AMashenkov commented on a change in pull request #9081: URL: https://github.com/apache/ignite/pull/9081#discussion_r642428288
########## File path: modules/core/src/main/java/org/apache/ignite/internal/processors/cache/query/MergeSortDistributedCacheQueryReducer.java ########## @@ -0,0 +1,298 @@ +/* + * 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.ignite.internal.processors.cache.query; + +import java.lang.reflect.Array; +import java.util.ArrayList; +import java.util.Arrays; +import java.util.Collection; +import java.util.Comparator; +import java.util.List; +import java.util.Map; +import java.util.NoSuchElementException; +import java.util.UUID; +import java.util.concurrent.ConcurrentHashMap; +import org.apache.ignite.IgniteCheckedException; +import org.apache.ignite.cluster.ClusterNode; +import org.apache.ignite.internal.util.typedef.internal.U; +import org.jetbrains.annotations.Nullable; + +/** + * Reducer of distirbuted query that sort result through all nodes. Note that it's assumed that every node + * returns pre-sorted collection of data. + */ +public class MergeSortDistributedCacheQueryReducer<R> extends UnsortedDistributedCacheQueryReducer<R> { + /** Map of Node ID to stream. Used for inserting new pages. */ + private final Map<UUID, NodePageStream> streamsMap; + + /** Array of streams. Used for iteration over result pages. */ + private final NodePageStream[] streams; + + /** If {@code true} then there wasn't call {@link #hasNext()} on this reducer. */ + private boolean first = true; + + /** + * Offset of current stream to get next value. This offset only increments if a stream is done. The array {@link + * #streams} is sorted to put stream with lowest value on this offset. + */ + private int streamOff; + + /** Compares head of streams to get lowest value at the moment. */ + private final Comparator<NodePageStream> streamCmp; + + /** + * @param rowCmp Comparator to sort query results from different nodes. + */ + public MergeSortDistributedCacheQueryReducer(GridCacheQueryFutureAdapter fut, long reqId, + CacheQueryPageRequester fetcher, Collection<ClusterNode> nodes, Comparator<R> rowCmp + ) { + super(fut, reqId, fetcher, nodes); + + synchronized (queueLock()) { Review comment: Why we need any synchronization here? No statements have any side effects. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org
