From: | Ivan Sergio Borgonovo <mail(at)webthatworks(dot)it> |
---|---|
To: | pgsql-general(at)postgresql(dot)org |
Subject: | limit and other joined tables |
Date: | 2009-01-13 12:01:13 |
Message-ID: | 20090113130113.6ba7e51a@dawn.webthatworks.it |
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Lists: | pgsql-general |
Is the planner/optimiser smart enough to join just after the LIMIT
in a similar situation:
select [columns from A, B and C] from A
join B on A.Aid=B.Bid
join C on A.Aid=C.Cid
where (conditions on A and B columns)
order by [columns from A and B]
limit 10;
What about a similar situation with subselects?
select [columns from A, B, C] from (
select [column from A, B]
where (conditions on A and B columns)
) s
join C on s.Aid=C.Cid
order by [columns from A, B]
limit 10;
vs
select [columns from A, B, C] from (
select [column from A, B]
order by [columns from A, B]
limit 10
) s
join C on s.Aid=C.Cid;
Can postgresql take advantage of the LIMIT even if it is in the
outer select?
--
Ivan Sergio Borgonovo
http://www.webthatworks.it
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