[Qgis-developer] slowness reading shp

[Giovanni Manghi]

Hi,


On Sat, 2011-02-19 at 08:18 +0100, Paolo Cavallini wrote:
> Il giorno ven, 18/02/2011 alle 23.58 +0100, Martin Dobias ha scritto: 
> > The main performance killer here is painting of borders. The layer is
> > rendered several times faster if you set border style to "no pen".
> 
> This has no noticeable effect in my case.


I made my own tests:

on trunk with a big 600mb (43000 features) polygon shapefile, the vector
opens in 32 seconds (new symbology, with borders, anti-aliasing
disabled).

After saving a style with no borders the shape opens in 15/16 seconds.

The problems remain in both cases when zooming/panning as there is
always a bigdelay and in between the program freezes (under Linux).

Opening the attribute table or toggling editing or selecting polygons is
a real pain.







> > The clear direction is to merge threading branch to trunk. It contains
> > some optimizations for rendering, plus it does not freeze while
> > rendering and continuously updates the map. So even when working with
> > huge layers, it's possible to see how rendering continues and zoom/pan
> > to desired region of interest without having to wait until rendering
> > of the last map finished.
> 
> Any idea about when it will be merged? Anyone working on this?
> What performance gain would you expect with threading?




I tested everything again after having compiled the threading branch.

The result is *much* better (with or without borders) when opening the
shape and panning/zooming, and looking at the way the geomteries are
painted in the canvas it seems to me that is the same approach used in
gvsig.

Editing/selecting is still painful (also in gvsig...).


Cheers


-- Giovanni --