org.apache.lucene.search.grouping.GroupReducer 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.Collection;
import java.util.HashMap;
import java.util.Map;
import org.apache.lucene.index.LeafReaderContext;
import org.apache.lucene.search.Collector;
import org.apache.lucene.search.LeafCollector;
import org.apache.lucene.search.Scorable;
/**
* Concrete implementations of this class define what to collect for individual groups during the
* second-pass of a grouping search.
*
* Each group is assigned a Collector returned by {@link #newCollector()}, and {@link
* LeafCollector#collect(int)} is called for each document that is in a group
*
* @see SecondPassGroupingCollector
* @param the type of the value used for grouping
* @param the type of {@link Collector} used to reduce each group
*/
public abstract class GroupReducer {
private final Map> groups = new HashMap<>();
/**
* Define which groups should be reduced.
*
* Called by {@link SecondPassGroupingCollector}
*/
public void setGroups(Collection> groups) {
for (SearchGroup group : groups) {
this.groups.put(group.groupValue, new GroupCollector<>(newCollector()));
}
}
/** Whether or not this reducer requires collected documents to be scored */
public abstract boolean needsScores();
/** Creates a new Collector for each group */
protected abstract C newCollector();
/** Get the Collector for a given group */
public final C getCollector(T value) {
return groups.get(value).collector;
}
/**
* Collect a given document into a given group
*
* @throws IOException on error
*/
public final void collect(T value, int doc) throws IOException {
GroupCollector collector = groups.get(value);
collector.leafCollector.collect(doc);
}
/** Set the Scorer on all group collectors */
public final void setScorer(Scorable scorer) throws IOException {
for (GroupCollector collector : groups.values()) {
collector.leafCollector.setScorer(scorer);
}
}
/** Called when the parent {@link SecondPassGroupingCollector} moves to a new segment */
public final void setNextReader(LeafReaderContext ctx) throws IOException {
for (GroupCollector collector : groups.values()) {
collector.leafCollector = collector.collector.getLeafCollector(ctx);
}
}
private static final class GroupCollector {
final C collector;
LeafCollector leafCollector;
private GroupCollector(C collector) {
this.collector = collector;
}
}
}