On 11/24/2013 04:17 PM, Richard Duivenvoorde wrote:
On 24-11-13 21:30, Lee Hachadoorian wrote:
I was using `Vector → Analysis Tools → Points in polygon` to count
events in a hexgrid (created with MMQGIS). The point data came from a
PostGIS layer. The layer has a query restriction and the filtered data
set has ~230k points. When I run it, it just crashes (sometimes
immediately, sometimes after several seconds). When I export the PostGIS
layer to shapefile and run it, it works (although it takes ~2 hours to
run).
Are there issues with using this feature with PostGIS layers? Is it the
size of the dataset?
Hi Lee,
I did some some testing here, with a (small) postgis dataset. No
problems here.
The vector analysis tools are written in Python, and I think it has been
asked before to redo at least some of them in cpp to make these faster.
Especially those that are often used with larger datasets...
(Google Summer of Code project?)
I think in these cases the best way to test this is:
- try it with the latest/testing version on different computers
(preferably different OS's too)
- if still a problem: create an issue, AND provide the test data
somewhere (so others can test and confirm this issue)
- depending on your tools: maybe run qgis via strace and append the
output to the issue
As you can see here:
https://github.com/qgis/QGIS/blob/master/python/plugins/fTools/tools/doPointsInPolygon.py#L180
the plugin apparently creates an index with (in your case) all 230K
points in it.
Later, the features are fetched one by one to test if they intersect
(#206). I would think that could be done easier/faster(??) nowadays by
using the inGeom.boundingBox
Well as said: plz create an issue and provide some test data, maybe
other people interested in this can try things out this too...
Regards,
Richard Duivenvoorde
Tested with a random sample from my original data, only 7k records, and
it ran to completion. Will create an issue to document it.
BTW, because it wasn't working in QGIS I imported my hexgrid into
PostGIS and ran the analysis in-database using
`ST_Contains(hex_layer.geom, point_layer.geom) ... GROUP BY
hex_layer.gid`, and the query ran in 2 seconds (literally).
Best,
--Lee
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