Use a FilterFids request for vector file writer rather than fetching

nyalldawson · nyalldawson · commit f0d31b03a9bb · 2015-11-05T21:22:16.000+11:00
all features and then testing the feature id when saving selected features For providers such as Postgres this is orders of magnitude faster. Eg, saving 6 selected features from a 800k PostGIS table now takes < 1 second as opposed to ~33 seconds Fix #8334
diff --git a/src/core/qgsvectorfilewriter.cpp b/src/core/qgsvectorfilewriter.cpp
@@ -1982,10 +1982,10 @@ QgsVectorFileWriter::WriterError QgsVectorFileWriter::writeAsVectorFormat( QgsVe
     req.setFlags( QgsFeatureRequest::NoGeometry );
   }
   req.setSubsetOfAttributes( allAttr );
+  if ( onlySelected )
+    req.setFilterFids( layer->selectedFeaturesIds() );
   QgsFeatureIterator fit = layer->getFeatures( req );
 
-  const QgsFeatureIds& ids = layer->selectedFeaturesIds();
-
   //create symbol table if needed
   if ( writer->symbologyExport() != NoSymbology )
   {
@@ -2027,9 +2027,6 @@ QgsVectorFileWriter::WriterError QgsVectorFileWriter::writeAsVectorFormat( QgsVe
   // write all features
   while ( fit.nextFeature( fet ) )
   {
-    if ( onlySelected && !ids.contains( fet.id() ) )
-      continue;
-
     if ( shallTransform )
     {
       try

Original file line number	Diff line number	Diff line change
`@@ -1982,10 +1982,10 @@ QgsVectorFileWriter::WriterError QgsVectorFileWriter::writeAsVectorFormat( QgsVe`
`1982`	`1982`	`req.setFlags( QgsFeatureRequest::NoGeometry );`
`1983`	`1983`	`}`
`1984`	`1984`	`req.setSubsetOfAttributes( allAttr );`
	`1985`	`+ if ( onlySelected )`
	`1986`	`+ req.setFilterFids( layer->selectedFeaturesIds() );`
`1985`	`1987`	`QgsFeatureIterator fit = layer->getFeatures( req );`
`1986`	`1988`
`1987`		`- const QgsFeatureIds& ids = layer->selectedFeaturesIds();`
`1988`		`-`
`1989`	`1989`	`//create symbol table if needed`
`1990`	`1990`	`if ( writer->symbologyExport() != NoSymbology )`
`1991`	`1991`	`{`
`@@ -2027,9 +2027,6 @@ QgsVectorFileWriter::WriterError QgsVectorFileWriter::writeAsVectorFormat( QgsVe`
`2027`	`2027`	`// write all features`
`2028`	`2028`	`while ( fit.nextFeature( fet ) )`
`2029`	`2029`	`{`
`2030`		`- if ( onlySelected && !ids.contains( fet.id() ) )`
`2031`		`- continue;`
`2032`		`-`
`2033`	`2030`	`if ( shallTransform )`
`2034`	`2031`	`{`
`2035`	`2032`	`try`