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Re: Very high effective_cache_size == worse performance?

From: "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
To: "Robert Haas" <robertmhaas(at)gmail(dot)com>, "David Kerr" <dmk(at)mr-paradox(dot)net>
Cc: <pgsql-performance(at)postgresql(dot)org>
Subject: Re: Very high effective_cache_size == worse performance?
Date: 2010-04-20 18:17:02
Message-ID: 4BCDA94E0200002500030BF8@gw.wicourts.gov (view raw or flat)
Thread:
Lists: pgsql-performance
David Kerr <dmk(at)mr-paradox(dot)net> wrote:
 
> Incidentally the code is written to work like this :
> 
> while (read X lines in file){
> Process those lines.
> write lines to DB.
> }
 
Unless you're selecting from multiple database tables in one query,
effective_cache_size shouldn't make any difference.  There's
probably some other reason for the difference.
 
A couple wild shots in the dark:
 
Any chance the source files were cached the second time, but not the
first?
 
Do you have a large checkpoint_segments setting, and did the second
run without a new initdb?
 
-Kevin

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