Push minimumValues/maximumValues up to QgsFeatureSource base class

Allows these methods to be called on feature sources

python/core/processing/qgsprocessingutils.sip

@@ -232,6 +232,12 @@ class QgsProcessingFeatureSource : QgsFeatureSource
 
     virtual QString sourceName() const;
 
+    virtual QSet<QVariant> uniqueValues( int fieldIndex, int limit = -1 ) const;
+
+    virtual QVariant minimumValue( int fieldIndex ) const;
+
+    virtual QVariant maximumValue( int fieldIndex ) const;
+
 
 };
 

python/core/qgsfeaturesource.sip

@@ -81,9 +81,31 @@ class QgsFeatureSource
  If specified, the ``limit`` option can be used to limit the number of returned values.
  The base class implementation uses a non-optimised approach of looping through
  all features in the source.
+.. seealso:: minimumValue()
+.. seealso:: maximumValue()
  :rtype: set of QVariant
 %End
 
+    virtual QVariant minimumValue( int fieldIndex ) const;
+%Docstring
+ Returns the minimum value for an attribute column or an invalid variant in case of error.
+ The base class implementation uses a non-optimised approach of looping through
+ all features in the source.
+.. seealso:: maximumValue()
+.. seealso:: uniqueValues()
+ :rtype: QVariant
+%End
+
+    virtual QVariant maximumValue( int fieldIndex ) const;
+%Docstring
+ Returns the maximum value for an attribute column or an invalid variant in case of error.
+ The base class implementation uses a non-optimised approach of looping through
+ all features in the source.
+.. seealso:: minimumValue()
+.. seealso:: uniqueValues()
+ :rtype: QVariant
+%End
+
     virtual QgsRectangle sourceExtent() const;
 %Docstring
  Returns the extent of all geometries from the source.

python/core/qgsvectorlayer.sip

@@ -1537,7 +1537,8 @@ Assembles mUpdatedFields considering provider fields, joined fields and added fi
  :rtype: list of str
 %End
 
-    QVariant minimumValue( int index ) const;
+    virtual QVariant minimumValue( int index ) const;
+
 %Docstring
  Returns the minimum value for an attribute column or an invalid variant in case of error.
  Note that in some circumstances when unsaved changes are present for the layer then the
@@ -1548,7 +1549,8 @@ Assembles mUpdatedFields considering provider fields, joined fields and added fi
  :rtype: QVariant
 %End
 
-    QVariant maximumValue( int index ) const;
+    virtual QVariant maximumValue( int index ) const;
+
 %Docstring
  Returns the maximum value for an attribute column or an invalid variant in case of error.
  Note that in some circumstances when unsaved changes are present for the layer then the

src/core/processing/qgsprocessingutils.cpp

@@ -566,3 +566,18 @@ QString QgsProcessingFeatureSource::sourceName() const
   return mSource->sourceName();
 
 }
+
+QSet<QVariant> QgsProcessingFeatureSource::uniqueValues( int fieldIndex, int limit ) const
+{
+  return mSource->uniqueValues( fieldIndex, limit );
+}
+
+QVariant QgsProcessingFeatureSource::minimumValue( int fieldIndex ) const
+{
+  return mSource->minimumValue( fieldIndex );
+}
+
+QVariant QgsProcessingFeatureSource::maximumValue( int fieldIndex ) const
+{
+  return mSource->maximumValue( fieldIndex );
+}

src/core/processing/qgsprocessingutils.h

@@ -282,6 +282,9 @@ class CORE_EXPORT QgsProcessingFeatureSource : public QgsFeatureSource
     QgsWkbTypes::Type wkbType() const override;
     long featureCount() const override;
     QString sourceName() const override;
+    QSet<QVariant> uniqueValues( int fieldIndex, int limit = -1 ) const override;
+    QVariant minimumValue( int fieldIndex ) const override;
+    QVariant maximumValue( int fieldIndex ) const override;
 
   private:
 

src/core/qgsfeaturesource.cpp

@@ -40,6 +40,52 @@ QSet<QVariant> QgsFeatureSource::uniqueValues( int fieldIndex, int limit ) const
   return values;
 }
 
