org.apache.lucene.search.grouping.SearchGroup Maven / Gradle / Ivy
The newest version!
/*
* 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.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Comparator;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.NavigableSet;
import java.util.TreeSet;
import org.apache.lucene.search.FieldComparator;
import org.apache.lucene.search.Pruning;
import org.apache.lucene.search.Sort;
import org.apache.lucene.search.SortField;
/**
* Represents a group that is found during the first pass search.
*
* @lucene.experimental
*/
public class SearchGroup {
/** The value that defines this group */
public T groupValue;
/**
* The sort values used during sorting. These are the groupSort field values of the highest rank
* document (by the groupSort) within the group. Can be null if
* fillFields=false had been passed to {@link FirstPassGroupingCollector#getTopGroups}
*/
public Object[] sortValues;
@Override
public String toString() {
return ("SearchGroup(groupValue="
+ groupValue
+ " sortValues="
+ Arrays.toString(sortValues)
+ ")");
}
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
SearchGroup that = (SearchGroup) o;
if (groupValue == null) {
if (that.groupValue != null) {
return false;
}
} else if (!groupValue.equals(that.groupValue)) {
return false;
}
return true;
}
@Override
public int hashCode() {
return groupValue != null ? groupValue.hashCode() : 0;
}
private static class ShardIter {
public final Iterator> iter;
public final int shardIndex;
public ShardIter(Collection> shard, int shardIndex) {
this.shardIndex = shardIndex;
iter = shard.iterator();
assert iter.hasNext();
}
public SearchGroup next() {
assert iter.hasNext();
final SearchGroup group = iter.next();
if (group.sortValues == null) {
throw new IllegalArgumentException(
"group.sortValues is null; you must pass fillFields=true to the first pass collector");
}
return group;
}
@Override
public String toString() {
return "ShardIter(shard=" + shardIndex + ")";
}
}
// Holds all shards currently on the same group
private static class MergedGroup {
// groupValue may be null!
public final T groupValue;
public Object[] topValues;
public final List> shards = new ArrayList<>();
public int minShardIndex;
public boolean processed;
public boolean inQueue;
public MergedGroup(T groupValue) {
this.groupValue = groupValue;
}
// Only for assert
private boolean neverEquals(Object _other) {
if (_other instanceof MergedGroup) {
MergedGroup other = (MergedGroup) _other;
if (groupValue == null) {
assert other.groupValue != null;
} else {
assert !groupValue.equals(other.groupValue);
}
}
return true;
}
@Override
public boolean equals(Object _other) {
// We never have another MergedGroup instance with
// same groupValue
assert neverEquals(_other);
if (_other instanceof MergedGroup) {
MergedGroup other = (MergedGroup) _other;
if (groupValue == null) {
return other.groupValue == null;
} else {
return groupValue.equals(other.groupValue);
}
} else {
return false;
}
}
@Override
public int hashCode() {
if (groupValue == null) {
return 0;
} else {
return groupValue.hashCode();
}
}
}
private static class GroupComparator implements Comparator> {
@SuppressWarnings("rawtypes")
public final FieldComparator[] comparators;
public final int[] reversed;
@SuppressWarnings({"unchecked", "rawtypes"})
public GroupComparator(Sort groupSort) {
final SortField[] sortFields = groupSort.getSort();
comparators = new FieldComparator[sortFields.length];
reversed = new int[sortFields.length];
for (int compIDX = 0; compIDX < sortFields.length; compIDX++) {
final SortField sortField = sortFields[compIDX];
comparators[compIDX] = sortField.getComparator(1, Pruning.NONE);
reversed[compIDX] = sortField.getReverse() ? -1 : 1;
}
}
@Override
@SuppressWarnings({"unchecked", "rawtypes"})
public int compare(MergedGroup group, MergedGroup other) {
if (group == other) {
return 0;
}
// System.out.println("compare group=" + group + " other=" + other);
final Object[] groupValues = group.topValues;
final Object[] otherValues = other.topValues;
// System.out.println(" groupValues=" + groupValues + " otherValues=" + otherValues);
for (int compIDX = 0; compIDX < comparators.length; compIDX++) {
final int c =
reversed[compIDX]
* comparators[compIDX].compareValues(groupValues[compIDX], otherValues[compIDX]);
if (c != 0) {
return c;
}
}
// Tie break by min shard index:
assert group.minShardIndex != other.minShardIndex;
return group.minShardIndex - other.minShardIndex;
}
}
private static class GroupMerger {
private final GroupComparator groupComp;
private final NavigableSet> queue;
private final Map> groupsSeen;
public GroupMerger(Sort groupSort) {
groupComp = new GroupComparator<>(groupSort);
queue = new TreeSet<>(groupComp);
groupsSeen = new HashMap<>();
}
@SuppressWarnings({"unchecked", "rawtypes"})
private void updateNextGroup(int topN, ShardIter shard) {
while (shard.iter.hasNext()) {
final SearchGroup group = shard.next();
MergedGroup mergedGroup = groupsSeen.get(group.groupValue);
final boolean isNew = mergedGroup == null;
// System.out.println(" next group=" + (group.groupValue == null ? "null" : ((BytesRef)
// group.groupValue).utf8ToString()) + " sort=" + Arrays.toString(group.sortValues));
if (isNew) {
// Start a new group:
// System.out.println(" new");
mergedGroup = new MergedGroup<>(group.groupValue);
mergedGroup.minShardIndex = shard.shardIndex;
assert group.sortValues != null;
mergedGroup.topValues = group.sortValues;
groupsSeen.put(group.groupValue, mergedGroup);
mergedGroup.inQueue = true;
queue.add(mergedGroup);
} else if (mergedGroup.processed) {
// This shard produced a group that we already
// processed; move on to next group...
