[layouts] Fix inefficient filtering in attribute tables

nyalldawson · nyalldawson · commit e3c1d18f3aaa · 2019-01-05T07:31:27.000+10:00
Set the expression filter on the request itself, rather than looping through all features and testing on the filter. This allows providers to hand off the filtering to the underlying datasource, and utilise indices/etc where available. Fixes #20908
diff --git a/src/core/layout/qgslayoutitemattributetable.cpp b/src/core/layout/qgslayoutitemattributetable.cpp
@@ -399,6 +399,8 @@ bool QgsLayoutItemAttributeTable::getTableContents( QgsLayoutTableContents &cont
   QgsExpressionContext context = createExpressionContext();
   context.setFields( layer->fields() );
 
+  QgsFeatureRequest req;
+
   //prepare filter expression
   std::unique_ptr<QgsExpression> filterExpression;
   bool activeFilter = false;
@@ -408,6 +410,7 @@ bool QgsLayoutItemAttributeTable::getTableContents( QgsLayoutTableContents &cont
     if ( !filterExpression->hasParserError() )
     {
       activeFilter = true;
+      req.setFilterExpression( mFeatureFilter );
     }
   }
 
@@ -431,8 +434,6 @@ bool QgsLayoutItemAttributeTable::getTableContents( QgsLayoutTableContents &cont
     }
   }
 
-  QgsFeatureRequest req;
-
   if ( mSource == QgsLayoutItemAttributeTable::RelationChildren )
   {
     QgsRelation relation = mLayout->project()->relationManager()->relation( mRelationId );

Original file line number	Diff line number	Diff line change
`@@ -399,6 +399,8 @@ bool QgsLayoutItemAttributeTable::getTableContents( QgsLayoutTableContents &cont`
`399`	`399`	`QgsExpressionContext context = createExpressionContext();`
`400`	`400`	`context.setFields( layer->fields() );`
`401`	`401`
	`402`	`+ QgsFeatureRequest req;`
	`403`	`+`
`402`	`404`	`//prepare filter expression`
`403`	`405`	`std::unique_ptr<QgsExpression> filterExpression;`
`404`	`406`	`bool activeFilter = false;`
`@@ -408,6 +410,7 @@ bool QgsLayoutItemAttributeTable::getTableContents( QgsLayoutTableContents &cont`
`408`	`410`	`if ( !filterExpression->hasParserError() )`
`409`	`411`	`{`
`410`	`412`	`activeFilter = true;`
	`413`	`+ req.setFilterExpression( mFeatureFilter );`
`411`	`414`	`}`
`412`	`415`	`}`
`413`	`416`
`@@ -431,8 +434,6 @@ bool QgsLayoutItemAttributeTable::getTableContents( QgsLayoutTableContents &cont`
`431`	`434`	`}`
`432`	`435`	`}`
`433`	`436`
`434`		`- QgsFeatureRequest req;`
`435`		`-`
`436`	`437`	`if ( mSource == QgsLayoutItemAttributeTable::RelationChildren )`
`437`	`438`	`{`
`438`	`439`	`QgsRelation relation = mLayout->project()->relationManager()->relation( mRelationId );`