From: | ddd(at)genesis(dot)homeip(dot)net |
---|---|
To: | pgsql-general(at)hub(dot)org |
Subject: | Re: Am I really stupid??? |
Date: | 2000-05-19 02:03:49 |
Message-ID: | SAK.2000.05.19.cmpdloos@ddd |
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Thread: | |
Lists: | pgsql-general |
>> Does that mean for two tables, one 1000 rows another 2000 rows, it's a
>> total of 1000 X 2000 rows scanned?
>
>You got it :-(. (Unless we find what we're looking for before scanning
>all the way through --- so M*N is the worst case, but the average case
>is probably less.)
>
>> I suppose one way to slightly reduce the number of rows would be to select
>> stuff into temp tables first.
>
>7.0 is smart enough to do that if the inner query looks complicated.
>If it's just a sequential scan itself, then of course there's no win...
Ok I got it. I'm going to do simple selects and doing the intersects myself :)
Dragos.
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