io.questdb.cairo.ColumnIndexerJob Maven / Gradle / Ivy
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* Copyright (c) 2014-2019 Appsicle
* Copyright (c) 2019-2020 QuestDB
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* 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
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* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
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package io.questdb.cairo;
import io.questdb.MessageBus;
import io.questdb.mp.AbstractQueueConsumerJob;
import io.questdb.mp.SOCountDownLatch;
import io.questdb.tasks.ColumnIndexerTask;
public class ColumnIndexerJob extends AbstractQueueConsumerJob {
public ColumnIndexerJob(MessageBus messageBus) {
super(messageBus.getIndexerQueue(), messageBus.getIndexerSubSequence());
}
protected boolean doRun(int workerId, 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;
}
}