+QVariant QgsFeatureSource::minimumValue( int fieldIndex ) const
+{
+  if ( fieldIndex < 0 || fieldIndex >= fields().count() )
+    return QVariant();
+
+  QgsFeatureRequest req;
+  req.setFlags( QgsFeatureRequest::NoGeometry );
+  req.setSubsetOfAttributes( QgsAttributeList() << fieldIndex );
+
+  QVariant min;
+  QgsFeatureIterator it = getFeatures( req );
+  QgsFeature f;
+  while ( it.nextFeature( f ) )
+  {
+    QVariant v = f.attribute( fieldIndex );
+    if ( v.isValid() && qgsVariantLessThan( v, min ) )
+    {
+      min = v;
+    }
+  }
+  return min;
+}
+
+QVariant QgsFeatureSource::maximumValue( int fieldIndex ) const
+{
+  if ( fieldIndex < 0 || fieldIndex >= fields().count() )
+    return QVariant();
+
+  QgsFeatureRequest req;
+  req.setFlags( QgsFeatureRequest::NoGeometry );
+  req.setSubsetOfAttributes( QgsAttributeList() << fieldIndex );
+
+  QVariant max;
+  QgsFeatureIterator it = getFeatures( req );
+  QgsFeature f;
+  while ( it.nextFeature( f ) )
+  {
+    QVariant v = f.attribute( fieldIndex );
+    if ( v.isValid() && qgsVariantGreaterThan( v, max ) )
+    {
+      max = v;
+    }
+  }
+  return max;
+}
+
 QgsRectangle QgsFeatureSource::sourceExtent() const
 {
   QgsRectangle r;

src/core/qgsfeaturesource.h

@@ -89,9 +89,27 @@ class CORE_EXPORT QgsFeatureSource
      * If specified, the \a limit option can be used to limit the number of returned values.
      * The base class implementation uses a non-optimised approach of looping through
      * all features in the source.
+     * \see minimumValue()
+     * \see maximumValue()
      */
     virtual QSet<QVariant> uniqueValues( int fieldIndex, int limit = -1 ) const;
 
+    /** Returns the minimum value for an attribute column or an invalid variant in case of error.
+     * The base class implementation uses a non-optimised approach of looping through
+     * all features in the source.
+     * \see maximumValue()
+     * \see uniqueValues()
+     */
+    virtual QVariant minimumValue( int fieldIndex ) const;
+
+    /** Returns the maximum value for an attribute column or an invalid variant in case of error.
+     * The base class implementation uses a non-optimised approach of looping through
+     * all features in the source.
+     * \see minimumValue()
+     * \see uniqueValues()
+     */
+    virtual QVariant maximumValue( int fieldIndex ) const;
+
     /**
      * Returns the extent of all geometries from the source.
      * The base class implementation uses a non-optimised approach of looping through

src/core/qgsvectordataprovider.h

@@ -177,7 +177,7 @@ class CORE_EXPORT QgsVectorDataProvider : public QgsDataProvider, public QgsFeat
      * and maximal values. If provider has facilities to retrieve minimal
      * value directly, override this function.
      */
-    virtual QVariant minimumValue( int index ) const;
+    virtual QVariant minimumValue( int index ) const override;
 
     /**
      * Returns the maximum value of an attribute
@@ -187,7 +187,7 @@ class CORE_EXPORT QgsVectorDataProvider : public QgsDataProvider, public QgsFeat
      * and maximal values. If provider has facilities to retrieve maximal
      * value directly, override this function.
      */
-    virtual QVariant maximumValue( int index ) const;
+    virtual QVariant maximumValue( int index ) const override;
 
     /**
      * Returns unique string values of an attribute which contain a specified subset string. Subset

src/core/qgsvectorlayer.h

@@ -1452,7 +1452,7 @@ class CORE_EXPORT QgsVectorLayer : public QgsMapLayer, public QgsExpressionConte
      * \see maximumValue()
      * \see uniqueValues()
      */
-    QVariant minimumValue( int index ) const;
+    QVariant minimumValue( int index ) const override;
 
     /** Returns the maximum value for an attribute column or an invalid variant in case of error.
      * Note that in some circumstances when unsaved changes are present for the layer then the
@@ -1461,7 +1461,7 @@ class CORE_EXPORT QgsVectorLayer : public QgsMapLayer, public QgsExpressionConte
      * \see minimumValue()
      * \see uniqueValues()
      */
-    QVariant maximumValue( int index ) const;
+    QVariant maximumValue( int index ) const override;
 
