Re: Queries with large ResultSets

Alle 18:01, giovedì 20 maggio 2004, Kris Jurka ha scritto:
> On Wed, 19 May 2004, Jack Orenstein wrote:
> > If I'm reading the source code correctly, the PostgreSQL 7.3.4 JDBC
> > driver creates a ResultSet by evaluating the entire query, and putting
> > all the rows into a Vector. ResultSet.next() iterates over the
> > Vector. Is that in fact what is happening?
>
> Yes, in the 7.3 driver. The 7.4 driver (which works quite well against a
> 7.3 database) will use a cursor based fetch to retrieve a chunk of rows at
> a time. There are a number of restrictions required to be able to use
> this method (It only works with autocommit off and FORWARD_ONLY result
> sets). To enable this use Statement.setFetchSize to indicate how many
> rows at a time you want retrieved. Also there is a patch to the 7.5
> driver to be able to retrieve subsets of the resultset for the scrollable
> variety and hopefully I should get that in soon.

Ugh... those limitation are really frightening, this means we cannot fetch
big quantities of data outside of a transaction... this is a problem with
application servers like GeoServer that keep a connection pool and
need to fetch big quantities of data also outside a transaction... any hope
to see this fixed soon? Is it a driver problem or a server limitation?

Best regards
Andrea Aime