don't set relevant fields for VRT data sources when filtering for a rectangle.

OGR might need attributes otherwise considered irrelevant to construct the
geometry to filter against (fixes #11223)

Author: jef-n

src/providers/ogr/qgsogrfeatureiterator.cpp

@@ -59,10 +59,17 @@ QgsOgrFeatureIterator::QgsOgrFeatureIterator( QgsOgrFeatureSource* source, bool
     mSubsetStringSet = true;
   }
 
-  // make sure we fetch just relevant fields
   mFetchGeometry = ( mRequest.filterType() == QgsFeatureRequest::FilterRect ) || !( mRequest.flags() & QgsFeatureRequest::NoGeometry );
   QgsAttributeList attrs = ( mRequest.flags() & QgsFeatureRequest::SubsetOfAttributes ) ? mRequest.subsetOfAttributes() : mSource->mFields.allAttributesList();
-  QgsOgrUtils::setRelevantFields( ogrLayer, mSource->mFields.count(), mFetchGeometry, attrs );
+
+  // make sure we fetch just relevant fields
+  // unless it's a VRT data source filtered by geometry as we don't know which
+  // attributes make up the geometry and OGR won't fetch them to evaluate the
+  // filter if we choose to ignore them (fixes #11223)
+  if ( mSource->mDriverName != "OGR_VRT" || mRequest.filterType() != QgsFeatureRequest::FilterRect )
+  {
+    QgsOgrUtils::setRelevantFields( ogrLayer, mSource->mFields.count(), mFetchGeometry, attrs );
+  }
 
   // spatial query to select features
   if ( mRequest.filterType() == QgsFeatureRequest::FilterRect )
@@ -337,6 +344,7 @@ QgsOgrFeatureSource::QgsOgrFeatureSource( const QgsOgrProvider* p )
   mSubsetString = p->mSubsetString;
   mEncoding = p->mEncoding; // no copying - this is a borrowed pointer from Qt
   mFields = p->mAttributeFields;
+  mDriverName = p->ogrDriverName;
   mOgrGeometryTypeFilter = wkbFlatten( p->mOgrGeometryTypeFilter );
 }
 

src/providers/ogr/qgsogrfeatureiterator.h

@@ -38,6 +38,7 @@ class QgsOgrFeatureSource : public QgsAbstractFeatureSource
     QTextCodec* mEncoding;
     QgsFields mFields;
     OGRwkbGeometryType mOgrGeometryTypeFilter;
+    QString mDriverName;
 
     friend class QgsOgrFeatureIterator;
 };