func (f *Field) NotNull() *PQLRowQuery {
	text := fmt.Sprintf("Range(%s != null)", f.name)
	q := NewPQLRowQuery(text, f.index, nil)
	q.hasKeys = f.options.keys || f.index.options.keys
	return q
}
func (f *Field) NotNull() *PQLRowQuery {
	text := fmt.Sprintf("Range(%s != null)", f.name)
	q := NewPQLRowQuery(text, f.index, nil)
	q.hasKeys = f.options.keys || f.index.options.keys
	return q
}
// NotNull creates a not equal to null query.