(arrow-rs) branch main updated: feat: add null comparison handling in make_comparator (#9150)

[alamb]

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alamb pushed a commit to branch main
in repository https://gitbox.apache.org/repos/asf/arrow-rs.git


The following commit(s) were added to refs/heads/main by this push:
     new 9b633fb8f7 feat: add null comparison handling in make_comparator 
(#9150)
9b633fb8f7 is described below

commit 9b633fb8f7457ebe49fcd28e65c74f6e8d77964e
Author: Alex Huang <huangweijun1...@gmail.com>
AuthorDate: Thu Jan 15 00:00:02 2026 +0200

    feat: add null comparison handling in make_comparator (#9150)
    
    # Which issue does this PR close?
    
    <!--
    We generally require a GitHub issue to be filed for all bug fixes and
    enhancements and this helps us generate change logs for our releases.
    You can link an issue to this PR using the GitHub syntax.
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    - Closes #NNN.
    
    # Rationale for this change
    
    `make_comparator` currently does not support Null data type, returning
    an error when comparing two NullArrays. This prevents sorting or
    comparing arrays that contain Null type columns.
    
    
    
    <!--
    Why are you proposing this change? If this is already explained clearly
    in the issue then this section is not needed.
    Explaining clearly why changes are proposed helps reviewers understand
    your changes and offer better suggestions for fixes.
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    # What changes are included in this PR?
    
    Add support for Null data type in `make_comparator`. Since all values in
    a NullArray are semantically null and indistinguishable, any comparison
    returns `Ordering::Equal`.
    
    
    
    <!--
    There is no need to duplicate the description in the issue here but it
    is sometimes worth providing a summary of the individual changes in this
    PR.
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    # Are these changes tested?
    
    Yes
    
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    1. Prevent the code from being accidentally broken by subsequent changes
    2. Serve as another way to document the expected behavior of the code
    
    If tests are not included in your PR, please explain why (for example,
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    # Are there any user-facing changes?
    
    Yes. `make_comparator` now accepts Null type arrays instead of returning
    an error. This is a non-breaking enhancement.
    
    
    
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    If there are user-facing changes then we may require documentation to be
    updated before approving the PR.
    
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---
 arrow-ord/src/ord.rs | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/arrow-ord/src/ord.rs b/arrow-ord/src/ord.rs
index b12a06732d..c09fff807a 100644
--- a/arrow-ord/src/ord.rs
+++ b/arrow-ord/src/ord.rs
@@ -484,6 +484,7 @@ pub fn make_comparator(
              }
         },
         (Map(_, _), Map(_, _)) => compare_map(left, right, opts),
+        (Null, Null) => Ok(Box::new(|_, _| Ordering::Equal)),
         (Union(_, _), Union(_, _)) => compare_union(left, right, opts),
         (lhs, rhs) => Err(ArrowError::InvalidArgumentError(match lhs == rhs {
             true => format!("The data type type {lhs:?} has no natural order"),
@@ -1501,4 +1502,15 @@ mod tests {
             "Cannot compare UnionArrays with different modes: left=Dense, 
right=Sparse"
         );
     }
+
+    #[test]
+    fn test_null_array_cmp() {
+        let a = NullArray::new(3);
+        let b = NullArray::new(3);
+        let cmp = make_comparator(&a, &b, SortOptions::default()).unwrap();
+
+        assert_eq!(cmp(0, 0), Ordering::Equal);
+        assert_eq!(cmp(0, 1), Ordering::Equal);
+        assert_eq!(cmp(2, 0), Ordering::Equal);
+    }
 }