On Mar 27, 2008, at 4:56 AM, shabda raaj wrote:
>
>>>> main_link = LinkVote.alias('main_link')
>>>> peer = LinkVote.alias('peer')
>>>> countr = LinkVote.alias('countr')
>>>> conn.execute(select([main_link.c.link_id, peer.c.link_id,
>>>> func.count(peer.c.user_id)/select([func.count(countr.c.id)],
>>>> countr.c.link_id == peer.c.link_id, correlate = peer).scalar()],
>>>> and_(peer.c.user_id == main_link.c.user_id, peer.c.direction ==
>>>> main_link.c.direction, main_link.c.link_id == 149), group_by =
>>>> peer.c.link_id, limit = 30))
>
Assume 0.4 usage here. The "scalar()" method there should be
"as_scalar()" - "scalar()" indicates you'd like to execute the query
immediately and return a single result. Also "correlate" is a boolean
argument, not a selectable, and is "True" by default in any case...its
a leftover from older versions of SA before we had the generative
"correlate()" method. If you want to set correlations explicitly, use
"select(...).correlate(peer)". But in this case its not needed since
the correlation is straightforward:
select([main_link.c.link_id, peer.c.link_id,
func.count(peer.c.user_id)/select([func.count(countr.c.id)],
countr.c.link_id == peer.c.link_id).as_scalar()],
and_(peer.c.user_id == main_link.c.user_id, peer.c.direction ==
main_link.c.direction, main_link.c.link_id == 149),
group_by = peer.c.link_id, limit = 30)
produces:
SELECT main_link.link_id, peer.link_id, count(peer.user_id) / (SELECT
count(countr.id) AS count_1
FROM news_linkvote AS countr
WHERE countr.link_id = peer.link_id) AS anon_1
FROM news_linkvote AS main_link, news_linkvote AS peer
WHERE peer.user_id = main_link.user_id AND peer.direction =
main_link.direction AND main_link.link_id = :main_link_link_id_1 GROUP
BY peer.link_id
LIMIT 30
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