN QUERY
语句,我会得到max_size
*RETURN QUERY
次数。
我的功能的简短版本:
CREATE OR REPLACE FUNCTION android_getproposedsongs_test(
IN puserid character varying, max_size int)
RETURNS TABLE(sid uuid, method text) AS
$BODY$
DECLARE
songCount int;
BEGIN
RETURN QUERY
SELECT trackid as sid, lower('popular') as method
FROM ratingrecord
WHERE trackid NOT IN (
SELECT trackid FROM ratingrecord WHERE userid = puserid)
AND ratingrecord.rating > 0
GROUP BY trackid
HAVING SUM(rating) > 0
ORDER BY SUM(rating) DESC
LIMIT max_size;
CREATE TEMP TABLE recommended ON COMMIT DROP
AS
SELECT trackid, lower('recommended')
FROM ratingrecord finalRate
INNER JOIN
(
SELECT otherRate.userid AS otherUserId
, SUM(myRate.rating * otherRate.rating) as SumRating
FROM ratingrecord AS myRate
INNER JOIN ratingrecord AS otherRate
ON myRate.trackid = otherRate.trackid
WHERE myRate.userid = puserid AND myRate.userid != otherRate.userid
GROUP BY otherRate.userid
HAVING SUM(myRate.rating * otherRate.rating) > 0
) AS userRelations
ON finalRate.userid = userRelations.otherUserId
WHERE finalRate.trackid NOT IN (SELECT trackid FROM ratingrecord WHERE userid = puserid)
GROUP BY finalRate.trackid
HAVING SUM(finalRate.rating * userRelations.SumRating) > 0
ORDER BY SUM(finalRate.rating * userRelations.SumRating) DESC
LIMIT max_size;
RETURN QUERY SELECT * FROM recommended;
-- another RETURN QUERY statements
END;
$BODY$
LANGUAGE plpgsql VOLATILE;
我想要类似ORDER BY random() LIMIT max_size
结果集的东西,但不知道放在哪里。