Re: [gnome-db] Questions about a possible asynchronous gda behaviour

[Rodrigo Moya <rodrigo gnome-db org>]

On Tue, 2003-11-11 at 16:54, Gonzalo Paniagua Javier wrote:
> El mar, 11-11-2003 a las 12:50, David Marín Carreño escribió:
> > Hi.
> > 
> > I'd like to know what is the gda behaviour while querying a PostgreSQL
> > server. 
> > 
> > Is it asynchronous? That is: the query is launched with
> > "gda_connection_execute_single_command", but this function returns after
> > making the query, without waiting for the datamodel to be filled with
> > the real data. The application should block when trying to access to
> > datamodel rows not filled yet, and should unblock when these rows get
> > the real data.
> 
> No, it's not.
> 
it's not asynchronous, but rows are fetched on demand, when the app
requests them. So, when you execute a comand, you get the pointer to the
recordset, and the provider fetches the rows when requested, not in
advance.

> > 
> > I don't know if this is the actual behaviour, but if it isn't, IMHO, I
> > think it's a necessary feature: when a program has to show a very long
> > list of data, I cannot wait until having all the rows before starting to
> > show the first of them.
> > 
> > I know that PostgreSQL, with libpq, support this behaviour
> > (http://www.postgresql.org/docs/7.3/interactive/libpq-async.html), where
> > you make a query, and then ask libpq for data a lot of times until all
> > the data has been sent.
> 
> We may add an option to GdaCommandOptions that tells the provider we
> want async processing. Then we have to add a function to be called when
> the system is idle that reads any data available and stores it in the
> GdaDataModel you get. The connection is locked for anything else while
> this has not finished.
> 
hmm, IIRC, the postgres provider fetches the rows when it's requested to
do so, one by one. Or am I wrong Gonzalo?

cheers