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Re: planner/optimizer question

From: Jeff <threshar(at)torgo(dot)978(dot)org>
To: "Gary Doades" <gpd(at)gpdnet(dot)co(dot)uk>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: planner/optimizer question
Date: 2004-04-30 12:32:16
Message-ID: 69EF9EF2-9AA2-11D8-A4E1-000D9366F0C4@torgo.978.org (view raw or flat)
Thread:
Lists: pgsql-performance
On Apr 30, 2004, at 3:01 AM, Gary Doades wrote:

[ pg query plan, etc ]

I wonder if other parts of the plan are affecting the speed.

I've recently run into a case where a merge join plan was chosen for 
this query, which took 11 seconds to execute.  Forcing it to pick a 
nested loop join dropped it to 3.  (Updating my 
default_statistics_target to 500 caused the planner to choose nested 
loop join)

So, is the plan really the same?

  A better comparision query may be a simple "select a from mytable 
where a between foo and bar"  to get an index scan.  In that case its a 
straight up, vanilla index scan.  Nothing else getting in the way.

--
Jeff Trout <jeff(at)jefftrout(dot)com>
http://www.jefftrout.com/
http://www.stuarthamm.net/


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