io.questdb.cairo.ColumnIndexerJob Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of core Show documentation
QuestDB is High Performance Time Series Database
The newest version!
/*******************************************************************************
 *     ___                  _   ____  ____
 *    / _ \ _   _  ___  ___| |_|  _ \| __ )
 *   | | | | | | |/ _ \/ __| __| | | |  _ \
 *   | |_| | |_| |  __/\__ \ |_| |_| | |_) |
 *    \__\_\\__,_|\___||___/\__|____/|____/
 *
 *  Copyright (c) 2014-2019 Appsicle
 *  Copyright (c) 2019-2020 QuestDB
 *
 *  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 io.questdb.cairo;

import io.questdb.MessageBus;
import io.questdb.mp.Job;
import io.questdb.mp.RingQueue;
import io.questdb.mp.SOCountDownLatch;
import io.questdb.mp.Sequence;
import io.questdb.tasks.ColumnIndexerTask;

public class ColumnIndexerJob implements Job {
    private final RingQueue queue;
    private final Sequence subSeq;

    public ColumnIndexerJob(MessageBus messageBus) {
        this.queue = messageBus.getIndexerQueue();
        this.subSeq = messageBus.getIndexerSubSequence();
    }

    @Override
    public boolean run(int workerId) {
        long cursor = subSeq.next();
        return cursor > -1 && doIndex(cursor);
    }

    private boolean doIndex(long cursor) {
        final ColumnIndexerTask queueItem = queue.get(cursor);
        // copy values and release queue item
        final ColumnIndexer indexer = queueItem.indexer;
        final long lo = queueItem.lo;
        final long hi = queueItem.hi;
        final long indexSequence = queueItem.sequence;
        final SOCountDownLatch latch = queueItem.countDownLatch;
        subSeq.done(cursor);

        // On the face of it main thread could have consumed same sequence as
        // child workers. The reason it is undesirable is because all writers
        // share the same queue and main thread end up indexing content for other writers.
        // Using CAS allows main thread to steal only parts of its own job.
        if (indexer.tryLock(indexSequence)) {
            TableWriter.indexAndCountDown(indexer, lo, hi, latch);
            return true;
        }
        // This is hard to test. Condition occurs when main thread successfully steals
        // work from under nose of this worker.
        return false;
    }
}