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Date: Mon, 24 Mar 2014 09:08:46 +0200
From: Heikki Linnakangas <hlinnakangas@vmware.com>
Organization: VMware
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To: Erik van Zijst <erik.van.zijst@gmail.com>
CC: pgsql-performance@postgresql.org
Subject: Re: Suboptimal query plan when using expensive BCRYPT functions
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On 03/22/2014 02:59 AM, Erik van Zijst wrote:
> Is there any way I can get postgres to perform the hash calculations
> on the *result* of the other parts of the where clause, instead of the
> other way around? Or else rewrite the query?

The planner doesn't know that the crypt function is expensive. That can 
be fixed with "ALTER FUNCTION crypt(text, text) COST <high value>". Even 
with that, I'm not sure if the planner is smart enough to optimize the 
query the way you'd want, but it's worth a try.

- Heikki


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