[QGIS-Developer] Qgis server: terrible performance with Qgis 3.26

[David Marteau]

Hi,

I have noticed a huge drop of performance while testing Qgis server with 
Qgis 3.26, from 10x to 30x slower as usual.

Trying to reduce the problem I have found a huge increase of time spend 
reading the project in 3.26 compared to 3.24.

Here some benchmark with very simple project from the test data set. 
Note: the project has been updated with qgis 3.26:

Qgis 3.24:
======

readflags = QgsProject.ReadFlags()readflags |= 
QgsProject.FlagTrustLayerMetadata

prj = QgsProject()

%timeit -n 1 prj.read(f"{datapath}/france_parts.qgs",readflags)

> 15.7 ms ± 205 µs per loop (mean ± std. dev. of 7 runs, 1 loop each)

Qgis 3.26:
======

readflags = QgsProject.ReadFlags() readflags |= 
QgsProject.FlagTrustLayerMetadata

​prj = QgsProject()

%timeit -n 1 prj.read(f"{datapath}/france_parts.qgs",readflags)

195 ms ± 44 ms per loop (mean ± std. dev. of 7 runs, 1 loop each)

There is a factor x10 between Qgis 3.24 et Qgis 3.26 for the exact same 
project.
This has serious impact on requests: landing page catalog request time 
increased from approximatevely 110ms to more than 3.0s with our test 
data set.


David Marteau
www.3liz.com <http://www.3liz.com>
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