Merge pull request #42412 from elpaso/optimization-ogr-avoid-double-l…

…oad-fields-call

Prevent double expensive calls to loadFields in OGR

src/core/providers/ogr/qgsogrprovider.cpp

@@ -2306,6 +2306,8 @@ bool QgsOgrProvider::_setSubsetString( const QString &theSQL, bool updateFeature
   if ( theSQL == mSubsetString && mFeaturesCounted != QgsVectorDataProvider::Uncounted )
     return true;
 
+  const bool subsetStringHasChanged { theSQL != mSubsetString };
+
   if ( !theSQL.isEmpty() )
   {
     QMutex *mutex = nullptr;
@@ -2387,10 +2389,11 @@ bool QgsOgrProvider::_setSubsetString( const QString &theSQL, bool updateFeature
 
   mRefreshFeatureCount = updateFeatureCount;
 
-  // check the validity of the layer
-  QgsDebugMsgLevel( QStringLiteral( "checking validity" ), 4 );
-  loadFields();
-  QgsDebugMsgLevel( QStringLiteral( "Done checking validity" ), 4 );
+  // check the validity of the layer if subset string has changed
+  if ( subsetStringHasChanged )
+  {
+    loadFields();
+  }
 
   invalidateCachedExtent( false );
 
@@ -7340,4 +7343,3 @@ QgsProviderMetadata::ProviderCapabilities QgsOgrProviderMetadata::providerCapabi
   return FileBasedUris;
 }
 ///@endcond
-