code: @Override
    public MtasSpanQuery rewrite(IndexReader reader) throws IOException {
      MtasSpanQuery newQ1 = (MtasSpanQuery) q1.rewrite(reader);
      MtasSpanQuery newQ2 = (MtasSpanQuery) q2.rewrite(reader);
      if (!newQ1.equals(q1) || !newQ2.equals(q2)) {
        return new MtasSpanNotQuery(newQ1, newQ2).rewrite(reader);
      } else {
        baseQuery = (SpanNotQuery) baseQuery.rewrite(reader);
        return super.rewrite(reader);
      }
    }
docs: /*
  (non-Javadoc)
  
  @see mtas.search.spans.util.MtasSpanQuery#rewrite(org.apache.lucene.index.
  IndexReader)