[GitHub] [spark] dongjoon-hyun commented on pull request #29089: [SPARK-32276][SQL] Remove redundant sorts before repartition nodes

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dongjoon-hyun commented on pull request #29089:
URL: https://github.com/apache/spark/pull/29089#issuecomment-658543717


   Oops. Sorry, guys. It seems that I missed something during testing. For the 
following case, we should not remove `Sort`.
   
   **BEFORE THIS PR**
   ```scala
   scala> Seq((1,10),(1,20),(2,30),(2,40)).toDF("a", 
"b").repartition(2).createOrReplaceTempView("t")
   
   scala> sql("select * from (select * from t order by b desc) distribute by 
a").show()
   +---+---+
   |  a|  b|
   +---+---+
   |  1| 20|
   |  1| 10|
   |  2| 40|
   |  2| 30|
   +---+---+
   ```
   
   **AFTER THIS PR**
   ```scala
   scala> Seq((1,10),(1,20),(2,30),(2,40)).toDF("a", 
"b").repartition(2).createOrReplaceTempView("t")
   
   scala> sql("select * from (select * from t order by b desc) distribute by 
a").show()
   +---+---+
   |  a|  b|
   +---+---+
   |  1| 10|
   |  1| 20|
   |  2| 30|
   |  2| 40|
   +---+---+
   ```
   


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