code: func (v *view) rangeOp(op pql.Token, bitDepth uint, predicate uint64) (*Row, error) {
  	r := NewRow()
  	for _, frag := range v.allFragments() {
  		other, err := frag.rangeOp(op, bitDepth, predicate)
  		if err != nil {
  			return nil, err
  		}
  		r = r.Union(other)
  	}
  	return r, nil
  }
docs: // rangeOp returns rows with a field value encoding matching the predicate.