public static HashSet <string> Gather(Expression source)
{
AliasesProduced ap = new AliasesProduced();
ap.Visit(source);
return(ap._aliases);
}
protected override Expression VisitSelect(SelectExpression select)
{
bool saveIsOuterMostSelect = _isOuterMostSelect;
try
{
_isOuterMostSelect = false;
select = (SelectExpression)base.VisitSelect(select);
bool hasOrderBy = select.OrderBy != null && select.OrderBy.Count > 0;
if (hasOrderBy)
{
PrependOrderings(select.OrderBy);
}
bool canHaveOrderBy = saveIsOuterMostSelect;
bool canPassOnOrderings = !saveIsOuterMostSelect;
IEnumerable <OrderExpression> orderings = (canHaveOrderBy) ? _gatheredOrderings : null;
ReadOnlyCollection <ColumnDeclaration> columns = select.Columns;
if (_gatheredOrderings != null)
{
if (canPassOnOrderings)
{
HashSet <string> producedAliases = AliasesProduced.Gather(select.From);
// reproject order expressions using this select’s alias so the outer select will have properly formed expressions
BindResult project = RebindOrderings(_gatheredOrderings, select.Alias, producedAliases, select.Columns);
_gatheredOrderings = project.Orderings;
columns = project.Columns;
}
else
{
_gatheredOrderings = null;
}
}
if (orderings != select.OrderBy || columns != select.Columns)
{
select = new SelectExpression(select.Alias, columns, select.From, select.Where, select.GroupBy, select.Having, orderings, select.Offset, select.Limit, select.IsDistinct);
}
return(select);
}
finally
{
_isOuterMostSelect = saveIsOuterMostSelect;
}
}