Message-ID: <42FBCF4D.6060002@comcast.net>
Date: Thu, 11 Aug 2005 18:21:01 -0400
From: Jeffrey Tenny <jeffrey.tenny@comcast.net>
User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7) Gecko/20040616
MIME-Version: 1.0
To: pgsql-performance@postgresql.org
Subject: Mostly read performance
Content-Type: text/plain; charset=us-ascii; format=flowed
Content-Transfer-Encoding: 7bit

I have a largely table-append-only application where most transactions 
are read-intensive and many are read-only.  The transactions may span 
many tables, and in some cases might need to pull 70 MB of data out of a 
couple of the larger tables.


In 7.3, I don't seem to see any file system or other caching that helps 
with repeated reads of the 70MB of data.  Secondary fetches are pretty 
much as slow as the first fetch. (The 70MB in this example might take 
place via 2000 calls to a parameterized statement via JDBC).

Were there changes after 7.3 w.r.t. caching of data? I read this list 
and see people saying that 8.0 will use the native file system cache to 
good effect.  Is this true? Is it supposed to work with 7.3?  Is there 
something I need to do to get postgresql to take advatage of large ram 
systems?

Thanks for any advice.