org.apache.lucene.search.grouping.SecondPassGroupingCollector.java Source code

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Here is the source code for org.apache.lucene.search.grouping.SecondPassGroupingCollector.java

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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.Objects;

import org.apache.lucene.index.LeafReaderContext;
import org.apache.lucene.search.Scorable;
import org.apache.lucene.search.ScoreMode;
import org.apache.lucene.search.SimpleCollector;

/**
 * SecondPassGroupingCollector runs over an already collected set of
 * groups, further applying a {@link GroupReducer} to each group
 *
 * @see TopGroupsCollector
 * @see DistinctValuesCollector
 *
 * @lucene.experimental
 */
public class SecondPassGroupingCollector<T> extends SimpleCollector {

    protected final GroupSelector<T> groupSelector;
    protected final Collection<SearchGroup<T>> groups;
    protected final GroupReducer<T, ?> groupReducer;

    protected int totalHitCount;
    protected int totalGroupedHitCount;

    /**
     * Create a new SecondPassGroupingCollector
     * @param groupSelector   the GroupSelector that defines groups for this search
     * @param groups          the groups to collect documents for
     * @param reducer         the reducer to apply to each group
     */
    public SecondPassGroupingCollector(GroupSelector<T> groupSelector, Collection<SearchGroup<T>> groups,
            GroupReducer<T, ?> reducer) {

        //System.out.println("SP init");
        if (groups.isEmpty()) {
            throw new IllegalArgumentException("no groups to collect (groups is empty)");
        }

        this.groupSelector = Objects.requireNonNull(groupSelector);
        this.groupSelector.setGroups(groups);

        this.groups = Objects.requireNonNull(groups);
        this.groupReducer = reducer;
        reducer.setGroups(groups);
    }

    /**
     * @return the GroupSelector used in this collector
     */
    public GroupSelector<T> getGroupSelector() {
        return groupSelector;
    }

    @Override
    public ScoreMode scoreMode() {
        return groupReducer.needsScores() ? ScoreMode.COMPLETE : ScoreMode.COMPLETE_NO_SCORES;
    }

    @Override
    public void setScorer(Scorable scorer) throws IOException {
        groupReducer.setScorer(scorer);
    }

    @Override
    public void collect(int doc) throws IOException {
        totalHitCount++;
        if (groupSelector.advanceTo(doc) == GroupSelector.State.SKIP)
            return;
        totalGroupedHitCount++;
        T value = groupSelector.currentValue();
        groupReducer.collect(value, doc);
    }

    @Override
    protected void doSetNextReader(LeafReaderContext readerContext) throws IOException {
        groupReducer.setNextReader(readerContext);
        groupSelector.setNextReader(readerContext);
    }

}