protected override Expression VisitSelect(SelectExpression node)
{
// visit column projection first
ReadOnlyCollection<ColumnDeclaration> columns = node.Columns;
List<ColumnDeclaration> alternate = null;
for (Int32 i = 0, n = node.Columns.Count; i < n; i++)
{
ColumnDeclaration decl = node.Columns[i];
if (IsColumnUsed(node.Alias, decl.Name))
{
Expression expr = Visit(decl.Expression);
if (expr != decl.Expression)
{
decl = new ColumnDeclaration(decl.Name, expr);
}
}
else
{
decl = null; // null means it gets omitted
}
if (decl != node.Columns[i] && alternate == null)
{
alternate = new List<ColumnDeclaration>();
for (Int32 j = 0; j < i; j++)
{
alternate.Add(node.Columns[j]);
}
}
if (decl != null && alternate != null)
{
alternate.Add(decl);
}
}
if (alternate != null)
{
columns = alternate.AsReadOnly();
}
Expression take = Visit(node.Take);
ReadOnlyCollection<Expression> groupbys = VisitExpressionList(node.GroupBy);
ReadOnlyCollection<OrderByExpression> orderbys = VisitOrderBy(node.OrderBy);
Expression where = Visit(node.Where);
Expression from = Visit(node.From);
ClearColumnsUsed(node.Alias);
if (columns != node.Columns
|| take != node.Take
|| orderbys != node.OrderBy
|| groupbys != node.GroupBy
|| where != node.Where
|| from != node.From)
{
node = new SelectExpression(node.Alias, columns, from, where, orderbys, groupbys, take);
}
return node;
}
// protected override methods
protected override Expression VisitSelect(SelectExpression node)
{
node = (SelectExpression) base.VisitSelect(node);
if (_lookup.Contains(node.Alias))
{
var aggColumns = new List<ColumnDeclaration>(node.Columns);
foreach (AggregateSubqueryExpression ae in _lookup[node.Alias])
{
String name = "agg" + aggColumns.Count;
var cd = new ColumnDeclaration(name, ae.AggregateInGroupSelect);
_map.Add(ae, new ColumnExpression(ae.Type, ae.GroupByAlias, name));
aggColumns.Add(cd);
}
return new SelectExpression(node.Alias, aggColumns, node.From, node.Where, node.OrderBy, node.GroupBy,
node.Take);
}
return node;
}