On Sat, Oct 27, 2012 at 11:16 AM, Sandro Santilli <[email protected]> wrote: > On Sat, Oct 27, 2012 at 01:41:49AM +0200, Tim Sutton wrote: > >> * One of the major limitations I and the many people that contact me >> about QGIS experience is lack of performance. Just yesterday I got an >> email from someone in Sudan trying to use QGIS to work with ~300 000 >> point records and it taking 4 hours to do some simple operations on >> the dataset. > > I think such cases should be handled by only fetching a sample of the > data for visualization purpose, rather than the full set. And similarly > only a subset of vertices could be fetched when facing dense vectors. > > This is something that might need an API change too, as you would need > the providers to be told when the data has to be fetched only for > visualization (thus generalization is possible) or for editing (thus > you want all the data, possibly forcing a restriction on extent).
The changes on the branch make adding such improvement possible: requests are encapsulated into QgsFeatureRequest class, so the generalization could be implemented with a new flag within that class - some providers could support it, some would just ignore it (or fetch all vertices and let GEOS simplify the geometry before rendering). Martin _______________________________________________ Qgis-developer mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/qgis-developer
