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Fetch Sizes and Blocks

From: Ramesh Reddy <rareddy(at)redhat(dot)com>
To: pgsql-odbc(at)postgresql(dot)org
Subject: Fetch Sizes and Blocks
Date: 2011-06-16 21:07:59
Message-ID: 1308258479.15712.29.camel@localhost.localdomain (view raw or flat)
Thread:
Lists: pgsql-odbc
Hi,

I have been trying to read the code and understand how the results
fetching works in ODBC. It looks like by default, all tuples are
pre-fetched before they are returned to the client. Unless if you
specify

UseDeclareFetch=1
Fetch=1000

then it will use cursors to fetch 1000 rows at a time. 

My question is at network layer, does the driver fetch individual row at
a time from server (for pre-fetch or cursor), or does it use some kind
"bulk" fetch so that it minimizes the network traffic? I also did not
see "Fetch" value coming across as connection string at server side,
when it is set.

PS: we wrote a PG wire protocol over http://teiid.org and want improve
the performance.

Thank you.

Ramesh..




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