From: | "Atesz" <atesz(at)ritek(dot)hu> |
---|---|
To: | <pgsql-performance(at)postgresql(dot)org> |
Subject: | Re: planner/optimizer question |
Date: | 2004-04-27 12:54:27 |
Message-ID: | 002901c42c56$c8e077a0$0b02010a@atesz |
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Thread: | |
Lists: | pgsql-performance |
Hi,
You should try the next queries:
select support_person_id from ticket_crm_map where crm_id = 7 GROUP BY
support_person_id;
select support_person_id from ticket_crm_map where crm_id = 1 GROUP BY
support_person_id;
It can use the 'ticket_crm_map_crm_id_suppid' index.
Generally the Postgres use an k-column index if columns of your
conditions are prefix of the index column.
For example:
CREATE INDEX test_idx on test(col1,col2,col3,col4);
SELECT * FROM test WHERE col1=3 AND col2=13; -- This can use the index.
But the next queries cannot use the index:
SELECT * FROM test WHERE col1=3 AND col3=13;.
SELECT * FROM test WHERE col2=3;
If you have problem with seq_scan or sort, you can disable globally and
locally:
SET enable_seqscan=0;
SET enable_sort = 0;
Regards, Antal Attila
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