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fix(spark): derive concat_ws nullability from separator - #26205

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neilconway merged 1 commit into
apache:mainfrom
VVKot:vkot/fix-concat-ws-nullability
Oct 11, 2026
Merged

neilconway merged 1 commit into
apache:mainfrom
VVKot:vkot/fix-concat-ws-nullability

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@VVKot

@VVKot VVKot commented Oct 11, 2026

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Which issue does this PR close?

Part of the work towards #15914

Rationale for this change

concat_ws return value is always nullable in DF, which is incorrect. Per upstream Spark implementation, this is only true when separator itself is null.

What changes are included in this PR?

Derive the nullability based on the separator nullability.

What is the testing strategy for this PR?

Add SLT tests for schema.

Are there any user-facing changes?

I believe this doesn't count as an API change but would like guidance from a committer.

@github-actions github-actions Bot added sqllogictest SQL Logic Tests (.slt) spark labels Oct 11, 2026
@VVKot

VVKot commented Oct 11, 2026

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@Jefffrey @neilconway maybe one of you can take a look?

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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.80%. Comparing base (75ddead) to head (eb92c6b).

Additional details and impacted files
@@            Coverage Diff             @@
##             main   #26205      +/-   ##
==========================================
- Coverage   82.80%   82.80%   -0.01%     
==========================================
  Files        1149     1149              
  Lines      452205   452213       +8     
  Branches   452205   452213       +8     
==========================================
+ Hits       374458   374459       +1     
- Misses      54950    54956       +6     
- Partials    22797    22798       +1     

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@neilconway neilconway left a comment

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Thanks @VVKot , lgtm.

Btw, Spark's soundex and space, and core's concat_ws, might benefit from a similar change.

@neilconway
neilconway added this pull request to the merge queue Oct 11, 2026
Merged via the queue into apache:main with commit 454ca08 Oct 11, 2026
42 checks passed
Omega359 pushed a commit to Omega359/arrow-datafusion that referenced this pull request Oct 11, 2026
## 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. For example
`Closes apache#123` indicates that this PR will close issue apache#123.
-->

Part of the work towards
apache#15914

## Rationale for this change

<!--
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.

Please explain the problem you are trying to solve in terms of the
user-visible
behavior, rather than the implementation.

For example, "The code in `foo.rs` doesn't handle nulls" is a symptom of
the
implementation. "COUNT(DISTINCT) returns wrong results when the column
contains
nulls" is the user-visible problem.
-->

`concat_ws` return value is always nullable in DF, which is incorrect.
Per upstream Spark implementation, this is only true when separator
itself is null.

## What changes are included in this PR?

<!--
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.
-->

Derive the nullability based on the separator nullability.

## What is the testing strategy for this PR?

<!--
We typically require tests for all PRs in order to:
1. Prevent the code from being accidentally broken by subsequent changes
2. Serve as another way to document the expected behavior of the code

Briefly describe how this PR is tested, and point to the specific tests
you added. For example: 'This new feature is covered by the
`sqllogictest` cases added in `foo.slt`'.

If this PR does not add tests, explain why. For example, if the change
is already covered by existing tests, please mention it.

You should also check the `codecov` bot reply on this PR to confirm the
changed code is exercised.
-->

Add SLT tests for schema.

## Are there any user-facing changes?

<!--
If there are user-facing changes then we may require documentation to be
updated before approving the PR.

If there are any breaking changes to public APIs, please add the `api
change` label.
-->

I believe this doesn't count as an API change but would like guidance
from a committer.
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3 participants