Re: [Tracker] Large sparql query results

["Spivak, Max" <spivak lab126 com>]

Thanks Philip and Zheng. I can make things work with limit and offset.

/// Max

On Mar 5, 2010, at 1:20 AM, Philip Van Hoof wrote:

> On Thu, 2010-03-04 at 22:07 -0500, Spivak, Max wrote:
>
> Hi Max,
>
> > I have a question about large query results from tracker-store. in my
> > experience with SQL databases and their client api, when a query
> > results are generated, only a subset are initially transferred to the
> > client. The rest are loaded on demand as the client iterates over the
> > results. 
>
> This usually only is the case when the client requests iterating over
> the result using a so called cursor.
>
> Usually are those cursors also one-direction only (you can't go back).
>
> Because SQLite isn't MVCC it would mean that for the whole duration that
> a client keeps such a cursor open, all other database connections will
> be more or less blocked from doing things.
>
> This is why we don't support a cursor API.
>
> You can emulate a cursor API with LIMIT and OFFSET, of course.
>
> > How does libtracker-client handle this? What if the result set is too
> > big to fit in the client memory? Is there any sort of incremental
> > result returning ability or callback support with partial results? t
>
> We at this moment don't provide this ourselves in libtracker-client.
>
> LibQtTracker has a "streaming model" which will do this for you on a
> QAbstractDataModel as far as I know.
>
> http://maemo.gitorious.org/maemo-af/libqttracker
>
>
> Cheers,
>
> Philip
>
> -- 
> Philip Van Hoof, freelance software developer
> home: me at pvanhoof dot be 
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