philippe wrote:
explain analyse
select count(*) from client_contact
left join client_company using(cli_id)
where (cli_mail = '[EMAIL PROTECTED]') OR
(lower(cli_nom) = 'xxxxxx' and zipcode = '10001');
QUERY PLAN
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Aggregate (cost=37523.98..37523.99 rows=1 width=0) (actual
time=3871.086..3871.087 rows=1 loops=1)
-> Merge Left Join (cost=0.00..36719.10 rows=321952 width=0) (actual
time=3871.058..3871.058 rows=0 loops=1)
This is the root of the problem - it's expecting to match over 320000
rows rather than 0.
I'm guessing there's a lot of correlation between cli_mail and cli_nom
(you're expecting them to match the same clients) but the planner
doesn't know this.
If this is a common query, you could try an index on zipcode - that
might cut down the other side.
However, I have to ask why you're using a left-join? Do you really have
rows in client_contact without a matching cli_id in client_company?
--
Richard Huxton
Archonet Ltd
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TIP 6: explain analyze is your friend
