Re: How to change query planner configuration paramerters

From: Craig Ringer <ringerc(at)ringerc(dot)id(dot)au>
To: Melaka Gunasekara <donmelaka(at)gmail(dot)com>
Cc: Raghavendra <raghavendra(dot)rao(at)enterprisedb(dot)com>, pgsql-admin(at)postgresql(dot)org
Subject: Re: How to change query planner configuration paramerters
Date: 2011-09-18 10:43:57
Message-ID: 4E75CB6D.9000302@ringerc.id.au
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On 18/09/2011 5:51 PM, Melaka Gunasekara wrote:
> Merge Full Join (cost=10000000074.40..10000000093.69 rows=1159 width=286)

> Can you suggest why the merge join is being suggested when I have
> turned it off ?
>

AFAIK SETting a join type to "off" really just increases the cost
estimate so high that the planner will avoid using it where it has any
alternative. In this case, it doesn't seem to think it has any other way
to execute the query, or it thinks that any other way will be so
incredibly, insanely slow that the merge join is still better.

--
Craig Ringer

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