Add QgsDataProvider::ReadFlag::SkipFeatureCount and implement it in O…

…GR provider to avoid featureCount() to be called
qgis · Nov 12, 2020 · 3260807 · 3260807
1 parent c8510b1
commit 3260807
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Showing 4 changed files with 28 additions and 1 deletion.
diff --git a/python/core/auto_generated/qgsdataprovider.sip.in b/python/core/auto_generated/qgsdataprovider.sip.in
@@ -73,6 +73,7 @@ Abstract base class for spatial data provider implementations.
     enum ReadFlag
     {
       FlagTrustDataSource,
+      SkipFeatureCount,
     };
     typedef QFlags<QgsDataProvider::ReadFlag> ReadFlags;
 

diff --git a/src/core/providers/ogr/qgsogrprovider.cpp b/src/core/providers/ogr/qgsogrprovider.cpp
@@ -953,7 +953,8 @@ void QgsOgrProvider::addSubLayerDetailsToSubLayerList( int i, QgsOgrLayer *layer
 
 QStringList QgsOgrProvider::subLayers() const
 {
-  return _subLayers( true );
+  const bool withFeatureCount = ( mReadFlags & QgsDataProvider::SkipFeatureCount ) == 0;
+  return _subLayers( withFeatureCount );
 }
 
 QgsLayerMetadata QgsOgrProvider::layerMetadata() const
@@ -1604,6 +1605,10 @@ QgsWkbTypes::Type QgsOgrProvider::wkbType() const
  */
 long QgsOgrProvider::featureCount() const
 {
+  if ( ( mReadFlags & QgsDataProvider::SkipFeatureCount ) != 0 )
+  {
+    return QgsVectorDataProvider::UnknownCount;
+  }
   if ( mRefreshFeatureCount )
   {
     mRefreshFeatureCount = false;

diff --git a/src/core/qgsdataprovider.h b/src/core/qgsdataprovider.h
@@ -122,6 +122,7 @@ class CORE_EXPORT QgsDataProvider : public QObject
     enum ReadFlag
     {
       FlagTrustDataSource = 1 << 0, //!< Trust datasource config (primary key unicity, geometry type and srid, etc). Improves provider load time by skipping expensive checks like primary key unicity, geometry type and srid and by using estimated metadata on data load. Since QGIS 3.16
+      SkipFeatureCount = 1 << 1, //!< Make featureCount() return -1 to indicate unknown, and subLayers() to return a unknown feature count as well. Since QGIS 3.18. Only implemented by OGR provider at time of writing.
     };
     Q_DECLARE_FLAGS( ReadFlags, ReadFlag )
 

diff --git a/tests/src/python/test_provider_shapefile.py b/tests/src/python/test_provider_shapefile.py
@@ -22,12 +22,14 @@
 from osgeo import gdal
 from qgis.core import (
     QgsApplication,
+    QgsDataProvider,
     QgsSettings,
     QgsFeature,
     QgsField,
     QgsGeometry,
     QgsVectorLayer,
     QgsFeatureRequest,
+    QgsProviderRegistry,
     QgsVectorDataProvider,
     QgsWkbTypes,
     QgsVectorLayerExporter,
@@ -1076,6 +1078,24 @@ def testEncoding(self):
         self.assertTrue(vl.isValid())
         self.assertEqual([f.attributes() for f in vl.dataProvider().getFeatures()], [['abcŐ'], ['abcŐabcŐabcŐ']])
 
+    def testSkipFeatureCountOnFeatureCount(self):
+        """Test QgsDataProvider.SkipFeatureCount on featureCount()"""
+
+        testPath = TEST_DATA_DIR + '/' + 'lines.shp'
+        provider = QgsProviderRegistry.instance().createProvider('ogr', testPath, QgsDataProvider.ProviderOptions(), QgsDataProvider.SkipFeatureCount)
+        self.assertTrue(provider.isValid())
+        self.assertEqual(provider.featureCount(), QgsVectorDataProvider.UnknownCount)
+
+    def testSkipFeatureCountOnSubLayers(self):
+        """Test QgsDataProvider.SkipFeatureCount on subLayers()"""
+
+        datasource = os.path.join(TEST_DATA_DIR, 'shapefile')
+        provider = QgsProviderRegistry.instance().createProvider('ogr', datasource, QgsDataProvider.ProviderOptions(), QgsDataProvider.SkipFeatureCount)
+        self.assertTrue(provider.isValid())
+        sublayers = provider.subLayers()
+        self.assertTrue(len(sublayers) > 1)
+        self.assertEqual(sublayers[0].split(QgsDataProvider.sublayerSeparator())[2], '-1')
+
 
 if __name__ == '__main__':
     unittest.main()