[Qgis-developer] memory layer performance while adding many features?

[Raymond Nijssen]

Dear developers, ;)

A plugin of mine imports data from a gml file into a memory layer. Works 
fine for tiny gml files, but takes forever on huge ones. Sounds 
plausible maybe, but the relation is not linear.

So I did did some tests and found out that reading and parsing the gml 
and creating the features always goes at the same speed of about 400 
features a second (fps). But when adding these to my memory layer, the 
process slows down tremendously.

I output the fps for every 1000 features and it gave me this graph:

http://terglobo.nl/downloads/memory-layer-performance.png

At the end of the importing process I'm processing just 3 features per 
second.

Is this expected behaviour? Is a memory layer not meant for something 
like this? Or is this a bug?

In the source code I found that for every feature I add to a memory 
layer the index is updated. Could that be inefficient?

Hoping anyone can explain!

Regards,
Raymond


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