func (b Column) Less(other Record) bool {
	if ob, ok := other.(Column); ok {
		if b.RowID == ob.RowID {
			return b.ColumnID < ob.ColumnID
		}
		return b.RowID < ob.RowID
	}
	return false
}
func (b Column) Less(other Record) bool {
	if ob, ok := other.(Column); ok {
		if b.RowID == ob.RowID {
			return b.ColumnID < ob.ColumnID
		}
		return b.RowID < ob.RowID
	}
	return false
}
// Less returns true if this column sorts before the given Record.