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Re: JDBC and processing large numbers of rows

From: Dave Cramer <pg(at)fastcrypt(dot)com>
To: David Wall <d(dot)wall(at)computer(dot)org>
Cc: "pgsql-jdbc(at)postgresql(dot)org" <pgsql-jdbc(at)postgresql(dot)org>
Subject: Re: JDBC and processing large numbers of rows
Date: 2004-05-11 22:51:08
Message-ID: 1084315868.1536.132.camel@localhost.localdomain (view raw, whole thread or download thread mbox)
Lists: pgsql-jdbc
Well, if all else fails you may have to write a wrapper around them to
deal with the discrepancies between oracle and postgres.

One thing though, be warned holdable cursors in postgres have to be
materialized, so you may end up running out of server memory. This means
that you need to be inside a transaction to get a non-holdable cursor.


On Tue, 2004-05-11 at 16:32, David Wall wrote:
> > Use cursors to page through really large result sets
> Well, I've thought about that, but that just led me to my 3rd question in my
> previous inquiry:
> > > 3) How do people use cursors in JDBC?  Being able to FETCH seems like a
> nice
> > > way to handle question #2 above in a batch program, since only a subset
> of
> > > rows needs to be retrieved from the db at a time.  Cursors probably
> don't
> > > work for question #1 above since keeping a transaction alive across page
> > > views is generally frowned upon and even hard to accomplish since it
> means
> > > locking up a connection to the db for each paging user.
> The question for me is how do you portably use cursors so that you can work
> with Oracle and PG seamlessly?  I presume there might be some (hopefully)
> slight variations, like there are with BLOBs, but it would be nice if using
> cursors was standardized enough to make it using standard JDBC.
> It seems that the issues are with defining a cursor, executing it, fetching
> against it, then release it when done.  Is there a standard way to do this?
> Any examples?
> Thanks,
> David
> !DSPAM:40a138a962802251020430!
Dave Cramer
519 939 0336
ICQ # 14675561

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Subject: Re: Retrieve the postgres transaction id
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