stczwd opened a new pull request #26946: [SPARK-30036][SQL] Fix: REPARTITION 
hint does not work with order by
URL: https://github.com/apache/spark/pull/26946
 
 
   ### Why are the changes needed?
   EnsureRequirements adds ShuffleExchangeExec (RangePartitioning) after Sort 
if RoundRobinPartitioning behinds it. This will cause 2 shuffles, and the 
number of partitions in the final stage is not the number specified by 
RoundRobinPartitioning.
   Example SQL: select /*+ REPARTITION(5) */ * from test order by a
   Before fix:
   == Physical Plan ==
   *(1) Sort [a#0 ASC NULLS FIRST], true, 0
   +- Exchange rangepartitioning(a#0 ASC NULLS FIRST, 200), true, [id=#11]
      +- Exchange RoundRobinPartitioning(5), false, [id=#9]
         +- Scan hive default.test [a#0, b#1], HiveTableRelation 
`default`.`test`, org.apache.hadoop.hive.serde2.lazy.LazySimpleSerDe, [a#0, b#1]
   After fix:
   == Physical Plan ==
   *(1) Sort [a#0 ASC NULLS FIRST], true, 0
   +- Exchange rangepartitioning(a#0 ASC NULLS FIRST, 5), true, [id=#11]
      +- Scan hive default.test [a#0, b#1], HiveTableRelation `default`.`test`, 
org.apache.hadoop.hive.serde2.lazy.LazySimpleSerDe, [a#0, b#1]
   
   ### Does this PR introduce any user-facing change?
   No
   
   ### How was this patch tested?
   Run suite Tests and add new test for this.
   

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