maryannxue commented on a change in pull request #27669: [SPARK-30918][SQL]
improve the splitting of skewed partitions
URL: https://github.com/apache/spark/pull/27669#discussion_r383653912
##########
File path:
sql/core/src/main/scala/org/apache/spark/sql/execution/adaptive/OptimizeSkewedJoin.scala
##########
@@ -61,6 +85,19 @@ case class OptimizeSkewedJoin(conf: SQLConf) extends
Rule[SparkPlan] {
}
}
+ /**
+ * The goal of skew join optimization is to make the data distribution more
even. The target size
+ * to split skewed partitions is the average size of non-skewed partition,
or the
+ * target post-shuffle partition size if avg size is smaller than it.
+ */
+ private def targetSize(stats: MapOutputStatistics, medianSize: Long): Long =
{
+ val targetPostShuffleSize =
conf.getConf(SQLConf.SHUFFLE_TARGET_POSTSHUFFLE_INPUT_SIZE)
Review comment:
Why would user want the new partition size after split to be different from
the sizes of non-skew partition size? The goal of this rule is to coordinate
all partitions to be around the same size if possible...
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