public NamedList buildResponse() {
      NamedList<Object> response = new SimpleOrderedMap<>();

      // determine if we are going index or count sort
      boolean sort =
          !TermsParams.TERMS_SORT_INDEX.equals(
              params.get(TermsParams.TERMS_SORT, TermsParams.TERMS_SORT_COUNT));

      // init minimum frequency
      long freqmin = 1;
      String s = params.get(TermsParams.TERMS_MINCOUNT);
      if (s != null) freqmin = Long.parseLong(s);

      // init maximum frequency, default to max int
      long freqmax = -1;
      s = params.get(TermsParams.TERMS_MAXCOUNT);
      if (s != null) freqmax = Long.parseLong(s);
      if (freqmax < 0) {
        freqmax = Long.MAX_VALUE;
      }

      // init limit, default to max int
      long limit = 10;
      s = params.get(TermsParams.TERMS_LIMIT);
      if (s != null) limit = Long.parseLong(s);
      if (limit < 0) {
        limit = Long.MAX_VALUE;
      }

      // loop though each field we want terms from
      for (String key : fieldmap.keySet()) {
        NamedList<Number> fieldterms = new SimpleOrderedMap<>();
        TermsResponse.Term[] data = null;
        if (sort) {
          data = getCountSorted(fieldmap.get(key));
        } else {
          data = getLexSorted(fieldmap.get(key));
        }

        // loop though each term until we hit limit
        int cnt = 0;
        for (TermsResponse.Term tc : data) {
          if (tc.getFrequency() >= freqmin && tc.getFrequency() <= freqmax) {
            fieldterms.add(tc.getTerm(), num(tc.getFrequency()));
            cnt++;
          }

          if (cnt >= limit) {
            break;
          }
        }

        response.add(key, fieldterms);
      }

      return response;
    }
  @Override
  public void process(ResponseBuilder rb) throws IOException {
    SolrParams params = rb.req.getParams();
    if (!params.getBool(TermsParams.TERMS, false)) return;

    String[] fields = params.getParams(TermsParams.TERMS_FIELD);

    NamedList<Object> termsResult = new SimpleOrderedMap<>();
    rb.rsp.add("terms", termsResult);

    if (fields == null || fields.length == 0) return;

    int limit = params.getInt(TermsParams.TERMS_LIMIT, 10);
    if (limit < 0) {
      limit = Integer.MAX_VALUE;
    }

    String lowerStr = params.get(TermsParams.TERMS_LOWER);
    String upperStr = params.get(TermsParams.TERMS_UPPER);
    boolean upperIncl = params.getBool(TermsParams.TERMS_UPPER_INCLUSIVE, false);
    boolean lowerIncl = params.getBool(TermsParams.TERMS_LOWER_INCLUSIVE, true);
    boolean sort =
        !TermsParams.TERMS_SORT_INDEX.equals(
            params.get(TermsParams.TERMS_SORT, TermsParams.TERMS_SORT_COUNT));
    int freqmin = params.getInt(TermsParams.TERMS_MINCOUNT, 1);
    int freqmax = params.getInt(TermsParams.TERMS_MAXCOUNT, UNLIMITED_MAX_COUNT);
    if (freqmax < 0) {
      freqmax = Integer.MAX_VALUE;
    }
    String prefix = params.get(TermsParams.TERMS_PREFIX_STR);
    String regexp = params.get(TermsParams.TERMS_REGEXP_STR);
    Pattern pattern = regexp != null ? Pattern.compile(regexp, resolveRegexpFlags(params)) : null;

    boolean raw = params.getBool(TermsParams.TERMS_RAW, false);

    final AtomicReader indexReader = rb.req.getSearcher().getAtomicReader();
    Fields lfields = indexReader.fields();

    for (String field : fields) {
      NamedList<Integer> fieldTerms = new NamedList<>();
      termsResult.add(field, fieldTerms);

      Terms terms = lfields == null ? null : lfields.terms(field);
      if (terms == null) {
        // no terms for this field
        continue;
      }

      FieldType ft = raw ? null : rb.req.getSchema().getFieldTypeNoEx(field);
      if (ft == null) ft = new StrField();

