Howdy!
I have a local layer with a few polygon features and a remote PostGIS
layer with millions of polygon features.
When I run native:intersection with the small local layer as input and
the big remote layer as overlay, QGIS will fetch all features from the
big remote layer and create a local spatial index. This uses lots of
bandwidth and takes a long time.
I would have expected QGIS to handle PostGIS layers in a way that their
existing indexes are utilised.
Searching for the processing log message "Creating spatial index", it
seems like
https://github.com/qgis/QGIS/blob/d238f1132bbbf8c479356b9267cff7ee137e5be9/src/analysis/processing/qgsoverlayutils.cpp#L233
is responsible for that. If I read the code correctly, a QgsSpatialIndex
will *always* be created for the overlay layer.
Is there a way to do intersections where existing (PostGIS) indexes are
used?
Cheers, Hannes
PS: A workaround solution could be using some custom Python code around
qgis:postgisexecuteandloadsql I guess.
--
Johannes Kröger / GIS-Entwickler/-Berater
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