wankunde opened a new pull request, #43009:
URL: https://github.com/apache/spark/pull/43009

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   ### What changes were proposed in this pull request?
   
   This PR could be a followup of https://github.com/apache/spark/pull/42488 
and https://github.com/apache/spark/pull/42557.
   
   If there is an aggregate operator after the SMJ and the grouping expressions 
of aggregate operator contain all the join keys of the streamed side, we can 
add a sorter on the streamed side of the SMJ, so that the aggregate can be 
convert to a SortAggregate which will be faster than HashAggregate.
   
   For example, with table t1(a, b, c) and t2(x, y, z):
   ```
   SELECT a, b, sum(c)
   FROM t1
   JOIN t2
   ON t1.b = t2.y
   GROUP BY a, b
   ```
   
   The optimized plan:
   ```
   Scan(t1)                Scan(t2)
       |                      |
       |                      |
   Exchange 1           Exchange 2
        \                     /
          \                 /
            \             /
           SMJ (t1.b = t2.y)
                   |
                   |
               Aggregate
   ```
   Before this PR, spark EnsureReqirement will add Sorter(t1.b) to the left 
side of SMJ.
   ```
   Scan(t1)                Scan(t2)
       |                      |
       |                      |
   Exchange 1           Exchange 2
        \                     /
      Sort(t1.b)        Sort(t2.y) 
            \             /
          SMJ (t1.b = t2.y)
                   |
                   |
            HashAggregate
   ```
   
   If we add a Sort(t1.b, t1.a) to the left side of the SMJ, the following 
aggregate could be convert to SortAggregate, will be faster.
   
   ```
   Scan(t1)                Scan(t2)
       |                      |
       |                      |
   Exchange 1           Exchange 2
        \                    /
    Sort(t1.b, t1.a)   Sort(t2.y) 
            \             /
         SMJ (t1.b = t2.y)
                   |
                   |
             SortAggregate
   ```
   
   
   ### Why are the changes needed?
   
   Optimize HashAggregate
   
   
   ### Does this PR introduce _any_ user-facing change?
   
   No
   
   ### How was this patch tested?
   
   Added UT
   
   
   ### Was this patch authored or co-authored using generative AI tooling?
   
   No
   


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