org.apache.lucene.search.grouping.DistinctValuesCollector Maven / Gradle / Ivy
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* 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.
*/
package org.apache.lucene.search.grouping;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import org.apache.lucene.index.LeafReaderContext;
import org.apache.lucene.search.ScoreMode;
import org.apache.lucene.search.SimpleCollector;
/**
* A second pass grouping collector that keeps track of distinct values for a specified field for the top N group.
*
* @lucene.experimental
*/
public class DistinctValuesCollector extends SecondPassGroupingCollector {
/**
* Create a DistinctValuesCollector
* @param groupSelector the group selector to determine the top-level groups
* @param groups the top-level groups to collect for
* @param valueSelector a group selector to determine which values to collect per-group
*/
public DistinctValuesCollector(GroupSelector groupSelector, Collection> groups,
GroupSelector valueSelector) {
super(groupSelector, groups, new DistinctValuesReducer<>(valueSelector));
}
private static class ValuesCollector extends SimpleCollector {
final GroupSelector valueSelector;
final Set values = new HashSet<>();
private ValuesCollector(GroupSelector valueSelector) {
this.valueSelector = valueSelector;
}
@Override
public void collect(int doc) throws IOException {
if (valueSelector.advanceTo(doc) == GroupSelector.State.ACCEPT) {
R value = valueSelector.currentValue();
if (values.contains(value) == false)
values.add(valueSelector.copyValue());
}
else {
if (values.contains(null) == false)
values.add(null);
}
}
@Override
protected void doSetNextReader(LeafReaderContext context) throws IOException {
valueSelector.setNextReader(context);
}
@Override
public ScoreMode scoreMode() {
return ScoreMode.COMPLETE_NO_SCORES;
}
}
private static class DistinctValuesReducer extends GroupReducer> {
final GroupSelector valueSelector;
private DistinctValuesReducer(GroupSelector valueSelector) {
this.valueSelector = valueSelector;
}
@Override
public boolean needsScores() {
return false;
}
@Override
protected ValuesCollector newCollector() {
return new ValuesCollector<>(valueSelector);
}
}
/**
* Returns all unique values for each top N group.
*
* @return all unique values for each top N group
*/
public List> getGroups() {
List> counts = new ArrayList<>();
for (SearchGroup group : groups) {
@SuppressWarnings("unchecked")
ValuesCollector vc = (ValuesCollector) groupReducer.getCollector(group.groupValue);
counts.add(new GroupCount<>(group.groupValue, vc.values));
}
return counts;
}
/**
* Returned by {@link DistinctValuesCollector#getGroups()},
* representing the value and set of distinct values for the group.
*/
public static class GroupCount {
public final T groupValue;
public final Set uniqueValues;
public GroupCount(T groupValue, Set values) {
this.groupValue = groupValue;
this.uniqueValues = values;
}
}
}