solr/core/src/java/org/apache/solr/search/grouping/distributed/command/SearchGroupsFieldCommand.java

package org.apache.solr.search.grouping.distributed.command;

/*
 * 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 org.apache.lucene.search.Collector;
import org.apache.lucene.search.Sort;
import org.apache.lucene.search.grouping.SearchGroup;
import org.apache.lucene.search.grouping.TermFirstPassGroupingCollector;
import org.apache.solr.schema.SchemaField;
import org.apache.solr.search.grouping.Command;

import java.io.IOException;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.List;

/**
 *
 */
public class SearchGroupsFieldCommand implements Command<Collection<SearchGroup<String>>> {

  public static class Builder {

    private SchemaField field;
    private Sort groupSort;
    private Integer topNGroups;

    public Builder setField(SchemaField field) {
      this.field = field;
      return this;
    }

    public Builder setGroupSort(Sort groupSort) {
      this.groupSort = groupSort;
      return this;
    }

    public Builder setTopNGroups(int topNGroups) {
      this.topNGroups = topNGroups;
      return this;
    }

    public SearchGroupsFieldCommand build() {
      if (field == null || groupSort == null || topNGroups == null) {
        throw new IllegalStateException("All fields must be set");
      }

      return new SearchGroupsFieldCommand(field, groupSort, topNGroups);
    }

  }

  private final SchemaField field;
  private final Sort groupSort;
  private final int topNGroups;

  private TermFirstPassGroupingCollector firstPassGroupingCollector;

  private SearchGroupsFieldCommand(SchemaField field, Sort groupSort, int topNGroups) {
    this.field = field;
    this.groupSort = groupSort;
    this.topNGroups = topNGroups;
  }

  public List<Collector> create() throws IOException {
    if (topNGroups > 0) {
      firstPassGroupingCollector = new TermFirstPassGroupingCollector(field.getName(), groupSort, topNGroups);
      return Arrays.asList((Collector) firstPassGroupingCollector);
    } else {
      return Collections.emptyList();
    }
  }

  public Collection<SearchGroup<String>> result() {
    if (topNGroups > 0) {
      return firstPassGroupingCollector.getTopGroups(0, true);
    } else {
      return Collections.emptyList();
    }
  }

  public Sort getSortWithinGroup() {
    return null;
  }

  public Sort getGroupSort() {
    return groupSort;
  }

  public String getKey() {
    return field.getName();
  }
}