Hi Michaël, There are a couple of possibilities to improve the performance of operations in two ways (which both help here AFAICS)
* Give QgsExpression::prepare() more power * Compile functions (where possible) The send one depends to some degree on the first one. Let me know if you have sponsors, I've got some experimental code somewhere and I am very interested in working on this project. FYI, a first test - only the prepare part - some months ago improved the 2.5D rendering by ~30%. Regards Matthias On 07/05/2016 03:11 PM, kimaidou wrote: > Hi all, > > I am a bit curious about performances concerning the use of Spatial > expressions in QGIS, for example to select features like this > > intersects( > $geometry, > geom_from_wkt( 'MultiPolygon (((649308.28000000002793968 > 6978002.05999999959021807, 649295.32999999995809048 > 6977994.54999999981373549, 649235.92000000004190952 > 6978013.50999999977648258, 649182.53000000002793968 > 6978077.32000000029802322, 649212.34999999997671694 > 6978159.53000000026077032, 649308.28000000002793968 > 6978002.05999999959021807)))') > ) > > NB: I have simplified the WKT representation here > > I am running this expression inside QGIS 2.14, for a layer containing > approx. 100 000 features ( buildings). > The WKT polygon represents a very small area compared to the whole > layer: 500 features only are selected. > > It seems to me no spatial index is used, because it takes some time to > run ~ 3 minutes. > > I have checked the option to run expressions server side, and all the > layers are PostGIS layers. > > What could be done to improve this kind of expressions, which can be > used elsewhere in QGIS ( to toggle labels for example ) ? > > Regards > Michaël > > > _______________________________________________ > Qgis-developer mailing list > [email protected] > List info: http://lists.osgeo.org/mailman/listinfo/qgis-developer > Unsubscribe: http://lists.osgeo.org/mailman/listinfo/qgis-developer > _______________________________________________ Qgis-developer mailing list [email protected] List info: http://lists.osgeo.org/mailman/listinfo/qgis-developer Unsubscribe: http://lists.osgeo.org/mailman/listinfo/qgis-developer
