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Make concave hull alg more efficient

- remove temporary layers from context, delete them as soon as they
are finished with
- directly remove features via data provider, instead of selecting
and using edit buffer
- use native geometry methods for splitting to single features
and removing rings
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nyalldawson committed Jul 6, 2017
1 parent 70cc196 commit a2af3a9345dcd872a897ef632c277394e9f95f95
Showing with 13 additions and 16 deletions.
  1. +13 −16 python/plugins/processing/algs/qgis/
@@ -88,7 +88,7 @@ def processAlgorithm(self, parameters, context, feedback):
# Delaunay triangulation from input point layer
feedback.setProgressText('Creating Delaunay triangles...'))
delone_triangles ="qgis:delaunaytriangulation", {'INPUT': parameters[ConcaveHull.INPUT], 'OUTPUT': 'memory:'}, feedback=feedback, context=context)['OUTPUT']
delaunay_layer = QgsProcessingUtils.mapLayerFromString(delone_triangles, context)
delaunay_layer = context.takeResultLayer(delone_triangles)

# Get max edge length from Delaunay triangles
feedback.setProgressText('Computing edges max length...'))
@@ -127,48 +127,45 @@ def processAlgorithm(self, parameters, context, feedback):
i += 1

# Remove features

# Dissolve all Delaunay triangles
feedback.setProgressText('Dissolving Delaunay triangles...'))
dissolved ="native:dissolve", {'INPUT':, 'OUTPUT': 'memory:'}, feedback=feedback, context=context)['OUTPUT']
dissolved_layer = QgsProcessingUtils.mapLayerFromString(dissolved, context)
dissolved ="native:dissolve", {'INPUT': delaunay_layer, 'OUTPUT': 'memory:'}, feedback=feedback, context=context)['OUTPUT']
dissolved_layer = context.takeResultLayer(dissolved)

# Save result
feedback.setProgressText('Saving data...'))
feat = QgsFeature()

# Not needed anymore, free up some resources
del delaunay_layer
del dissolved_layer

(sink, dest_id) = self.parameterAsSink(parameters, self.OUTPUT, context,
layer.fields(), QgsWkbTypes.Polygon, layer.sourceCrs())

geom = feat.geometry()
if no_multigeom and geom.isMultipart():
# Only singlepart geometries are allowed
geom_list = geom.asMultiPolygon()
for single_geom_list in geom_list:
geom_list = geom.asGeometryCollection()
for single_geom in geom_list:
if feedback.isCanceled():

single_feature = QgsFeature()
single_geom = QgsGeometry.fromPolygon(single_geom_list)
if not holes:
# Delete holes
deleted = True
while deleted:
deleted = single_geom.deleteRing(1)
single_geom = single_geom.removeInteriorRings()
sink.addFeature(single_feature, QgsFeatureSink.FastInsert)
# Multipart geometries are allowed
if not holes:
# Delete holes
deleted = True
while deleted:
deleted = geom.deleteRing(1)
geom = geom.removeInteriorRings()
sink.addFeature(feat, QgsFeatureSink.FastInsert)

return {self.OUTPUT: dest_id}

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