content: package org.apache.lucene.search.grouping;
  
  /**
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.
   * The ASF licenses this file to You under the Apache License, Version 2.0
   * (the "License"); you may not use this file except in compliance with
   * the License.  You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  import java.io.IOException;
  import java.util.Collection;
  
  import org.apache.lucene.index.IndexReader;
  import org.apache.lucene.search.FieldCache;
  import org.apache.lucene.search.Sort;
  
  /**
   * Concrete implementation of {@link AbstractSecondPassGroupingCollector} that groups based on
   * field values and more specifically uses {@link org.apache.lucene.search.FieldCache.StringIndex}
   * to collect grouped docs.
   *
   * @lucene.experimental
   */
  public class TermSecondPassGroupingCollector extends AbstractSecondPassGroupingCollector<String> {
  
    private final SentinelIntSet ordSet;
    private FieldCache.StringIndex index;
    private final String groupField;
  
    @SuppressWarnings("unchecked")
    public TermSecondPassGroupingCollector(String groupField, Collection<SearchGroup<String>> groups, Sort groupSort, Sort withinGroupSort,
                                           int maxDocsPerGroup, boolean getScores, boolean getMaxScores, boolean fillSortFields)
        throws IOException {
      super(groups, groupSort, withinGroupSort, maxDocsPerGroup, getScores, getMaxScores, fillSortFields);
      ordSet = new SentinelIntSet(groupMap.size(), -1);
      this.groupField = groupField;
      groupDocs = (SearchGroupDocs<String>[]) new SearchGroupDocs[ordSet.keys.length];
    }
  
    @Override
    public void setNextReader(IndexReader reader, int docBase) throws IOException {
      super.setNextReader(reader, docBase);
      index = FieldCache.DEFAULT.getStringIndex(reader, groupField);
  
      // Rebuild ordSet
      ordSet.clear();
      for (SearchGroupDocs<String> group : groupMap.values()) {
  //      System.out.println("  group=" + (group.groupValue == null ? "null" : group.groupValue.utf8ToString()));
        int ord = group.groupValue == null ? 0 : index.binarySearchLookup(group.groupValue);
        if (ord >= 0) {
          groupDocs[ordSet.put(ord)] = group;
        }
      }
    }
  
    @Override
    protected SearchGroupDocs<String> retrieveGroup(int doc) throws IOException {
      int slot = ordSet.find(index.order[doc]);
      if (slot >= 0) {
        return groupDocs[slot];
      }
      return null;
    }
  }