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Core Hazelcast Module
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/*
 * Copyright (c) 2008-2020, Hazelcast, Inc. All Rights Reserved.
 *
 * Licensed 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 com.hazelcast.map.impl.query;

import com.hazelcast.internal.iteration.IterationPointer;
import com.hazelcast.internal.util.executor.ManagedExecutorService;
import com.hazelcast.query.Predicate;
import com.hazelcast.query.impl.QueryableEntriesSegment;
import com.hazelcast.query.impl.predicates.PagingPredicateImpl;

import java.util.ArrayList;
import java.util.Collection;
import java.util.List;
import java.util.Map;
import java.util.concurrent.Callable;
import java.util.concurrent.Future;

import static com.hazelcast.internal.util.FutureUtil.RETHROW_EVERYTHING;
import static com.hazelcast.internal.util.FutureUtil.returnWithDeadline;
import static com.hazelcast.internal.util.SetUtil.singletonPartitionIdSet;
import static java.util.concurrent.TimeUnit.MILLISECONDS;

/**
 * Implementation of the {@link PartitionScanExecutor} which executes the partition scan in a parallel-fashion
 * delegating to the underlying executor.
 */
public class ParallelPartitionScanExecutor implements PartitionScanExecutor {

    private final PartitionScanRunner partitionScanRunner;
    private final ManagedExecutorService executor;
    private final int timeoutInMillis;

    public ParallelPartitionScanExecutor(PartitionScanRunner partitionScanRunner,
                                         ManagedExecutorService executor,
                                         int timeoutInMillis) {
        this.partitionScanRunner = partitionScanRunner;
        this.executor = executor;
        this.timeoutInMillis = timeoutInMillis;
    }

    @SuppressWarnings("unchecked")
    @Override
    public void execute(String mapName, Predicate predicate, Collection partitions, Result result) {
        runUsingPartitionScanWithoutPaging(mapName, predicate, partitions, result);
        if (predicate instanceof PagingPredicateImpl) {
            PagingPredicateImpl pagingPredicate = (PagingPredicateImpl) predicate;
            Map.Entry nearestAnchorEntry = pagingPredicate.getNearestAnchorEntry();
            result.orderAndLimit(pagingPredicate, nearestAnchorEntry);
        }
    }

    /**
     * {@inheritDoc}
     * Parallel execution for a partition chunk query is not supported.
     */
    @Override
    public QueryableEntriesSegment execute(
            String mapName, Predicate predicate, int partitionId,
            IterationPointer[] pointers, int fetchSize) {
        return partitionScanRunner.run(mapName, predicate, partitionId, pointers, fetchSize);
    }

    protected void runUsingPartitionScanWithoutPaging(String name, Predicate predicate, Collection partitions,
                                                      Result result) {
        List> futures = new ArrayList<>(partitions.size());

        for (Integer partitionId : partitions) {
            Future future = runPartitionScanForPartition(name, predicate, partitionId, result.createSubResult());
            futures.add(future);
        }

        Collection subResults = waitForResult(futures, timeoutInMillis);
        for (Result subResult : subResults) {
            result.combine(subResult);
        }
    }

    protected Future runPartitionScanForPartition(String name, Predicate predicate, int partitionId, Result result) {
        QueryPartitionCallable task = new QueryPartitionCallable(name, predicate, partitionId, result);
        return executor.submit(task);
    }

    private static Collection waitForResult(List> lsFutures, int timeoutInMillis) {
        return returnWithDeadline(lsFutures, timeoutInMillis, MILLISECONDS, RETHROW_EVERYTHING);
    }

    private final class QueryPartitionCallable implements Callable {
        protected final int partition;
        protected final String name;
        protected final Predicate predicate;
        protected final Result result;

        private QueryPartitionCallable(String name, Predicate predicate, int partitionId, Result result) {
            this.name = name;
            this.predicate = predicate;
            this.partition = partitionId;
            this.result = result;
        }

        @Override
        public Result call() {
            partitionScanRunner.run(name, predicate, partition, result);
            result.setPartitionIds(singletonPartitionIdSet(partitionScanRunner.partitionService.getPartitionCount(),
                    partition));
            return result;
        }
    }
}