Add expression based filter for QgsVectorLayerExporter

python/PyQt6/core/auto_generated/vector/qgsvectorlayerexporter.sip.in

@@ -70,6 +70,10 @@ Encapsulates options for use with QgsVectorLayerExporter.
 %Docstring
 Sets whether the export should only include selected features.
 
+.. warning::
+
+   This setting is incompatible with :py:func:`~ExportOptions.setFilterExpression`
+
 .. note::
 
    This option only applies when the :py:func:`QgsVectorLayerExporter.exportLayer()` method is used.
@@ -81,6 +85,10 @@ Sets whether the export should only include selected features.
 %Docstring
 Returns whether the export will only include selected features.
 
+.. warning::
+
+   This setting is incompatible with :py:func:`~ExportOptions.filterExpression`
+
 .. note::
 
    This option only applies when the :py:func:`QgsVectorLayerExporter.exportLayer()` method is used.
@@ -140,6 +148,58 @@ Only features with a bounding box intersecting this extent will be exported.
    This option only applies when the :py:func:`QgsVectorLayerExporter.exportLayer()` method is used.
 
 .. seealso:: :py:func:`setExtent`
+%End
+
+        void setFilterExpression( const QString &expression );
+%Docstring
+Set the filter ``expression`` for the features to export.
+
+Only features matching this expression will be exported.
+
+.. warning::
+
+   This setting is incompatible with :py:func:`~ExportOptions.setSelectedOnly`
+
+.. note::
+
+   This option only applies when the :py:func:`QgsVectorLayerExporter.exportLayer()` method is used.
+
+.. seealso:: :py:func:`setExpressionContext`
+
+.. seealso:: :py:func:`filterExpression`
+%End
+
+        QString filterExpression() const;
+%Docstring
+Returns the filter expression for features to export.
+
+Only features matching this expression will be exported.
+
+.. warning::
+
+   This setting is incompatible with :py:func:`~ExportOptions.selectedOnly`
+
+.. note::
+
+   This option only applies when the :py:func:`QgsVectorLayerExporter.exportLayer()` method is used.
+
+.. seealso:: :py:func:`expressionContext`
+
+.. seealso:: :py:func:`setFilterExpression`
+%End
+
+        void setExpressionContext( const QgsExpressionContext &context );
+%Docstring
+Sets the expression ``context`` to use when a :py:func:`~ExportOptions.filterExpression` is set.
+
+.. seealso:: :py:func:`expressionContext`
+%End
+
+        const QgsExpressionContext &expressionContext() const;
+%Docstring
+Returns the expression context used when a :py:func:`~ExportOptions.filterExpression` is set.
+
+.. seealso:: :py:func:`setExpressionContext`
 %End
 
     };

python/core/auto_generated/vector/qgsvectorlayerexporter.sip.in

@@ -70,6 +70,10 @@ Encapsulates options for use with QgsVectorLayerExporter.
 %Docstring
 Sets whether the export should only include selected features.
 
+.. warning::
+
+   This setting is incompatible with :py:func:`~ExportOptions.setFilterExpression`
+
 .. note::
 
    This option only applies when the :py:func:`QgsVectorLayerExporter.exportLayer()` method is used.
@@ -81,6 +85,10 @@ Sets whether the export should only include selected features.
 %Docstring
 Returns whether the export will only include selected features.
 
+.. warning::
+
+   This setting is incompatible with :py:func:`~ExportOptions.filterExpression`
+
 .. note::
 
    This option only applies when the :py:func:`QgsVectorLayerExporter.exportLayer()` method is used.
@@ -140,6 +148,58 @@ Only features with a bounding box intersecting this extent will be exported.
    This option only applies when the :py:func:`QgsVectorLayerExporter.exportLayer()` method is used.
 
