loquisgon commented on code in PR #12443:
URL: https://github.com/apache/druid/pull/12443#discussion_r870639690
##########
indexing-service/src/main/java/org/apache/druid/indexing/common/task/batch/parallel/ParallelIndexSupervisorTask.java:
##########
@@ -901,13 +906,43 @@ public static Map<Interval, Integer>
determineNumShardsFromCardinalityReport(
{
// aggregate all the sub-reports
Map<Interval, Union> finalCollectors = mergeCardinalityReports(reports);
+ return computeIntervalToNumShards(maxRowsPerSegment, finalCollectors);
+ }
+ @Nonnull
+ @VisibleForTesting
+ static Map<Interval, Integer> computeIntervalToNumShards(
+ int maxRowsPerSegment,
+ Map<Interval, Union> finalCollectors
+ )
+ {
return CollectionUtils.mapValues(
finalCollectors,
union -> {
final double estimatedCardinality = union.getEstimate();
- // determine numShards based on maxRowsPerSegment and the cardinality
- final long estimatedNumShards = Math.round(estimatedCardinality /
maxRowsPerSegment);
+ final long estimatedNumShards;
+ if (estimatedCardinality <= 0) {
+ // I don't think we can use the estimate in any way being
negative, seven sounds like a nice prime number
+ // it is ok if we end up not filling them all, the ingestion code
handles that
+ // Seven on the other hand will at least create some shards rather
than potentially a single huge one
+ estimatedNumShards = 7L;
+ LOG.warn("Estimated cardinality for union of estimates is zero or
less: %.2f, setting num shards to %d",
+ estimatedCardinality, estimatedNumShards
+ );
+ } else {
+ // determine numShards based on maxRowsPerSegment and the
cardinality
+ estimatedNumShards = Math.round(estimatedCardinality /
maxRowsPerSegment);
+ }
+ LOG.debug("estimatedNumShards %d given estimated cardinality %.2f
and maxRowsPerSegment %d",
Review Comment:
How many depends on how many shards were created per interval. This code
will. union all the independent shards created from the parallel sub-tasks in
order to create the final shard. I am being cautious again because before such
logging was considered excessive.
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