Re: why is bitmap index chosen for this query? - Mailing list pgsql-performance

From Stephen Byers
Subject Re: why is bitmap index chosen for this query?
Date
Msg-id 20060518164123.98856.qmail@web30710.mail.mud.yahoo.com
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In response to Re: why is bitmap index chosen for this query?  ("Steinar H. Gunderson" <sgunderson@bigfoot.com>)
Responses Re: why is bitmap index chosen for this query?
List pgsql-performance
"Steinar H. Gunderson" <sgunderson@bigfoot.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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