Jim C. Nasby wrote:
On Thu, Oct 19, 2006 at 06:19:16PM +0100, Richard Huxton wrote:
OK - these plans look about the same, but the time is greatly different.
Both have rows=140247 as the estimated number of rows in tbl_reg. Either
you have many more rows in the second case (in which case you're not
running ANALYSE enough) or you have lots of gaps in the table (you're
not running VACUUM enough).
Look closer... the actual stats show that the sorts in the second case
are returning far more rows. And yes, analyze probably needs to happen.
The results are different, I agree, but the plans (and estimates) are
the same. Given the deletes and inserts I wasn't sure whether this was
just lots more rows or a shift in values.
I'd then try putting an index on (attr1,attr2,attr3...attr6) and see if
that helps reduce time.
With bitmap index scans, I think it'd be much better to create 6 indexes
and see which ones actually get used (and then drop the others).
Good idea.
--
Richard Huxton
Archonet Ltd
