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From: twoflower <standa.kurik@gmail.com>
To: pgsql-performance@postgresql.org
Subject: Re:  Re: Query > 1000× slowdown after adding datetime comparison
Date: Tue, 1 Sep 2015 02:51:50 -0700 (MST)
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林士博 wrote
> I think you should try putting the precomputed boolean temp_eval column
> to "EXTERNAL_TRANSLATION" r table.
> 
> And if possible, try creating a conditional index on id where temp_eval is
> true,
> on "EXTERNAL_TRANSLATION" r table.
> 
> So that, only check this index can get the top 1000 records.

I agree that might help. But I would still like to understand what's the
reason for difference between the second and the third query. Both contain a
simple <column> = <constant> expression, yet one finishes immediately and
one runs for 41 minutes.




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