Jackie-Jiang commented on a change in pull request #6696:
URL: https://github.com/apache/incubator-pinot/pull/6696#discussion_r597350972
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File path:
pinot-core/src/main/java/org/apache/pinot/core/operator/combine/BaseCombineOperator.java
##########
@@ -50,42 +50,41 @@
private static final Logger LOGGER =
LoggerFactory.getLogger(BaseCombineOperator.class);
protected final List<Operator> _operators;
+ protected final int _numOperators;
protected final QueryContext _queryContext;
protected final ExecutorService _executorService;
protected final long _endTimeMs;
- protected final int _numOperators;
- // Use a Phaser to ensure all the Futures are done (not scheduled, finished
or interrupted) before the main thread
- // returns. We need to ensure this because the main thread holds the
reference to the segments. If a segment is
- // deleted/refreshed, the segment will be released after the main thread
returns, which would lead to undefined
- // behavior (even JVM crash) when processing queries against it.
- protected final Phaser _phaser = new Phaser(1);
- // Use a _blockingQueue to store the per-segment result
- protected final BlockingQueue<IntermediateResultsBlock> _blockingQueue;
- private final AtomicLong totalWorkerThreadCpuTimeNs = new AtomicLong(0);
- protected int _numThreads;
- protected Future[] _futures;
-
- public BaseCombineOperator(List<Operator> operators, QueryContext
queryContext, ExecutorService executorService,
- long endTimeMs) {
+ protected final int _numThreads;
+ protected final Future[] _futures;
+ // Use a _blockingQueue to store the intermediate results blocks
+ protected final BlockingQueue<IntermediateResultsBlock> _blockingQueue = new
LinkedBlockingQueue<>();
Review comment:
I considered that, but decide to use `LinkedBlockingQueue` as the
default for the following reasons:
- `ArrayBlockingQueue` pre-allocates all the memory, which might not be
needed, and has larger memory footprint
- `LinkedBlockingQueue` has better throughput because it uses separate locks
for the head and the tail
- We don't need the customized fairness policy provided by the
`ArrayBlockingQueue`
Here is the reference link:
https://stackoverflow.com/questions/35967792/when-to-prefer-linkedblockingqueue-over-arrayblockingqueue
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