[GitHub] [arrow-datafusion] alamb commented on a diff in pull request #5607: [FOLLOWUP] eliminate the duplicated sort keys in Order By clause

["alamb (via GitHub)" <gi...@apache.org>]

alamb commented on code in PR #5607:
URL: https://github.com/apache/arrow-datafusion/pull/5607#discussion_r1137331638


##########
datafusion/optimizer/src/eliminate_duplicated_expr.rs:
##########
@@ -41,15 +42,28 @@ impl OptimizerRule for EliminateDuplicatedExpr {
     ) -> Result<Option<LogicalPlan>> {
         match plan {
             LogicalPlan::Sort(sort) => {
+                let normalized_sort_keys = sort
+                    .expr
+                    .iter()
+                    .map(|e| match e {
+                        Expr::Sort(ExprSort { expr, .. }) => {
+                            Expr::Sort(ExprSort::new(expr.clone(), true, false))

Review Comment:
   I am not sure about always using `true`, `fase`
   
   Using the example
   ```sql
   select * from t1 order by id desc, id, name, id asc;
   select * from t1 order by id asc, id, name, id desc;
   ```
   
   Is the sort key always the same ? It seems like in the first query the sort key should be `id desc, name` and the second it should be `id asc, name`
   
   Maybe I am missing something



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