jihoonson commented on a change in pull request #5913: Move Caching Cluster
Client to java streams and allow parallel intermediate merges
URL: https://github.com/apache/incubator-druid/pull/5913#discussion_r214210501
##########
File path: server/src/main/java/io/druid/client/CachingClusteredClient.java
##########
@@ -162,34 +184,75 @@ public CachingClusteredClient(
return new SpecificQueryRunnable<>(queryPlus,
responseContext).run(timelineConverter);
}
- @Override
- public <T> QueryRunner<T> getQueryRunnerForSegments(final Query<T> query,
final Iterable<SegmentDescriptor> specs)
+ private <T> QueryRunner<T> runAndMergeWithTimelineChange(
+ final Query<T> query,
+ final UnaryOperator<TimelineLookup<String, ServerSelector>>
timelineConverter
+ )
{
- return new QueryRunner<T>()
- {
- @Override
- public Sequence<T> run(final QueryPlus<T> queryPlus, final Map<String,
Object> responseContext)
- {
- return CachingClusteredClient.this.run(
+ final OptionalLong mergeBatch =
QueryContexts.getIntermediateMergeBatchThreshold(query);
+
+ if (mergeBatch.isPresent()) {
+ final QueryRunnerFactory<T, Query<T>> queryRunnerFactory =
conglomerate.findFactory(query);
+ final QueryToolChest<T, Query<T>> toolChest =
queryRunnerFactory.getToolchest();
+ return (queryPlus, responseContext) -> {
+ final Stream<? extends Sequence<T>> sequences = run(
queryPlus,
responseContext,
- timeline -> {
- final VersionedIntervalTimeline<String, ServerSelector>
timeline2 =
- new VersionedIntervalTimeline<>(Ordering.natural());
- for (SegmentDescriptor spec : specs) {
- final PartitionHolder<ServerSelector> entry =
timeline.findEntry(spec.getInterval(), spec.getVersion());
- if (entry != null) {
- final PartitionChunk<ServerSelector> chunk =
entry.getChunk(spec.getPartitionNumber());
- if (chunk != null) {
- timeline2.add(spec.getInterval(), spec.getVersion(),
chunk);
- }
- }
- }
- return timeline2;
- }
+ timelineConverter
+ );
+ return MergeWorkTask.parallelMerge(
+ sequences.parallel(),
+ sequenceStream ->
+ new FluentQueryRunnerBuilder<>(toolChest)
+ .create(
+ queryRunnerFactory.mergeRunners(
Review comment:
@drcrallen thanks, but some of my comments are not addressed. Some queries
don't use `ChainedExecutionQueryRunner`. The groupBy query is an example.
groupBy v1 and groupBy v2 use `GroupByMergedQueryRunner.run()` and
`GroupByMergingQueryRunnerV2.run()` in `QueryRunnerFactory.mergeRunners`,
respectively. And they also have some blocking mechanism which requires to be
wrapped by `ForkJoinPool.managedBlock()`. For example, there are two places in
`GroupByMergingQueryRunnerV2.run()`. One is to [get
mergeBuffers](https://github.com/apache/incubator-druid/blob/master/processing/src/main/java/org/apache/druid/query/groupby/epinephelinae/GroupByMergingQueryRunnerV2.java#L336-L340)
and another is to [wait for futures to
complete](https://github.com/apache/incubator-druid/blob/master/processing/src/main/java/org/apache/druid/query/groupby/epinephelinae/GroupByMergingQueryRunnerV2.java#L365).
All these places should be handled properly.
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