cloud-fan commented on a change in pull request #28123:
URL: https://github.com/apache/spark/pull/28123#discussion_r433262285
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File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/internal/SQLConf.scala
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@@ -2586,6 +2586,26 @@ object SQLConf {
.checkValue(_ > 0, "The timeout value must be positive")
.createWithDefault(10L)
+ val COALESCE_BUCKETS_IN_SORT_MERGE_JOIN_ENABLED =
+ buildConf("spark.sql.bucketing.coalesceBucketsInSortMergeJoin.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.")
+ .version("3.1.0")
+ .booleanConf
+ .createWithDefault(false)
+
+ val COALESCE_BUCKETS_IN_SORT_MERGE_JOIN_MAX_NUM_BUCKETS_DIFF =
+
buildConf("spark.sql.bucketing.coalesceBucketsInSortMergeJoin.maxNumBucketsDiff")
+ .doc("The difference in count of two buckets being coalesced should be
less than or " +
Review comment:
shall we use the ration not the absolute difference? e.g. coalesce 128
buckets to 1 looks not good. Maybe we can say: we can coalesce the buckets to
at most n times slower.
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