Merge pull request #3278 from mhugo/master

Fix virtual layer construction from joined layer

Author: Hugo Mercier

src/core/qgsvirtuallayerdefinitionutils.cpp

@@ -17,6 +17,7 @@ email                : hugo dot mercier at oslandia dot com
 #include "qgsvirtuallayerdefinitionutils.h"
 #include "qgsvectorlayer.h"
 #include "qgsvectordataprovider.h"
+#include "qgsmaplayerregistry.h"
 
 QgsVirtualLayerDefinition QgsVirtualLayerDefinitionUtils::fromJoinedLayer( QgsVectorLayer* layer )
 {
@@ -25,8 +26,6 @@ QgsVirtualLayerDefinition QgsVirtualLayerDefinitionUtils::fromJoinedLayer( QgsVe
   QStringList leftJoins;
   QStringList columns;
 
-  columns << "t.*"; // columns from the main layer
-
   // look for the uid
   const QgsFields& fields = layer->dataProvider()->fields();
   {
@@ -47,14 +46,21 @@ QgsVirtualLayerDefinition QgsVirtualLayerDefinitionUtils::fromJoinedLayer( QgsVe
       def.setUid( uid );
     }
   }
+  Q_FOREACH ( const QgsField& f, layer->dataProvider()->fields() )
+  {
+    columns << "t." + f.name();
+  }
 
   int joinIdx = 0;
   Q_FOREACH ( const QgsVectorJoinInfo& join, layer->vectorJoins() )
   {
     QString joinName = QString( "j%1" ).arg( ++joinIdx );
-    QString prefix = join.prefix.isEmpty() ? layer->name() + "_" : join.prefix;
+    QgsVectorLayer* joinedLayer = static_cast<QgsVectorLayer*>( QgsMapLayerRegistry::instance()->mapLayer( join.joinLayerId ) );
+    if ( !joinedLayer )
+      continue;
+    QString prefix = join.prefix.isEmpty() ? joinedLayer->name() + "_" : join.prefix;
 
-    leftJoins << QString( "LEFT JOIN %1 AS %2 ON t.\"%3\"=%2.\"%5\"" ).arg( join.joinLayerId, joinName, join.joinFieldName, join.targetFieldName );
+    leftJoins << QString( "LEFT JOIN %1 AS %2 ON t.\"%5\"=%2.\"%3\"" ).arg( join.joinLayerId, joinName, join.joinFieldName, join.targetFieldName );
     if ( join.joinFieldNamesSubset() )
     {
       Q_FOREACH ( const QString& f, *join.joinFieldNamesSubset() )
@@ -64,8 +70,10 @@ QgsVirtualLayerDefinition QgsVirtualLayerDefinitionUtils::fromJoinedLayer( QgsVe
     }
     else
     {
-      Q_FOREACH ( const QgsField& f, layer->dataProvider()->fields() )
+      Q_FOREACH ( const QgsField& f, joinedLayer->fields() )
       {
+        if ( f.name() == join.joinFieldName )
+          continue;
         columns << joinName + "." + f.name() + " AS " + prefix + f.name();
       }
     }

tests/src/python/test_provider_virtual.py

@@ -22,8 +22,10 @@
                        QgsMapLayerRegistry,
                        QgsRectangle,
                        QgsVirtualLayerDefinition,
+                       QgsVirtualLayerDefinitionUtils,
                        QgsWKBTypes,
-                       QgsProject
+                       QgsProject,
+                       QgsVectorJoinInfo
                        )
 
 from qgis.testing import start_app, unittest
@@ -731,6 +733,59 @@ def test_query_with_accents(self):
         ids = [f.id() for f in vl2.getFeatures()]
         self.assertEqual(ids, [])
 
+    def test_joined_layers_conversion(self):
+        v1 = QgsVectorLayer("Point?field=id:integer&field=b_id:integer&field=c_id:integer&field=name:string", "A", "memory")
+        self.assertEqual(v1.isValid(), True)
+        v2 = QgsVectorLayer("Point?field=id:integer&field=bname:string&field=bfield:integer", "B", "memory")
+        self.assertEqual(v2.isValid(), True)
+        v3 = QgsVectorLayer("Point?field=id:integer&field=cname:string", "C", "memory")
+        self.assertEqual(v3.isValid(), True)
+        QgsMapLayerRegistry.instance().addMapLayers([v1, v2, v3])
+        joinInfo = QgsVectorJoinInfo()
+        joinInfo.targetFieldName = "b_id"
+        joinInfo.joinLayerId = v2.id()
+        joinInfo.joinFieldName = "id"
+        #joinInfo.prefix = "B_";
+        v1.addJoin(joinInfo)
+        self.assertEqual(len(v1.fields()), 6)
+
+        df = QgsVirtualLayerDefinitionUtils.fromJoinedLayer(v1)
+        self.assertEqual(df.query(), 'SELECT t.rowid AS uid, t.id, t.b_id, t.c_id, t.name, j1.bname AS B_bname, j1.bfield AS B_bfield FROM {} AS t LEFT JOIN {} AS j1 ON t."b_id"=j1."id"'.format(v1.id(), v2.id()))
+
+        # with a field subset
+        v1.removeJoin(v2.id())
+        joinInfo.setJoinFieldNamesSubset(["bname"])
+        v1.addJoin(joinInfo)
+        self.assertEqual(len(v1.fields()), 5)
+        df = QgsVirtualLayerDefinitionUtils.fromJoinedLayer(v1)
+        self.assertEqual(df.query(), 'SELECT t.rowid AS uid, t.id, t.b_id, t.c_id, t.name, j1.bname AS B_bname FROM {} AS t LEFT JOIN {} AS j1 ON t."b_id"=j1."id"'.format(v1.id(), v2.id()))
+        joinInfo.setJoinFieldNamesSubset(None)
+
+        # add a table prefix to the join
+        v1.removeJoin(v2.id())
+        joinInfo.prefix = "BB_"
+        v1.addJoin(joinInfo)
+        self.assertEqual(len(v1.fields()), 6)
+        df = QgsVirtualLayerDefinitionUtils.fromJoinedLayer(v1)
+        self.assertEqual(df.query(), 'SELECT t.rowid AS uid, t.id, t.b_id, t.c_id, t.name, j1.bname AS BB_bname, j1.bfield AS BB_bfield FROM {} AS t LEFT JOIN {} AS j1 ON t."b_id"=j1."id"'.format(v1.id(), v2.id()))
+        joinInfo.prefix = ""
+        v1.removeJoin(v2.id())
+        v1.addJoin(joinInfo)
+
+        # add another join
+        joinInfo2 = QgsVectorJoinInfo()
+        joinInfo2.targetFieldName = "c_id"
+        joinInfo2.joinLayerId = v3.id()
+        joinInfo2.joinFieldName = "id"
+        v1.addJoin(joinInfo2)
+        self.assertEqual(len(v1.fields()), 7)
+        df = QgsVirtualLayerDefinitionUtils.fromJoinedLayer(v1)
+        self.assertEqual(df.query(), ('SELECT t.rowid AS uid, t.id, t.b_id, t.c_id, t.name, j1.bname AS B_bname, j1.bfield AS B_bfield, j2.cname AS C_cname FROM {} AS t ' +
+                                      'LEFT JOIN {} AS j1 ON t."b_id"=j1."id" ' +
+                                      'LEFT JOIN {} AS j2 ON t."c_id"=j2."id"').format(v1.id(), v2.id(), v3.id()))
+
+        QgsMapLayerRegistry.instance().removeMapLayers([v1, v2, v3])
+
 
 if __name__ == '__main__':
     unittest.main()