[processing] Optimise uniqueValues method

Now it uses the standard QgsVectorLayer.uniqueValues() method where possible so that provider side optimisations are used Also add test, and optimise request when using selected features only
qgis · Oct 12, 2016 · 6605a22 · 6605a22
1 parent 05ea4be
commit 6605a22
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Showing 2 changed files with 42 additions and 6 deletions.
diff --git a/python/plugins/processing/tests/ToolsTest.py b/python/plugins/processing/tests/ToolsTest.py
@@ -122,6 +122,32 @@ def testValues(self):
 
         ProcessingConfig.setSettingValue(ProcessingConfig.USE_SELECTED, previous_value)
 
+    def testUniqueValues(self):
+        ProcessingConfig.initialize()
+
+        test_data = points2()
+        test_layer = QgsVectorLayer(test_data, 'test', 'ogr')
+
+        # field by index
+        v = vector.uniqueValues(test_layer, 3)
+        self.assertEqual(len(v), len(set(v)))
+        self.assertEqual(set(v), set([2, 1, 0]))
+
+        # field by name
+        v = vector.uniqueValues(test_layer, 'id_2')
+        self.assertEqual(len(v), len(set(v)))
+        self.assertEqual(set(v), set([2, 1, 0]))
+
+        # test with selected features
+        previous_value = ProcessingConfig.getSetting(ProcessingConfig.USE_SELECTED)
+        ProcessingConfig.setSettingValue(ProcessingConfig.USE_SELECTED, True)
+        test_layer.selectByIds([2, 4, 6])
+        v = vector.uniqueValues(test_layer, 'id')
+        self.assertEqual(len(v), len(set(v)))
+        self.assertEqual(set(v), set([5, 7, 3]))
+
+        ProcessingConfig.setSettingValue(ProcessingConfig.USE_SELECTED, previous_value)
+
 
 if __name__ == '__main__':
     unittest.main()
diff --git a/python/plugins/processing/tools/vector.py b/python/plugins/processing/tools/vector.py
@@ -122,13 +122,23 @@ def uniqueValues(layer, attribute):
     Attribute can be defined using a field names or a zero-based
     field index. It considers the existing selection.
     """
-    values = []
+
     fieldIndex = resolveFieldIndex(layer, attribute)
-    feats = features(layer)
-    for feat in feats:
-        if feat.attributes()[fieldIndex] not in values:
-            values.append(feat.attributes()[fieldIndex])
-    return values
+    if ProcessingConfig.getSetting(ProcessingConfig.USE_SELECTED) \
+            and layer.selectedFeatureCount() > 0:
+
+        # iterate through selected features
+        values = []
+        request = QgsFeatureRequest().setSubsetOfAttributes([fieldIndex]).setFlags(QgsFeatureRequest.NoGeometry)
+        feats = features(layer, request)
+        for feat in feats:
+            if feat.attributes()[fieldIndex] not in values:
+                values.append(feat.attributes()[fieldIndex])
+        return values
+    else:
+        # no selection, or not considering selecting
+        # so we can take advantage of provider side unique value optimisations
+        return layer.uniqueValues(fieldIndex)
 
 
 def resolveFieldIndex(layer, attr):