continue;
} else {
// System.out.println(" old");
boolean competes = false;
for (int compIDX = 0; compIDX < groupComp.comparators.length; compIDX++) {
final int cmp =
groupComp.reversed[compIDX]
* groupComp.comparators[compIDX].compareValues(
group.sortValues[compIDX], mergedGroup.topValues[compIDX]);
if (cmp < 0) {
// Definitely competes
competes = true;
break;
} else if (cmp > 0) {
// Definitely does not compete
break;
} else if (compIDX == groupComp.comparators.length - 1) {
if (shard.shardIndex < mergedGroup.minShardIndex) {
competes = true;
}
}
}
// System.out.println(" competes=" + competes);
if (competes) {
// Group's sort changed -- remove & re-insert
if (mergedGroup.inQueue) {
queue.remove(mergedGroup);
}
mergedGroup.topValues = group.sortValues;
mergedGroup.minShardIndex = shard.shardIndex;
queue.add(mergedGroup);
mergedGroup.inQueue = true;
}
}
mergedGroup.shards.add(shard);
break;
}
// Prune un-competitive groups:
while (queue.size() > topN) {
final MergedGroup group = queue.pollLast();
// System.out.println("PRUNE: " + group);
group.inQueue = false;
}
}
public Collection> merge(
List>> shards, int offset, int topN) {
final int maxQueueSize = offset + topN;
// System.out.println("merge");
// Init queue:
for (int shardIDX = 0; shardIDX < shards.size(); shardIDX++) {
final Collection> shard = shards.get(shardIDX);
if (!shard.isEmpty()) {
// System.out.println(" insert shard=" + shardIDX);
updateNextGroup(maxQueueSize, new ShardIter<>(shard, shardIDX));
}
}
// Pull merged topN groups:
final List> newTopGroups = new ArrayList<>(topN);
int count = 0;
while (!queue.isEmpty()) {
final MergedGroup group = queue.pollFirst();
group.processed = true;
// System.out.println(" pop: shards=" + group.shards + " group=" + (group.groupValue ==
// null ? "null" : (((BytesRef) group.groupValue).utf8ToString())) + " sortValues=" +
// Arrays.toString(group.topValues));
if (count++ >= offset) {
final SearchGroup newGroup = new SearchGroup<>();
newGroup.groupValue = group.groupValue;
newGroup.sortValues = group.topValues;
newTopGroups.add(newGroup);
if (newTopGroups.size() == topN) {
break;
}
// } else {
// System.out.println(" skip < offset");
}
// Advance all iters in this group:
for (ShardIter shardIter : group.shards) {
updateNextGroup(maxQueueSize, shardIter);
}
}
if (newTopGroups.isEmpty()) {
return null;
} else {
return newTopGroups;
}
}
}
/**
* Merges multiple collections of top groups, for example obtained from separate index shards. The
* provided groupSort must match how the groups were sorted, and the provided SearchGroups must
* have been computed with fillFields=true passed to {@link
* FirstPassGroupingCollector#getTopGroups}.
*
* NOTE: this returns null if the topGroups is empty.
*/
public static Collection> merge(
List>> topGroups, int offset, int topN, Sort groupSort) {
if (topGroups.isEmpty()) {
return null;
} else {
return new GroupMerger(groupSort).merge(topGroups, offset, topN);
}
}
}