     /** Calculates an aggregated value from the layer's features.
      * \param aggregate aggregate to calculate

tests/src/python/featuresourcetestbase.py

@@ -635,3 +635,15 @@ class FeatureSourceTestCase(object):
 
             assert f.hasGeometry(), 'Expected geometry, got none'
             self.assertTrue(f.isValid())
+
+    def testUniqueValues(self):
+        self.assertEqual(set(self.source.uniqueValues(1)), set([-200, 100, 200, 300, 400]))
+        assert set(['Apple', 'Honey', 'Orange', 'Pear', NULL]) == set(self.source.uniqueValues(2)), 'Got {}'.format(set(self.source.uniqueValues(2)))
+
+    def testMinimumValue(self):
+        self.assertEqual(self.source.minimumValue(1), -200)
+        self.assertEqual(self.source.minimumValue(2), 'Apple')
+
+    def testMaximumValue(self):
+        self.assertEqual(self.source.maximumValue(1), 400)
+        self.assertEqual(self.source.maximumValue(2), 'Pear')

tests/src/python/test_qgsfeaturesource.py

@@ -62,6 +62,30 @@ class TestQgsFeatureSource(unittest.TestCase):
         self.assertEqual(layer.dataProvider().uniqueValues(0), {'test', 'test2', 'test3', 'test4'})
         self.assertEqual(layer.dataProvider().uniqueValues(1), {1, 3, 3, 4})
 
+    def testMinValues(self):
+        """
+        Test retrieving min values using base class method
+        """
+
+        # memory provider uses base class method
+        layer = createLayerWithFivePoints()
+        self.assertFalse(layer.dataProvider().minimumValue(-1))
+        self.assertFalse(layer.dataProvider().minimumValue(100))
+        self.assertEqual(layer.dataProvider().minimumValue(0), 'test')
+        self.assertEqual(layer.dataProvider().minimumValue(1), 1)
+
+    def testMaxValues(self):
+        """
+        Test retrieving min values using base class method
+        """
+
+        # memory provider uses base class method
+        layer = createLayerWithFivePoints()
+        self.assertFalse(layer.dataProvider().maximumValue(-1))
+        self.assertFalse(layer.dataProvider().maximumValue(100))
+        self.assertEqual(layer.dataProvider().maximumValue(0), 'test4')
+        self.assertEqual(layer.dataProvider().maximumValue(1), 4)
+
 
 if __name__ == '__main__':
     unittest.main()

tests/src/python/test_qgsvectorlayer.py

@@ -2511,6 +2511,12 @@ class TestQgsVectorLayerSourceAddedFeaturesInBuffer(unittest.TestCase, FeatureSo
         """
         pass
 
+    def testMinimumValue(self):
+        """ Skip min values test - due to inconsistencies in how null values are treated by providers.
+        They are included here, but providers don't include them.... which is right?
+        """
+        pass
+
 
 class TestQgsVectorLayerSourceChangedGeometriesInBuffer(unittest.TestCase, FeatureSourceTestCase):
 
@@ -2661,6 +2667,21 @@ class TestQgsVectorLayerSourceChangedAttributesInBuffer(unittest.TestCase, Featu
         """
         pass
 
+    def testUniqueValues(self):
+        """ Skip unique values test - as noted in the docs this is unreliable when features are in the buffer
+        """
+        pass
+
+    def testMinimumValue(self):
+        """ Skip min values test - as noted in the docs this is unreliable when features are in the buffer
+        """
+        pass
+
+    def testMaximumValue(self):
+        """ Skip max values test - as noted in the docs this is unreliable when features are in the buffer
+        """
+        pass
+
 
 class TestQgsVectorLayerSourceDeletedFeaturesInBuffer(unittest.TestCase, FeatureSourceTestCase):
 
@@ -2746,6 +2767,21 @@ class TestQgsVectorLayerSourceDeletedFeaturesInBuffer(unittest.TestCase, Feature
         """
         pass
 
+    def testUniqueValues(self):
+        """ Skip unique values test - as noted in the docs this is unreliable when features are in the buffer
+        """
+        pass
+
+    def testMinimumValue(self):
+        """ Skip min values test - as noted in the docs this is unreliable when features are in the buffer
+        """
+        pass
+
+    def testMaximumValue(self):
+        """ Skip max values test - as noted in the docs this is unreliable when features are in the buffer
+        """
+        pass
+
 # TODO:
 # - fetch rect: feat with changed geometry: 1. in rect, 2. out of rect
 # - more join tests

tests/src/python/test_qgsvectorlayercache.py

@@ -90,6 +90,21 @@ class TestQgsVectorLayerCache(unittest.TestCase, FeatureSourceTestCase):
         """
         pass
 
+    def testUniqueValues(self):
+        """ Skip unique values test - not implemented by the cache (yet)
+        """
+        pass
+
+    def testMinimumValue(self):
+        """ Skip min values test - not implemented by the cache (yet)
+        """
+        pass
+
+    def testMaximumValue(self):
+        """ Skip max values test - not implemented by the cache (yet)
+        """
+        pass
+
 
 if __name__ == '__main__':
     unittest.main()