 .. seealso:: :py:func:`setExtent`
+%End
+
+        void setFilterExpression( const QString &expression );
+%Docstring
+Set the filter ``expression`` for the features to export.
+
+Only features matching this expression will be exported.
+
+.. warning::
+
+   This setting is incompatible with :py:func:`~ExportOptions.setSelectedOnly`
+
+.. note::
+
+   This option only applies when the :py:func:`QgsVectorLayerExporter.exportLayer()` method is used.
+
+.. seealso:: :py:func:`setExpressionContext`
+
+.. seealso:: :py:func:`filterExpression`
+%End
+
+        QString filterExpression() const;
+%Docstring
+Returns the filter expression for features to export.
+
+Only features matching this expression will be exported.
+
+.. warning::
+
+   This setting is incompatible with :py:func:`~ExportOptions.selectedOnly`
+
+.. note::
+
+   This option only applies when the :py:func:`QgsVectorLayerExporter.exportLayer()` method is used.
+
+.. seealso:: :py:func:`expressionContext`
+
+.. seealso:: :py:func:`setFilterExpression`
+%End
+
+        void setExpressionContext( const QgsExpressionContext &context );
+%Docstring
+Sets the expression ``context`` to use when a :py:func:`~ExportOptions.filterExpression` is set.
+
+.. seealso:: :py:func:`expressionContext`
+%End
+
+        const QgsExpressionContext &expressionContext() const;
+%Docstring
+Returns the expression context used when a :py:func:`~ExportOptions.filterExpression` is set.
+
+.. seealso:: :py:func:`setExpressionContext`
 %End
 
     };

src/core/vector/qgsvectorlayerexporter.cpp

@@ -81,6 +81,26 @@ QgsReferencedRectangle QgsVectorLayerExporter::ExportOptions::extent() const
   return mExtent;
 }
 
+void QgsVectorLayerExporter::ExportOptions::setFilterExpression( const QString &expression )
+{
+  mFilterExpression = expression;
+}
+
+QString QgsVectorLayerExporter::ExportOptions::filterExpression() const
+{
+  return mFilterExpression;
+}
+
+void QgsVectorLayerExporter::ExportOptions::setExpressionContext( const QgsExpressionContext &context )
+{
+  mExpressionContext = context;
+}
+
+const QgsExpressionContext &QgsVectorLayerExporter::ExportOptions::expressionContext() const
+{
+  return mExpressionContext;
+}
+
 
 //
 // QgsVectorLayerExporter
@@ -423,7 +443,12 @@ Qgis::VectorExportResult QgsVectorLayerExporter::exportLayer( QgsVectorLayer *la
     }
   }
 
-  if ( exportOptions.selectedOnly() )
+  if ( !exportOptions.filterExpression().isEmpty() )
+  {
+    req.setFilterExpression( exportOptions.filterExpression() );
+    req.setExpressionContext( exportOptions.expressionContext() );
+  }
+  else if ( exportOptions.selectedOnly() )
   {
     req.setFilterFids( layer->selectedFeatureIds() );
   }

src/core/vector/qgsvectorlayerexporter.h

@@ -86,6 +86,8 @@ class CORE_EXPORT QgsVectorLayerExporter : public QgsFeatureSink
         /**
          * Sets whether the export should only include selected features.
          *
+         * \warning This setting is incompatible with setFilterExpression()
+         *
          * \note This option only applies when the QgsVectorLayerExporter::exportLayer() method is used.
          *
          * \seee selectedOnly()
@@ -95,6 +97,8 @@ class CORE_EXPORT QgsVectorLayerExporter : public QgsFeatureSink
         /**
          * Returns whether the export will only include selected features.
          *
+         * \warning This setting is incompatible with filterExpression()
+         *
          * \note This option only applies when the QgsVectorLayerExporter::exportLayer() method is used.
          *
          * \seee setSelectedOnly()
@@ -151,6 +155,48 @@ class CORE_EXPORT QgsVectorLayerExporter : public QgsFeatureSink
          */
         QgsReferencedRectangle extent() const;
 
