code: func (r *Reader) Postings(name, value string) (Postings, error) {
  	e, ok := r.postings[name]
  	if !ok {
  		return EmptyPostings(), nil
  	}
  	off, ok := e[value]
  	if !ok {
  		return EmptyPostings(), nil
  	}
  	d := encoding.NewDecbufAt(r.b, int(off), castagnoliTable)
  	if d.Err() != nil {
  		return nil, errors.Wrap(d.Err(), "get postings entry")
  	}
  	_, p, err := r.dec.Postings(d.Get())
  	if err != nil {
  		return nil, errors.Wrap(err, "decode postings")
  	}
  	return p, nil
  }
docs: // Postings returns a postings list for the given label pair.