ResultSet iterations duration

[Jérôme <je...@unicaen.fr>]

Hi all,

I am currently working with Jena and Fuseki. My web application queries 
the remote fuseki server with a
"QueryExecutionFactory.sparqlService(url, query)" call.

The server answers quickly, but the resultSet iteration is really slow.


             QueryExecution qExec = 
QueryExecutionFactory.sparqlService(url, query);
             ResultSet set = qExec.execSelect();
             log.info("start");
             while (set.hasNext()) {
                 set.next();
             }
             log.info("done");

between 2 and 6 seconds from "start" to "done".

1-Why is it so long? How can i boost it?
2-Is there a way to know the number of solutions without iterate over 
the resultSet?

Thanks.

Jérôme.

Re: ResultSet iterations duration

[Andy Seaborne <an...@apache.org>]

On 05/10/11 15:25, Jérôme wrote:
> Hi all,
>
> I am currently working with Jena and Fuseki. My web application queries
> the remote fuseki server with a
> "QueryExecutionFactory.sparqlService(url, query)" call.
>
> The server answers quickly, but the resultSet iteration is really slow.
>
>
> QueryExecution qExec = QueryExecutionFactory.sparqlService(url, query);
> ResultSet set = qExec.execSelect();

This sets things up and connects to the server - it does not recieve all 
the results.

> log.info("start");
> while (set.hasNext()) {

This receives a result.

Underlying network buffers bytes.

> set.next();
> }
> log.info("done");
>
> between 2 and 6 seconds from "start" to "done".
>
> 1-Why is it so long? How can i boost it?

I guess the query is expensive in some way - what is the query? how much 
data?

> 2-Is there a way to know the number of solutions without iterate over
> the resultSet?

ARQ is a streaming results system unless you want to do something 
different.  Counting needs to walk over the results (especially in the 
case of a remote execution).

Force the results to be collected with ResultSetFactory.makeRewindable 
and you can count them or print them, and reset the result set.

	Andy

>
> Thanks.
>
> Jérôme.
>