Re: streaming result sets: progress

From: Nic Ferrier <nferrier(at)tapsellferrier(dot)co(dot)uk>
To: Scott Lamb <slamb(at)slamb(dot)org>
Cc: pgsql-jdbc(at)postgresql(dot)org
Subject: Re: streaming result sets: progress
Date: 2002-11-22 15:15:18
Message-ID: 8765up7i0p.fsf@pooh-sticks-bridge.tapsellferrier.co.uk
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Whoa! big time over run... anyway, getting back to this:

Scott Lamb <slamb(at)slamb(dot)org> writes:

> Nic Ferrier wrote:
>
> > Thomas O'Dowd writes:
> >
> >
> > >>3) I think the transaction characteristics of the current patch are just
> > >>fine and conform to the jdbc specification. The code should
> > >>automatically close the resultset when a commit occurs. One thing that
> > >>will be confusing is that noncursor based result sets will work accross
> > >>commits, but cursor based ones won't. But I think that is reasonable.
> > >
> > >Sounds reasonable to me as long as its clear to the programmer what type
> > >they are using. I definitely don't want to see the noncursor based
> > >resultsets closed, but I can't see a better solution for cursor based
> > >ones...
> >
> >
> > How can we make clear what type of ResultSet is being used?
>
> I suggest with ResultSet.CLOSE_CURSORS_AT_COMMIT (cursor method) vs
> ResultSet.HOLD_CURSORS_OVER_COMMIT (old method). You can both request a
> certain type when you create a Statement or PreparedStatement and get
> the type of the resultset from the Statement or PreparedStatement.

So what you're saying is that this code:

Statement st
= connection.createStatement(ResultSet.CLOSE_CURSORS_AT_COMMIT,
ResulSet.CONCUR_READ_ONLY);
ResultSet rs = st.executeQuery("select * from table");

would produce a cursor based res set whereas:

Statement st = connection.createStatement();
ResultSet rs = st.executeQuery("select * from table");

would not.

That would mean that we didn't need the fetch size signal. Or we
could use the fetchSize signal as well.

Note also that CLOSE_CURSORS_AT_COMMIT is not actually a result set
type so it _might_ break other code.

Anyone else have any opinion on this?

Nic

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