protected override Expression VisitScalar(ScalarExpression scalar)
{
scalar = (ScalarExpression)base.VisitScalar(scalar);
if (_currentGroupBys != null && _currentFrom != null)
{
if (scalar.Query is SelectExpression innerSelect && SourcesAreEqual(_currentFrom, innerSelect.From))
{
var groupedColumns = GroupedColumnGatherer.Gather(innerSelect.Where);
if (groupedColumns?.SequenceEqual(_currentGroupBys) ?? false)
{
var innerAggExpr = (AggregateExpression)innerSelect.Columns[0].Expression;
if (innerAggExpr.Argument == null)
{
return(new AggregateExpression(
innerAggExpr.Type,
innerAggExpr.AggregateType,
null,
innerAggExpr.IsDistict
));
}
else if (innerAggExpr.Argument is ColumnExpression column)
{
var source = GetSource(_currentFrom, innerSelect.From, column.Alias);
return(new AggregateExpression(
innerAggExpr.Type,
innerAggExpr.AggregateType,
new ColumnExpression(column.Type, source.Alias, column.Name),
innerAggExpr.IsDistict
));
}
}
}
}
return(scalar);
}
public static List <ColumnExpression> Gather(Expression expression)
{
var g = new GroupedColumnGatherer();
g.Visit(expression);
return(g._columns);
}