[GitHub] [arrow-datafusion] ozankabak commented on a diff in pull request #4846: Implement retract_batch for AvgAccumulator

[GitBox <gi...@apache.org>]

ozankabak commented on code in PR #4846:
URL: https://github.com/apache/arrow-datafusion/pull/4846#discussion_r1064041043


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datafusion/physical-expr/src/aggregate/average.rs:
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@@ -154,6 +159,14 @@ impl Accumulator for AvgAccumulator {
         Ok(())
     }
 
+    fn retract_batch(&mut self, values: &[ArrayRef]) -> Result<()> {
+        let values = &values[0];
+        self.count -= (values.len() - values.data().null_count()) as u64;
+        let delta = sum_batch(values, &self.sum.get_datatype())?;
+        self.sum = self.sum.sub(&delta)?;

Review Comment:
   I like giving a name to the change (i.e. `delta`). I suggest doing the same in `update_batch`.



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