jihoonson commented on a change in pull request #6629: Add support parallel
combine in brokers
URL: https://github.com/apache/incubator-druid/pull/6629#discussion_r243026558
##########
File path: processing/src/main/java/org/apache/druid/query/QueryContexts.java
##########
@@ -174,6 +179,35 @@
}
}
+ private static int checkPositive(String propertyName, int val)
+ {
+ Preconditions.checkArgument(
+ val > 0,
+ "%s should be positive, but [%s]",
+ propertyName,
+ val
+ );
+ return val;
+ }
+
+ /**
+ * Return the configured number of combine threads if any. Others {@link
#NO_PARALLEL_COMBINE_THREADS}.
+ */
+ public static <T> int getNumBrokerParallelCombineThreads(Query<T> query)
+ {
+ return parseInt(query, NUM_BROKER_PARALLEL_COMBINE_THREADS,
NO_PARALLEL_COMBINE_THREADS);
Review comment:
@leventov got it. I think now I understand what you mean though it's still
not clear how to reserve the threads needed for hierarchical merge with
forkJoinPool. (If hierarchical merge is done as in this PR, it needs sort of a
gang scheduling. Once we decide to use some threads for a query, they should be
available at the same time.)
Anyway, I like this idea and will change my implementation. Probably will
close this and raise another PR. Thanks.
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