jihoonson commented on a change in pull request #9448: Fix superbatch merge
last partition boundaries
URL: https://github.com/apache/druid/pull/9448#discussion_r387318051
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File path:
indexing-service/src/main/java/org/apache/druid/indexing/common/task/batch/parallel/ParallelIndexSupervisorTask.java
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@@ -760,29 +761,39 @@ private PartitionBoundaries
determineRangePartition(Collection<StringDistributio
// See PartitionStat in GeneratedPartitionsReport.
final List<Pair<Interval, Integer>> partitions = new
ArrayList<>(partitionToLocations.keySet());
Collections.shuffle(partitions, ThreadLocalRandom.current());
- final int numPartitionsPerTask = (int) Math.round(partitions.size() /
(double) numMergeTasks);
final List<M> assignedPartitionLocations = new ArrayList<>(numMergeTasks);
- for (int i = 0; i < numMergeTasks - 1; i++) {
+ for (int i = 0; i < numMergeTasks; i++) {
+ Pair<Integer, Integer> partitionBoundaries = getPartitionBoundaries(i,
partitions.size(), numMergeTasks);
final List<L> assignedToSameTask = partitions
- .subList(i * numPartitionsPerTask, (i + 1) * numPartitionsPerTask)
+ .subList(partitionBoundaries.lhs, partitionBoundaries.rhs)
.stream()
.flatMap(intervalAndPartitionId ->
partitionToLocations.get(intervalAndPartitionId).stream())
.collect(Collectors.toList());
assignedPartitionLocations.add(createPartialSegmentMergeIOConfig.apply(assignedToSameTask));
}
- // The last task is assigned all remaining partitions.
- final List<L> assignedToSameTask = partitions
- .subList((numMergeTasks - 1) * numPartitionsPerTask, partitions.size())
- .stream()
- .flatMap(intervalAndPartitionId ->
partitionToLocations.get(intervalAndPartitionId).stream())
- .collect(Collectors.toList());
-
assignedPartitionLocations.add(createPartialSegmentMergeIOConfig.apply(assignedToSameTask));
-
return assignedPartitionLocations;
}
+ /**
+ * Partition items into as evenly-sized splits as possible.
+ *
+ * @param index index of partition
+ * @param total number of items to partitions
+ * @param splits number of desired partitions
+ *
+ * @return partition range: [lhs, rhs)
+ */
+ private static Pair<Integer, Integer> getPartitionBoundaries(int index, int
total, int splits)
+ {
+ int chunk = total / splits;
+ int remainder = total % splits;
+ int start = index * chunk + (index < remainder ? index : remainder);
Review comment:
I think the comment would be nice.
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