      // prefix must currently be text
      BytesRef prefixBytes = prefix == null ? null : new BytesRef(prefix);

      BytesRef upperBytes = null;
      if (upperStr != null) {
        upperBytes = new BytesRef();
        ft.readableToIndexed(upperStr, upperBytes);
      }

      BytesRef lowerBytes;
      if (lowerStr == null) {
        // If no lower bound was specified, use the prefix
        lowerBytes = prefixBytes;
      } else {
        lowerBytes = new BytesRef();
        if (raw) {
          // TODO: how to handle binary? perhaps we don't for "raw"... or if the field exists
          // perhaps we detect if the FieldType is non-character and expect hex if so?
          lowerBytes = new BytesRef(lowerStr);
        } else {
          lowerBytes = new BytesRef();
          ft.readableToIndexed(lowerStr, lowerBytes);
        }
      }

      TermsEnum termsEnum = terms.iterator(null);
      BytesRef term = null;

      if (lowerBytes != null) {
        if (termsEnum.seekCeil(lowerBytes) == TermsEnum.SeekStatus.END) {
          termsEnum = null;
        } else {
          term = termsEnum.term();
          // Only advance the enum if we are excluding the lower bound and the lower Term actually
          // matches
          if (lowerIncl == false && term.equals(lowerBytes)) {
            term = termsEnum.next();
          }
        }
      } else {
        // position termsEnum on first term
        term = termsEnum.next();
      }

      int i = 0;
      BoundedTreeSet<CountPair<BytesRef, Integer>> queue =
          (sort ? new BoundedTreeSet<CountPair<BytesRef, Integer>>(limit) : null);
      CharsRef external = new CharsRef();
      while (term != null && (i < limit || sort)) {
        boolean externalized = false; // did we fill in "external" yet for this term?

        // stop if the prefix doesn't match
        if (prefixBytes != null && !StringHelper.startsWith(term, prefixBytes)) break;

        if (pattern != null) {
          // indexed text or external text?
          // TODO: support "raw" mode?
          ft.indexedToReadable(term, external);
          externalized = true;
          if (!pattern.matcher(external).matches()) {
            term = termsEnum.next();
            continue;
          }
        }

        if (upperBytes != null) {
          int upperCmp = term.compareTo(upperBytes);
          // if we are past the upper term, or equal to it (when don't include upper) then stop.
          if (upperCmp > 0 || (upperCmp == 0 && !upperIncl)) break;
        }

        // This is a good term in the range.  Check if mincount/maxcount conditions are satisfied.
        int docFreq = termsEnum.docFreq();
        if (docFreq >= freqmin && docFreq <= freqmax) {
          // add the term to the list
          if (sort) {
            queue.add(new CountPair<>(BytesRef.deepCopyOf(term), docFreq));
          } else {

            // TODO: handle raw somehow
            if (!externalized) {
              ft.indexedToReadable(term, external);
            }
            fieldTerms.add(external.toString(), docFreq);
            i++;
          }
        }

        term = termsEnum.next();
      }

      if (sort) {
        for (CountPair<BytesRef, Integer> item : queue) {
          if (i >= limit) break;
          ft.indexedToReadable(item.key, external);
          fieldTerms.add(external.toString(), item.val);
          i++;
        }
      }
    }
  }
  @Override
  public void process(ResponseBuilder rb) throws IOException {
    SolrParams params = rb.req.getParams();
    if (params.getBool(TermsParams.TERMS, false)) {
      String lowerStr = params.get(TermsParams.TERMS_LOWER, null);
      String[] fields = params.getParams(TermsParams.TERMS_FIELD);
      if (fields != null && fields.length > 0) {
        NamedList terms = new SimpleOrderedMap();
        rb.rsp.add("terms", terms);
        int limit = params.getInt(TermsParams.TERMS_LIMIT, 10);
        if (limit < 0) {
          limit = Integer.MAX_VALUE;
        }
        String upperStr = params.get(TermsParams.TERMS_UPPER);
        boolean upperIncl = params.getBool(TermsParams.TERMS_UPPER_INCLUSIVE, false);
        boolean lowerIncl = params.getBool(TermsParams.TERMS_LOWER_INCLUSIVE, true);
        boolean sort =
            !TermsParams.TERMS_SORT_INDEX.equals(
                params.get(TermsParams.TERMS_SORT, TermsParams.TERMS_SORT_COUNT));
        int freqmin = params.getInt(TermsParams.TERMS_MINCOUNT, 1); // initialize freqmin
        int freqmax =
            params.getInt(TermsParams.TERMS_MAXCOUNT, UNLIMITED_MAX_COUNT); // initialize freqmax
        if (freqmax < 0) {
          freqmax = Integer.MAX_VALUE;
        }
        String prefix = params.get(TermsParams.TERMS_PREFIX_STR);
        String regexp = params.get(TermsParams.TERMS_REGEXP_STR);
        Pattern pattern =
            regexp != null ? Pattern.compile(regexp, resolveRegexpFlags(params)) : null;

