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Re: about libpq-C FETCH ALL performance issue

From: "Jeroen T(dot) Vermeulen" <jtv(at)xs4all(dot)nl>
To: jing han <jing_han_66(at)yahoo(dot)com>
Cc: pgsql-interfaces(at)postgresql(dot)org
Subject: Re: about libpq-C FETCH ALL performance issue
Date: 2004-11-15 14:24:52
Message-ID: 20041115142452.GF90696@xs4all.nl (view raw or flat)
Thread:
Lists: pgsql-interfaces
On Mon, Nov 15, 2004 at 05:55:01AM -0800, jing han wrote:
 
> 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 

If you use just the FETCH ALL, why are you using a cursor in the first
place?


> Then I try FETCH 1 instead of FETCH ALL, no
> improvement.
 
Are you doing just one FETCH 1 to obtain a single row, or are you
doing the FETCH 1 in a loop so you get all rows?  The latter would
be extremely slow in any case...  Try fetching smaller blocks, like
maybe 100 rows at a time, and see if that helps.


> 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 or new release to work better?

Just do a normal "SELECT" without the cursor.  This will give you
all the data at once, just like a FETCH ALL.


Jeroen


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