viirya commented on a change in pull request #29079:
URL: https://github.com/apache/spark/pull/29079#discussion_r456839808
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File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/internal/SQLConf.scala
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@@ -2651,12 +2651,13 @@ object SQLConf {
.booleanConf
.createWithDefault(true)
- val COALESCE_BUCKETS_IN_SORT_MERGE_JOIN_ENABLED =
- buildConf("spark.sql.bucketing.coalesceBucketsInSortMergeJoin.enabled")
+ val COALESCE_BUCKETS_IN_JOIN_ENABLED =
+ buildConf("spark.sql.bucketing.coalesceBucketsInJoin.enabled")
.doc("When true, if two bucketed tables with the different number of
buckets are joined, " +
"the side with a bigger number of buckets will be coalesced to have
the same number " +
- "of buckets as the other side. Bucket coalescing is applied only to
sort-merge joins " +
- "and only when the bigger number of buckets is divisible by the
smaller number of buckets.")
+ "of buckets as the other side. Bigger number of buckets is divisible
by the smaller " +
+ "number of buckets. Bucket coalescing is applied to sort-merge joins
and " +
+ "shuffled hash join.")
Review comment:
Can we add more doc like "Coalescing bucketed table can avoid
unnecessary shuffling during joining but it also reduces parallelism and could
possibly cause OOM for shuffled hash join"?
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