XML parsing slows down WFS and GML loading

[pcav]

WFS loading is very slow: I always thought that was due to bandwidth, but now it seems more likely that XML parsing is the culprit (thanks Furieri for noticing!). The same can be see in GML loading from local file. The effect seems particularly heavy on Windows.

[mhugent]

Is there a test server instance / test file? The WFS provider uses a different approach than the GML reader of OGR. So probably they are slow for different reasons. And yes, reading XML is more demanding performance wise than reading the same information in a binary format.

[pcav]

This should be a good and fast server, rather slow to download:

​http://webgis.regione.sardegna.it/geoserver/wfs?

[pcav]

While loading, the bottleneck seems CPU, that goes up (98-99%)

[mhugent]

I tested it with the layer ras:IDT_MN11V_DATI_AGGR_PROV. (22MB) with wget and the WFS plugin. I didn't measure the time exactly, but it seemed comparable to me, appr. 60 - 70 seconds.

The reason the CPU works while loading is that the WFS provider does asynchronous request and starts parsing before the whole document has arrived.

[pcav]

So better close it - still unsure about GML though, but this will require more testing, especially on Windows.