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Re: merge join killing performance

From: Matthew Wakeling <matthew(at)flymine(dot)org>
To: Scott Marlowe <scott(dot)marlowe(at)gmail(dot)com>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: merge join killing performance
Date: 2010-05-19 03:00:18
Message-ID: alpine.DEB.2.00.1005182254110.1867@aragorn.flymine.org (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-performance
On Tue, 18 May 2010, Scott Marlowe wrote:
> Aggregate  (cost=902.41..902.42 rows=1 width=4)
>   ->  Merge Join  (cost=869.97..902.40 rows=1 width=4)
>         Merge Cond: (f.eid = ev.eid)
>         ->  Index Scan using files_eid_idx on files f
> (cost=0.00..157830.39 rows=3769434 width=8)

Okay, that's weird. How is the cost of the merge join only 902, when the 
cost of one of the branches 157830, when there is no LIMIT?

Are the statistics up to date?

Matthew

-- 
 As you approach the airport, you see a sign saying "Beware - low
 flying airplanes". There's not a lot you can do about that. Take 
 your hat off?                                  -- Michael Flanders

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