Immediately liberate connection of expression value gatherer

This fixes a deadlock The iterator as a member as previously implemented kept connections occupied for as long as the gatherer existed. This could lead to a situation, where all connections have been reserved from finished gatherers which were waiting to be deleted (through deleteLater), but deleteLater would never happen because the main thread was waiting for a connection to become available. Fixes #37496
qgis · Jul 1, 2020 · 9360515 · 9360515
1 parent 2a786ae
commit 9360515
Showing 1 changed file with 2 additions and 3 deletions.
diff --git a/src/core/qgsfeatureexpressionvaluesgatherer.h b/src/core/qgsfeatureexpressionvaluesgatherer.h
@@ -91,7 +91,7 @@ class QgsFeatureExpressionValuesGatherer: public QThread
     {
       mWasCanceled = false;
 
-      mIterator = mSource->getFeatures( mRequest );
+      QgsFeatureIterator iterator = mSource->getFeatures( mRequest );
 
       mDisplayExpression.prepare( &mExpressionContext );
 
@@ -100,7 +100,7 @@ class QgsFeatureExpressionValuesGatherer: public QThread
       for ( const QString &fieldName : qgis::as_const( mIdentifierFields ) )
         attributeIndexes << mSource->fields().indexOf( fieldName );
 
-      while ( mIterator.nextFeature( feature ) )
+      while ( iterator.nextFeature( feature ) )
       {
         mExpressionContext.setFeature( feature );
         QVariantList attributes;
@@ -165,7 +165,6 @@ class QgsFeatureExpressionValuesGatherer: public QThread
     QgsExpression mDisplayExpression;
     QgsExpressionContext mExpressionContext;
     QgsFeatureRequest mRequest;
-    QgsFeatureIterator mIterator;
     bool mWasCanceled = false;
     mutable QMutex mCancelMutex;
     QStringList mIdentifierFields;