org.apache.solr.search.EarlyTerminatingSortingCollector.java Source code

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Here is the source code for org.apache.solr.search.EarlyTerminatingSortingCollector.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.solr.search;

import java.io.IOException;
import java.util.Arrays;
import java.util.concurrent.atomic.AtomicBoolean;

import org.apache.lucene.index.IndexWriterConfig;
import org.apache.lucene.index.LeafReaderContext;
import org.apache.lucene.search.CollectionTerminatedException;
import org.apache.lucene.search.Collector;
import org.apache.lucene.search.FilterCollector;
import org.apache.lucene.search.FilterLeafCollector;
import org.apache.lucene.search.LeafCollector;
import org.apache.lucene.search.Sort;
import org.apache.lucene.search.SortField;
import org.apache.lucene.search.TopDocsCollector;
import org.apache.lucene.search.TopFieldCollector;
import org.apache.lucene.search.TotalHitCountCollector;

/**
 * A {@link Collector} that early terminates collection of documents on a
 * per-segment basis, if the segment was sorted according to the given
 * {@link Sort}.
 *
 * <p>
 * <b>NOTE:</b> the {@code Collector} detects segments sorted according to a
 * an {@link IndexWriterConfig#setIndexSort}. Also, it collects up to a specified
 * {@code numDocsToCollect} from each segment, and therefore is mostly suitable
 * for use in conjunction with collectors such as {@link TopDocsCollector}, and
 * not e.g. {@link TotalHitCountCollector}.
 * <p>
 * <b>NOTE</b>: If you wrap a {@code TopDocsCollector} that sorts in the same
 * order as the index order, the returned {@link TopDocsCollector#topDocs() TopDocs}
 * will be correct. However the total of {@link TopDocsCollector#getTotalHits()
 * hit count} will be vastly underestimated since not all matching documents will have
 * been collected.
 *
 * @deprecated Use {@link TopFieldCollector} and set trackTotalHits to false.
 * @lucene.experimental
 */
@Deprecated
final class EarlyTerminatingSortingCollector extends FilterCollector {

    /** Returns whether collection can be early-terminated if it sorts with the
     *  provided {@link Sort} and if segments are merged with the provided
     *  {@link Sort}. */
    public static boolean canEarlyTerminate(Sort searchSort, Sort mergePolicySort) {
        final SortField[] fields1 = searchSort.getSort();
        final SortField[] fields2 = mergePolicySort.getSort();
        // early termination is possible if fields1 is a prefix of fields2
        if (fields1.length > fields2.length) {
            return false;
        }
        return Arrays.asList(fields1).equals(Arrays.asList(fields2).subList(0, fields1.length));
    }

    /** Sort used to sort the search results */
    protected final Sort sort;
    /** Number of documents to collect in each segment */
    protected final int numDocsToCollect;
    private final AtomicBoolean terminatedEarly = new AtomicBoolean(false);

    /**
     * Create a new {@link EarlyTerminatingSortingCollector} instance.
     *
     * @param in
     *          the collector to wrap
     * @param sort
     *          the sort you are sorting the search results on
     * @param numDocsToCollect
     *          the number of documents to collect on each segment. When wrapping
     *          a {@link TopDocsCollector}, this number should be the number of
     *          hits.
     * @throws IllegalArgumentException if the sort order doesn't allow for early
     *          termination with the given merge policy.
     */
    public EarlyTerminatingSortingCollector(Collector in, Sort sort, int numDocsToCollect) {
        super(in);
        if (numDocsToCollect <= 0) {
            throw new IllegalArgumentException("numDocsToCollect must always be > 0, got " + numDocsToCollect);
        }
        this.sort = sort;
        this.numDocsToCollect = numDocsToCollect;
    }

    @Override
    public LeafCollector getLeafCollector(LeafReaderContext context) throws IOException {
        Sort segmentSort = context.reader().getMetaData().getSort();
        if (segmentSort != null && canEarlyTerminate(sort, segmentSort) == false) {
            throw new IllegalStateException("Cannot early terminate with sort order " + sort
                    + " if segments are sorted with " + segmentSort);
        }

        if (segmentSort != null) {
            // segment is sorted, can early-terminate
            return new FilterLeafCollector(super.getLeafCollector(context)) {
                private int numCollected;

                @Override
                public void collect(int doc) throws IOException {
                    super.collect(doc);
                    if (++numCollected >= numDocsToCollect) {
                        terminatedEarly.set(true);
                        throw new CollectionTerminatedException();
                    }
                }

            };
        } else {
            return super.getLeafCollector(context);
        }
    }

    public boolean terminatedEarly() {
        return terminatedEarly.get();
    }
}