[GitHub] [arrow-datafusion] Dandandan commented on a diff in pull request #6065: Optimize row hash

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

Dandandan commented on code in PR #6065:
URL: https://github.com/apache/arrow-datafusion/pull/6065#discussion_r1171833111


##########
datafusion/core/src/physical_plan/aggregates/row_hash.rs:
##########
@@ -772,22 +773,22 @@ fn slice_and_maybe_filter(
     filter_opt: Option<&Arc<dyn Array>>,
     offsets: &[usize],
 ) -> Result<Vec<ArrayRef>> {
-    let sliced_arrays: Vec<ArrayRef> = aggr_array
-        .iter()
-        .map(|array| array.slice(offsets[0], offsets[1] - offsets[0]))
-        .collect();
+    let null_array = Arc::new(NullArray::new(0)) as ArrayRef;
+    let mut sliced_arrays: Vec<ArrayRef> = vec![null_array; aggr_array.len()];

Review Comment:
   I don't see why this should be faster? 🤔



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