From: Jim C. Nasby <jnasby@pervasive.com>
To: Svenne Krap <svenne@krap.dk>
Cc: pgsql-performance@postgresql.org
Subject: Re: Performance problems with multiple layers of functions
Date: Fri, 24 Mar 2006 06:59:19 -0600
Message-ID: <20060324125919.GD90527@pervasive.com> (raw)
In-Reply-To: <4423EACD.80706@krap.dk>
References: <4423EACD.80706@krap.dk>
On Fri, Mar 24, 2006 at 01:49:17PM +0100, Svenne Krap wrote:
> explain select dataset_id, entity, sum(amount) from entrydata_current
> where flow_direction in (select * from outflow_direction(dataset_id))
> and dataset_id in (select * from get_dataset_ids(122)) group by
> dataset_id, entity;
<snip>
> which does not return within 10 minutes - which is unacceptable.
The issue is that the planner has no way to know what's comming back
from get_dataset_ids.
I think your best bet will be to wrap that select into it's own function
and have that function prepare the query statement, going back to
hard-coded values. So you could do something like:
SQL := 'SELECT ... AND dataset_id IN (''' || get_dataset_ids(122) ||
''');' (yeah, I know that won't work as written, but you get the idea).
--
Jim C. Nasby, Sr. Engineering Consultant jnasby@pervasive.com
Pervasive Software http://pervasive.com work: 512-231-6117
vcard: http://jim.nasby.net/pervasive.vcf cell: 512-569-9461
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To: pgsql-performance@postgresql.org
Cc: jnasby@pervasive.com, svenne@krap.dk
Subject: Re: Performance problems with multiple layers of functions
In-Reply-To: <20060324125919.GD90527@pervasive.com>
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