Fix #9139 - Don't crash on MSSQL relations

src/providers/mssql/qgsmssqlfeatureiterator.cpp

@@ -97,6 +97,7 @@ void QgsMssqlFeatureIterator::BuildStatement( const QgsFeatureRequest& request )
       mAttributesToFetch.append( i );
     }
   }
+
   // get fid col if not yet required
   if ( mFidCol == -1 && !mSource->mFidColName.isEmpty() )
   {
@@ -107,7 +108,7 @@ void QgsMssqlFeatureIterator::BuildStatement( const QgsFeatureRequest& request )
     ++fieldCount;
   }
   // get geometry col
-  if ( !( request.flags() & QgsFeatureRequest::NoGeometry ) && !mSource->mGeometryColName.isEmpty() )
+  if ( !( request.flags() & QgsFeatureRequest::NoGeometry ) && mSource->isSpatial() )
   {
     if ( fieldCount != 0 )
       mStatement += ",";
@@ -124,7 +125,7 @@ void QgsMssqlFeatureIterator::BuildStatement( const QgsFeatureRequest& request )
 
   bool filterAdded = false;
   // set spatial filter
-  if ( request.filterType() & QgsFeatureRequest::FilterRect )
+  if ( request.filterType() & QgsFeatureRequest::FilterRect && isSpatial() )
   {
     // polygons should be CCW for SqlGeography
     QString r;
@@ -162,6 +163,7 @@ void QgsMssqlFeatureIterator::BuildStatement( const QgsFeatureRequest& request )
       mStatement += " and (" + mSource->mSqlWhereClause + ")";
   }
 
+//  QgsDebugMsg( mStatement );
   if ( fieldCount == 0 )
   {
     QgsDebugMsg( "QgsMssqlProvider::select no fields have been requested" );

src/providers/mssql/qgsmssqlfeatureiterator.h

@@ -62,6 +62,9 @@ class QgsMssqlFeatureSource : public QgsAbstractFeatureSource
     // SQL statement used to limit the features retrieved
     QString mSqlWhereClause;
 
+    // Return True if this feature source has spatial attributes.
+    bool isSpatial() { return !mGeometryColName.isEmpty() || !mGeometryColType.isEmpty(); }
+
     friend class QgsMssqlFeatureIterator;
 };
 
@@ -111,6 +114,9 @@ class QgsMssqlFeatureIterator : public QgsAbstractFeatureIteratorFromSource<QgsM
 
     // for parsing sql geometries
     QgsMssqlGeometryParser mParser;
+
+    // Return True of the geometry column was found when parsing the columns.
+    bool isSpatial() { return mGeometryCol > -1; }
 };
 
 #endif // QGSMSSQLFEATUREITERATOR_H