Use intermediate vars instead of complex expression in CreateLocalCollectionProjectionExpression()

Author: SergeiPavlov

Orm/Xtensive.Orm/Orm/Linq/Translator.Expressions.cs

@@ -1594,10 +1594,12 @@ private static ProjectionExpression CreateLocalCollectionProjectionExpression(Ty
     {
       var storedEntityType = translator.State.TypeOfEntityStoredInKey;
       var itemToTupleConverter = ItemToTupleConverter.BuildConverter(itemType, storedEntityType, value, translator.context.Model, sourceExpression);
-      var rsHeader = new RecordSetHeader(
-        itemToTupleConverter.TupleDescriptor,
-        itemToTupleConverter.TupleDescriptor.Select(x => new SystemColumn(translator.context.GetNextColumnAlias(), 0, x)).Cast<Column>().ToArray(itemToTupleConverter.TupleDescriptor.Count)
-      );
+      var tupleDescriptor = itemToTupleConverter.TupleDescriptor;
+      var columns = tupleDescriptor
+        .Select(x => new SystemColumn(translator.context.GetNextColumnAlias(), 0, x))
+        .Cast<Column>()
+        .ToArray(tupleDescriptor.Count);
+      var rsHeader = new RecordSetHeader(tupleDescriptor, columns);
       var rawProvider = new RawProvider(rsHeader, itemToTupleConverter.GetEnumerable());
       var recordset = new StoreProvider(rawProvider);
       var itemProjector = new ItemProjectorExpression(itemToTupleConverter.Expression, recordset, translator.context);