crepererum opened a new issue, #6116:
URL: https://github.com/apache/arrow-datafusion/issues/6116

   ### Describe the bug
   
   `common_sub_expression_eliminate` pushes aggregate expressions into a child 
of the aggregate note which is wrong.
   
   ### To Reproduce
   
   See
   
   
https://github.com/apache/arrow-datafusion/blob/0d93dede46aae547d0ac167aa3e3e502efdffb97/datafusion/optimizer/src/common_subexpr_eliminate.rs#L707-L728
   
   ### Expected behavior
   
   ```rust
   let expected = "Projection: Int32(1) + AVG(test.a), Int32(1) - AVG(test.a)\
   \n  Aggregate: groupBy=[[]], aggr=[[AVG(test.a) AS AVG(test.a)]]\
           \n    TableScan: test";
   ```
   
   In general it should push the expression used within aggregate (and 
aggregate UDFs) into a child while placing the users of the aggregates into a 
parent. So a more complex test case may look like this:
   
   ```rust
   #[test]
   fn aggregate() -> Result<()> {
       let table_scan = test_table_scan()?;
   
       let inner = binary_expr(lit(1), Operator::Plus, avg(col("a")));
       let plan = LogicalPlanBuilder::from(table_scan)
           .aggregate(
               iter::empty::<Expr>(),
               vec![
                   binary_expr(lit(1), Operator::Plus, avg(inner)),
                   binary_expr(lit(1), Operator::Minus, avg(inner)),
                   min(inner),
               ],
           )?
           .build()?;
   
       let expected = "Projection: Int32(1) + AVG(TMP), Int32(1) - AVG(TMP), 
MIN(TMP)\
       \n  Aggregate: groupBy=[[]], aggr=[[AVG(TMP) as AVG(TMP), MIN(TMP) as 
MIN(TMP)]]\
       \n    Projection: Int32(1) + test.a AS TMP, test.a, test.b, test.c\
       \n      TableScan: test";
   
       assert_optimized_plan_eq(expected, &plan);
   
       Ok(())
   }
   ```
   
   (I somewhat improvised the column naming here to be able to write this down 
quicker)
   
   ### Additional context
   
   For SQL queries this doesn't seem to be an issue because this kind of 
de-duplication seems already be done during lowering, e.g. this code
   
   ```sql
   SELECT AVG(c1 + 1) + 1, AVG(c1 + 1) + 2 FROM test
   ```
   
   produces this initial plan:
   
   ```text
   Projection: AVG(test.c1 + Int64(1)) + Int64(1), AVG(test.c1 + Int64(1)) + 
Int64(2)
     Aggregate: groupBy=[[]], aggr=[[AVG(test.c1 + Int64(1))]]
       TableScan: test
   ```


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