internal static List <SelectExpression> Gather(Expression source)
{
RedundantSubqueryGatherer gatherer = new RedundantSubqueryGatherer();
gatherer.Visit(source);
return(gatherer.redundant);
}
protected override Expression VisitProjection(ProjectionExpression proj)
{
proj = (ProjectionExpression)base.VisitProjection(proj);
if (proj.Select.From is SelectExpression)
{
List <SelectExpression> redundant = RedundantSubqueryGatherer.Gather(proj.Select);
if (redundant != null)
{
proj = SubqueryRemover.Remove(proj, redundant);
}
}
return(proj);
}
protected override Expression VisitSelect(SelectExpression select)
{
select = (SelectExpression)base.VisitSelect(select);
// first remove all purely redundant subqueries
List <SelectExpression> redundant = RedundantSubqueryGatherer.Gather(select.From);
if (redundant != null)
{
select = SubqueryRemover.Remove(select, redundant);
}
return(select);
}