[GitHub] [kylin] zzcclp commented on a change in pull request #1618: KYLIN-4945 Repartition encoded dataset to avoid data skew caused by a single column

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zzcclp commented on a change in pull request #1618:
URL: https://github.com/apache/kylin/pull/1618#discussion_r607579269



##########
File path: kylin-spark-project/kylin-spark-engine/src/main/scala/org/apache/kylin/engine/spark/builder/CubeTableEncoder.scala
##########
@@ -63,7 +67,20 @@ object CubeTableEncoder extends Logging {
           .select(columns: _*)
       }
     )
+
     ds.sparkSession.sparkContext.setJobDescription(null)
+
+    //repartition by a single column during dict encode step before is more easily to cause data skew, add step to void such case.
+    if (!cols.isEmpty && seg.kylinconf.rePartitionEncodedDatasetWithRowKey) {
+      val colsInDS = partitionedDs.schema.map(_.name)
+      val rowKeyColRefs = seg.allRowKeyCols.map(colDesc => convertFromDot(colDesc.identity)).filter(colsInDS.contains).map(col)
+      //if not set in config, use the largest partition num during dict encode step
+      if (seg.kylinconf.getRepartitionNumAfterEncode != 0) {

Review comment:
       change to `if (seg.kylinconf.getRepartitionNumAfterEncode < 1) {`, avoid to run failed when setting this value to -1.




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