public Func <int, bool> GetDependencies(Func <int, bool> activeOutput)
{
if (Enumerable.Range(0, _parent.AddedSchema.Columns.Length).Any(activeOutput))
{
// If any output column is requested, then we activate all input columns that we need.
return(_typedSrc.GetDependencies(col => false));
}
// Otherwise, we need no input.
return(col => false);
}
public DataViewRowCursor GetRowCursor(IEnumerable <DataViewSchema.Column> columnsNeeded, Random rand = null)
{
Host.AssertValueOrNull(rand);
var predicate = RowCursorUtils.FromColumnsToPredicate(columnsNeeded, Schema);
Func <int, bool> inputPred = TypedSrc.GetDependencies(predicate);
var inputCols = Input.Schema.Where(x => inputPred(x.Index));
var input = Input.GetRowCursor(inputCols, rand);
return(GetRowCursorCore(input, Utils.BuildArray(Input.Schema.Count, inputCols)));
}