jayzhan211 commented on code in PR #14232:
URL: https://github.com/apache/datafusion/pull/14232#discussion_r1929432984


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datafusion/functions-aggregate/src/first_last.rs:
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@@ -569,6 +573,13 @@ impl LastValueAccumulator {
             })
             .collect::<Vec<_>>();
 
+        // Order by indices for cases where the values are the same, we expect 
the last index
+        let indices: UInt64Array = (0..num_rows).map(|x| x as u64).collect();
+        sort_columns.push(SortColumn {

Review Comment:
   Okay, it seems like unstable sort is used in arrow-rs probably we need 
another stable sort in arrow-rs to not impact the current single column case.
   
   Alternative solution is that the users can add another column by themselves 
to get the **true** last value if they need for their scenario 🤔 Then we can 
keep the last value as an **unstable** version by default



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