From: jing han <jing_han_66@yahoo.com>
To: pgsql-interfaces@postgresql.org
Subject: about libpq-C FETCH performance issue
Date: Thu, 11 Nov 2004 09:00:50 -0800 (PST)
Message-ID: <20041111170050.75735.qmail@web53501.mail.yahoo.com> (raw)
Hello,
I'm working on a project where libpq-C is envolved. We
have several background processes keep querying
certain data from database to send out ip packets at
fast rate.
With libpq-C interface, I use
res = PQexec(conn, "DECLARE myportal CURSOR FOR select
* from ourTables");
and then res = PQexec(conn, "FETCH ALL in myportal");
to get the data.
I found when our database has more and more data, res
= PQexec(conn, "FETCH ALL in myportal"); cost more and
more time, much more than
res = PQexec(conn, "DECLARE myportal CURSOR FOR select
* from ourTables");
(note:ourTables can be several tables join together)
and make our sending packet rate extremely low. We get
into big problems here.
Then I try FETCH 1 instead of FETCH ALL, no
improvement.
All the queries our background processes use was
optimized with EXPLAIN utility, these queries take
much shorter time in postgres console.
So I wonder what FETCH statement is doing: just fetch
query results from cursor or do the real query, get
the query result and give these results to us. Why it
is much slower than console sql command?
I wonder if there is other faster way ( I mean other
than FETCH ALL command) to get data from database with
libpq-C, or If you have a patch to make FETCH work
faster?
Hope to hear from you soon.
Best Regards
jing
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To: pgsql-interfaces@postgresql.org
Cc: jing_han_66@yahoo.com
Subject: Re: about libpq-C FETCH performance issue
In-Reply-To: <20041111170050.75735.qmail@web53501.mail.yahoo.com>
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