Fix wrong attr values in joined fields

If the joined layer has field names that collide with already existing fields, these fields from the joined layer are dropped. However, this situation was not handled in the code, as the real joined field attr index is not being used, but indices starting from 0, 1, 2 for each of the joined fields. For example: "joined" layer has fields "id", "name" and "descr"; "source" layer has fields "id", "name", "joined_id" Then "id" and "name" column from "joined" will be discarded, but the the value for "descr" would not be taken from attribute index 2, but index 2. Fix #26652
qgis · Jan 27, 2021 · 3b54697 · 3b54697
1 parent d821f0a
commit 3b54697
Showing 1 changed file with 13 additions and 17 deletions.
diff --git a/src/core/vector/qgsvectorlayerfeatureiterator.cpp b/src/core/vector/qgsvectorlayerfeatureiterator.cpp
@@ -1076,15 +1076,24 @@ void QgsVectorLayerFeatureIterator::FetchJoinInfo::addJoinedAttributesDirect( Qg
     subsetString += '=' + v;
   }
 
+  QList<int> joinedAttributeIndices;
+
   // maybe user requested just a subset of layer's attributes
   // so we do not have to cache everything
-  QVector<int> subsetIndices;
   if ( joinInfo->hasSubset() )
   {
     const QStringList subsetNames = QgsVectorLayerJoinInfo::joinFieldNamesSubset( *joinInfo );
-    subsetIndices = QgsVectorLayerJoinBuffer::joinSubsetIndices( joinLayer, subsetNames );
+    QVector<int> subsetIndices = QgsVectorLayerJoinBuffer::joinSubsetIndices( joinLayer, subsetNames );
+    joinedAttributeIndices = attributes.toSet().intersect( subsetIndices.toList().toSet() ).toList();
+  }
+  else
+  {
+    joinedAttributeIndices = attributes.toVector().toList();
   }
 
+  // we don't need the join field, it is already present in the other table
+  joinedAttributeIndices.removeAll( joinField );
+
   // select (no geometry)
   QgsFeatureRequest request;
   request.setFlags( QgsFeatureRequest::NoGeometry );
@@ -1099,22 +1108,9 @@ void QgsVectorLayerFeatureIterator::FetchJoinInfo::addJoinedAttributesDirect( Qg
   {
     int index = indexOffset;
     QgsAttributes attr = fet.attributes();
-    if ( joinInfo->hasSubset() )
-    {
-      for ( int i = 0; i < subsetIndices.count(); ++i )
-        f.setAttribute( index++, attr.at( subsetIndices.at( i ) ) );
-    }
-    else
-    {
-      // use all fields except for the one used for join (has same value as exiting field in target layer)
-      for ( int i = 0; i < attr.count(); ++i )
-      {
-        if ( i == joinField )
-          continue;
 
-        f.setAttribute( index++, attr.at( i ) );
-      }
-    }
+    for ( int i = 0; i < joinedAttributeIndices.count(); ++i )
+      f.setAttribute( index++, attr.at( joinedAttributeIndices.at( i ) ) );
   }
   else
   {