From: | Stéphane COEZ <scoez(at)harrysoftware(dot)com> |
---|---|
To: | "'John Arbash Meinel'" <john(at)arbash-meinel(dot)com> |
Cc: | <pgsql-performance(at)postgresql(dot)org> |
Subject: | Re: Performance pb vs SQLServer. |
Date: | 2005-08-15 09:05:11 |
Message-ID: | 20050815090515.0D75E100008F@mwinf0703.wanadoo.fr |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-performance |
John Arbash Meinel wrote :
>
> You might also try a different query, something like:
>
> SELECT DISTINCT cod FROM mytable ORDER BY cod GROUP BY cod;
> (You may or may not want order by, or group by, try the different
> combinations.)
> It might be possible to have the planner realize that all you
> want is unique rows, just doing a group by doesn't give you that.
>
> John
> =:->
>
Thanks John, but using SELECT DISTINCT with or without Order nor Group by is
worth...
30 sec (with index) - stopped at 200 sec without index...
So Hash Aggregate is much better than index scan ...
> >
> >Thanks for help.
> >
> >Stéphane COEZ
> >
> >
> >
> >
> >---------------------------(end of
> >broadcast)---------------------------
> >TIP 9: In versions below 8.0, the planner will ignore your desire to
> > choose an index scan if your joining column's datatypes do not
> > match
> >
> >
> >
>
>
>
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