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Re: why is bitmap index chosen for this query?

From: Stephen Byers <stephenabyers(at)yahoo(dot)com>
To: "Steinar H(dot) Gunderson" <sgunderson(at)bigfoot(dot)com>, pgsql-performance(at)postgresql(dot)org
Subject: Re: why is bitmap index chosen for this query?
Date: 2006-05-18 16:41:23
Message-ID: 20060518164123.98856.qmail@web30710.mail.mud.yahoo.com (view raw or flat)
Thread:
Lists: pgsql-performance
"Steinar H. Gunderson" <sgunderson(at)bigfoot(dot)com> wrote:  
It sounds like PostgreSQL badly overestimates the cost of the index scan.
Does the table perchance fit completely into memory, without
effective_cache_size indicating that?

  Don't know the exact way to answer your question, but my initial instinct is "no way."
    select pg_relation_size('packets');
   pg_relation_size 
------------------
      19440115712

  19GB.  So it's a big table.  The query I submitted earlier returns about 13M rows and the table currently has about 38M rows.
   
   

		
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