View in subquery too slow

Question

Hi!
On Oracle 11.2
SELECT a.*
FROM APPLES a
LEFT OUTER JOIN PROPERTIES p on a.id=p.apple_id
WHERE
a.type = '1'
AND 0< (SELECT count(*) FROM view_1 v WHERE v.foo=123 AND v.color = p.color)This is 3 or more times slower (0.20 versus 0.60 seconds in one test) on our system than this:
DELETE from table_1;
INSERT INTO table_1 SELECT * FROM view_1 v WHERE v.foo=123;
SELECT a.*
FROM APPLES a
LEFT OUTER JOIN PROPERTIES p on a.id=p.apple_id
WHERE
a.type = '1'
AND 0< (SELECT count(*) FROM table_1 v WHERE v.foo=123 AND v.color = p.color)Is there a way to speed up the view?
It seems a temporary table would help. Is there some hint for Oracle to use it? Without changing each query?
The view_1 is a join over 4 tables and 3 more views (which are a CONNECT BY over a single table).
I thought about materialized views, but they either:
- slow down commits (ON COMMIT refresh)
- or are not up to date (scheduled refresh)
Regards,
David

Answer 1

I would move the properties table into the subquery. And of cause you MUST use exists instead of the slow count.
example
SELECT a.*
FROM APPLES a
WHERE a.type = '1'
AND EXISTS (SELECT null
                     FROM PROPERTIES p
                     join view_1 v on v.color = p.color)
                     where a.id=p.apple_id
                     and v.foo=123)
;THis query is not identical to the original. It would return only ONE row if you have multiple properties for the same apple.
Your query would return one identical apple row for each property.
However I guess since you don't even show the different properties, this is really what you want.
Edited by: Sven W. on Aug 4, 2011 6:47 PM