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Cannot interpret EXPLAIN

From: Jörg Kiegeland <kiegeland(at)ikv(dot)de>
To: pgsql-performance(at)postgresql(dot)org
Subject: Cannot interpret EXPLAIN
Date: 2009-02-17 14:33:40
Message-ID: 499ACAC4.8010608@ikv.de (view raw or flat)
Thread:
Lists: pgsql-performance
Hi,

I have a query  SELECT * FROM myTable WHERE ((myCol = var1) OR (myCol = 
var2))

.. which produces the following EXLAIN output:


Index Scan using myIndex on myTable (cost=0.00..8.28 rows=1 width=537)
  Filter: ((myCol = $1) OR (myCol = $2))


The index "myIndex" is an index on column "myCol". However I expected an 
"Index Cond:" row instead of a "Filter:" row, which normally indicates 
performance problems.
Should I rather split the OR and use two SELECT statements to get my 
result (var1!=var2)? Namely in this case, "Index Cond:" is outputed by 
EXPLAIN.

--Jörg Kiegeland

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Next:From: Tom LaneDate: 2009-02-17 15:53:39
Subject: Re: Query composite index range in an efficient way
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Subject: Re: suggestions for postgresql setup on Dell 2950 , PERC6i controller

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