        boolean raw = params.getBool(TermsParams.TERMS_RAW, false);
        for (int j = 0; j < fields.length; j++) {
          String field = StringHelper.intern(fields[j]);
          FieldType ft = raw ? null : rb.req.getSchema().getFieldTypeNoEx(field);
          if (ft == null) ft = new StrField();

          // If no lower bound was specified, use the prefix
          String lower = lowerStr == null ? prefix : (raw ? lowerStr : ft.toInternal(lowerStr));
          if (lower == null) lower = "";
          String upper = upperStr == null ? null : (raw ? upperStr : ft.toInternal(upperStr));

          Term lowerTerm = new Term(field, lower);
          Term upperTerm = upper == null ? null : new Term(field, upper);

          TermEnum termEnum =
              rb.req
                  .getSearcher()
                  .getReader()
                  .terms(lowerTerm); // this will be positioned ready to go
          int i = 0;
          BoundedTreeSet<CountPair<String, Integer>> queue =
              (sort ? new BoundedTreeSet<CountPair<String, Integer>>(limit) : null);
          NamedList fieldTerms = new NamedList();
          terms.add(field, fieldTerms);
          Term lowerTestTerm = termEnum.term();

          // Only advance the enum if we are excluding the lower bound and the lower Term actually
          // matches
          if (lowerTestTerm != null
              && lowerIncl == false
              && lowerTestTerm.field() == field // intern'd comparison
              && lowerTestTerm.text().equals(lower)) {
            termEnum.next();
          }

          while (i < limit || sort) {

            Term theTerm = termEnum.term();

            // check for a different field, or the end of the index.
            if (theTerm == null || field != theTerm.field()) // intern'd comparison
            break;

            String indexedText = theTerm.text();

            // stop if the prefix doesn't match
            if (prefix != null && !indexedText.startsWith(prefix)) break;

            if (pattern != null && !pattern.matcher(indexedText).matches()) {
              termEnum.next();
              continue;
            }

            if (upperTerm != null) {
              int upperCmp = theTerm.compareTo(upperTerm);
              // if we are past the upper term, or equal to it (when don't include upper) then stop.
              if (upperCmp > 0 || (upperCmp == 0 && !upperIncl)) break;
            }

            // This is a good term in the range.  Check if mincount/maxcount conditions are
            // satisfied.
            int docFreq = termEnum.docFreq();
            if (docFreq >= freqmin && docFreq <= freqmax) {
              // add the term to the list
              String label = raw ? indexedText : ft.indexedToReadable(indexedText);
              if (sort) {
                queue.add(new CountPair<String, Integer>(label, docFreq));
              } else {
                fieldTerms.add(label, docFreq);
                i++;
              }
            }

            termEnum.next();
          }

          termEnum.close();

          if (sort) {
            for (CountPair<String, Integer> item : queue) {
              if (i < limit) {
                fieldTerms.add(item.key, item.val);
                i++;
              } else {
                break;
              }
            }
          }
        }
      } else {
        throw new SolrException(
            SolrException.ErrorCode.BAD_REQUEST, "No terms.fl parameter specified");
      }
    }
  }