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Re: Merge Join vs Nested Loop

From: Scott Marlowe <smarlowe(at)g2switchworks(dot)com>
To: Tobias Brox <tobias(at)nordicbet(dot)com>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-performance(at)postgresql(dot)org
Subject: Re: Merge Join vs Nested Loop
Date: 2006-09-27 15:19:24
Message-ID: 1159370365.4643.7.camel@localhost.localdomain (view raw or flat)
Thread:
Lists: pgsql-performance
On Wed, 2006-09-27 at 17:05 +0200, Tobias Brox wrote:
> [Scott Marlowe - Wed at 09:58:30AM -0500]
> > Have you tried chaning the cpu_* cost options to see how they affect
> > merge versus nested loop?
> 
> As said in the original post, increasing any of them shifts the planner
> towards nested loops instead of merge_join.  I didn't check which one of
> the cost constants made the most impact.

So, by decreasing them, you should move away from nested loops then,
right?  Has that not worked for some reason?

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