On 4/23/07, Marco Bambini <[EMAIL PROTECTED]> wrote:
As a performance test I created a db with 300,000 records, table is:
CREATE TABLE table1 (a INTEGER, b INTEGER)
a query like:
SELECT * FROM table1 WHERE a=5 AND b=11;
takes 0.281 secs.
if I add two indexes:
CREATE INDEX index1 ON table1(a);
CREATE INDEX index2 ON table1(b);
the same query is about two times slower, it takes 0.463 secs.
(I know that only one index is used by the query).
Try
CREATE INDEX index_ab ON table1 (a, b);
and test.
I repeated the test several times and results are confirmed...
Anyone have an explanation?
---
Marco Bambini
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Nelson Inst. for Env. Studies, UW-Madison http://www.nelson.wisc.edu/
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