private void handleFilterExclusions() throws IOException {
    List<String> excludeTags = freq.domain.excludeTags;

    if (excludeTags == null || excludeTags.size() == 0) {
      return;
    }

    // TODO: somehow remove responsebuilder dependency
    ResponseBuilder rb = SolrRequestInfo.getRequestInfo().getResponseBuilder();
    Map tagMap = (Map) rb.req.getContext().get("tags");
    if (tagMap == null) {
      // no filters were tagged
      return;
    }

    IdentityHashMap<Query, Boolean> excludeSet = new IdentityHashMap<>();
    for (String excludeTag : excludeTags) {
      Object olst = tagMap.get(excludeTag);
      // tagMap has entries of List<String,List<QParser>>, but subject to change in the future
      if (!(olst instanceof Collection)) continue;
      for (Object o : (Collection<?>) olst) {
        if (!(o instanceof QParser)) continue;
        QParser qp = (QParser) o;
        try {
          excludeSet.put(qp.getQuery(), Boolean.TRUE);
        } catch (SyntaxError syntaxError) {
          // This should not happen since we should only be retrieving a previously parsed query
          throw new SolrException(SolrException.ErrorCode.BAD_REQUEST, syntaxError);
        }
      }
    }
    if (excludeSet.size() == 0) return;

    List<Query> qlist = new ArrayList<>();

    // add the base query
    if (!excludeSet.containsKey(rb.getQuery())) {
      qlist.add(rb.getQuery());
    }

    // add the filters
    if (rb.getFilters() != null) {
      for (Query q : rb.getFilters()) {
        if (!excludeSet.containsKey(q)) {
          qlist.add(q);
        }
      }
    }

    // now walk back up the context tree
    // TODO: we lose parent exclusions...
    for (FacetContext curr = fcontext; curr != null; curr = curr.parent) {
      if (curr.filter != null) {
        qlist.add(curr.filter);
      }
    }

    // recompute the base domain
    fcontext.base = fcontext.searcher.getDocSet(qlist);
  }
  protected DocSet computeDocSet(DocSet baseDocSet, List<String> excludeTagList)
      throws SyntaxError, IOException {
    Map<?, ?> tagMap = (Map<?, ?>) req.getContext().get("tags");
    // rb can be null if facets are being calculated from a RequestHandler e.g. MoreLikeThisHandler
    if (tagMap == null || rb == null) {
      return baseDocSet;
    }

    IdentityHashMap<Query, Boolean> excludeSet = new IdentityHashMap<>();
    for (String excludeTag : excludeTagList) {
      Object olst = tagMap.get(excludeTag);
      // tagMap has entries of List<String,List<QParser>>, but subject to change in the future
      if (!(olst instanceof Collection)) continue;
      for (Object o : (Collection<?>) olst) {
        if (!(o instanceof QParser)) continue;
        QParser qp = (QParser) o;
        excludeSet.put(qp.getQuery(), Boolean.TRUE);
      }
    }
    if (excludeSet.size() == 0) return baseDocSet;

    List<Query> qlist = new ArrayList<>();

    // add the base query
    if (!excludeSet.containsKey(rb.getQuery())) {
      qlist.add(rb.getQuery());
    }

    // add the filters
    if (rb.getFilters() != null) {
      for (Query q : rb.getFilters()) {
        if (!excludeSet.containsKey(q)) {
          qlist.add(q);
        }
      }
    }

    // get the new base docset for this facet
    DocSet base = searcher.getDocSet(qlist);
    if (rb.grouping() && rb.getGroupingSpec().isTruncateGroups()) {
      Grouping grouping = new Grouping(searcher, null, rb.getQueryCommand(), false, 0, false);
      grouping.setWithinGroupSort(rb.getGroupingSpec().getSortWithinGroup());
      if (rb.getGroupingSpec().getFields().length > 0) {
        grouping.addFieldCommand(rb.getGroupingSpec().getFields()[0], req);
      } else if (rb.getGroupingSpec().getFunctions().length > 0) {
        grouping.addFunctionCommand(rb.getGroupingSpec().getFunctions()[0], req);
      } else {
        return base;
      }
      AbstractAllGroupHeadsCollector allGroupHeadsCollector =
          grouping.getCommands().get(0).createAllGroupCollector();
      searcher.search(base.getTopFilter(), allGroupHeadsCollector);
      return new BitDocSet(allGroupHeadsCollector.retrieveGroupHeads(searcher.maxDoc()));
    } else {
      return base;
    }
  }