+        /**
+         * Set the filter \a expression for the features to export.
+         *
+         * Only features matching this expression will be exported.
+         *
+         * \warning This setting is incompatible with setSelectedOnly()
+         *
+         * \note This option only applies when the QgsVectorLayerExporter::exportLayer() method is used.
+         *
+         * \see setExpressionContext()
+         * \see filterExpression()
+         */
+        void setFilterExpression( const QString &expression );
+
+        /**
+         * Returns the filter expression for features to export.
+         *
+         * Only features matching this expression will be exported.
+         *
+         * \warning This setting is incompatible with selectedOnly()
+         *
+         * \note This option only applies when the QgsVectorLayerExporter::exportLayer() method is used.
+         *
+         * \see expressionContext()
+         * \see setFilterExpression()
+         */
+        QString filterExpression() const;
+
+        /**
+         * Sets the expression \a context to use when a filterExpression() is set.
+         *
+         * \see expressionContext()
+         */
+        void setExpressionContext( const QgsExpressionContext &context );
+
+        /**
+         * Returns the expression context used when a filterExpression() is set.
+         *
+         * \see setExpressionContext()
+         */
+        const QgsExpressionContext &expressionContext() const;
+
       private:
 
         bool mSelectedOnly = false;
@@ -161,6 +207,9 @@ class CORE_EXPORT QgsVectorLayerExporter : public QgsFeatureSink
 
         QgsReferencedRectangle mExtent;
 
+        QString mFilterExpression;
+        QgsExpressionContext mExpressionContext;
+
     };
 
     /**

tests/src/python/test_qgsvectorlayerexporter.py

@@ -196,6 +196,59 @@ class TestQgsVectorLayerExporter(QgisTestCase):
                 [f["fldtxt"] for f in layer.getFeatures()], ["test2", "test3"]
             )
 
+    def test_expression_filter(self):
+        with tempfile.TemporaryDirectory() as temp_dir:
+            dest_file_name = Path(temp_dir) / "test_expression.gpkg"
+
+            # create a layer to export
+            layer = QgsVectorLayer(
+                "Point?field=fldtxt:string&field=fldint:integer", "addfeat", "memory"
+            )
+            self.assertTrue(layer.isValid())
+            pr = layer.dataProvider()
+            f = QgsFeature()
+            f.setAttributes(["test", 123])
+            f.setGeometry(QgsGeometry.fromPointXY(QgsPointXY(1, 2)))
+            f2 = QgsFeature()
+            f2.setAttributes(["abc", 457])
+            f2.setGeometry(QgsGeometry.fromPointXY(QgsPointXY(3, 4)))
+            f3 = QgsFeature()
+            f3.setAttributes(["def", 4573])
+            f3.setGeometry(QgsGeometry.fromPointXY(QgsPointXY(5, 6)))
+            f4 = QgsFeature()
+            f4.setAttributes(["a feature", 4574])
+            f4.setGeometry(QgsGeometry.fromPointXY(QgsPointXY(7, 8)))
+            self.assertTrue(pr.addFeature(f))
+            self.assertTrue(pr.addFeature(f2))
+            self.assertTrue(pr.addFeature(f3))
+            self.assertTrue(pr.addFeature(f4))
+            layer.setCrs(QgsCoordinateReferenceSystem("EPSG:4326"))
+
+            export_options = QgsVectorLayerExporter.ExportOptions()
+            export_options.setFilterExpression("left(\"fldtxt\", 1) = 'a'")
+
+            res, error = QgsVectorLayerExporter.exportLayer(
+                layer,
+                dest_file_name.as_posix(),
+                "ogr",
+                export_options,
+                providerOptions={"layerName": "expression", "update": True},
+            )
+            self.assertEqual(res, Qgis.VectorExportResult.Success)
+
+            # true to read result
+            layer = QgsVectorLayer(
+                dest_file_name.as_posix() + "|layername=expression",
+                "test",
+                "ogr",
+            )
+            self.assertTrue(layer.isValid())
+            self.assertEqual(layer.featureCount(), 2)
+
+            self.assertCountEqual(
+                [f["fldtxt"] for f in layer.getFeatures()], ["abc", "a feature"]
+            )
+
     @unittest.skipIf(
         int(gdal.VersionInfo("VERSION_NUM")) < GDAL_COMPUTE_VERSION(3, 8, 0),
         "GDAL 3.8 required",