func (f *Field) RowTopN(n uint64, row *PQLRowQuery) *PQLRowQuery {
	q := NewPQLRowQuery(fmt.Sprintf("TopN(%s,%s,n=%d)",
		f.name, row.serialize(), n), f.index, nil)
	return q
}
func (f *Field) RowTopN(n uint64, row *PQLRowQuery) *PQLRowQuery {
	q := NewPQLRowQuery(fmt.Sprintf("TopN(%s,%s,n=%d)",
		f.name, row.serialize(), n), f.index, nil)
	return q
}
// RowTopN creates a TopN query with the given item count and row.
// This variant supports customizing the row query.