jzhan-2026 opened a new pull request, #59108:
URL: https://github.com/apache/spark/pull/59108
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### What changes were proposed in this pull request?
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Three related improvements to the Python UDF transpiler:
1. **Null narrowing.** When a parameter is guarded by `x is not None` (or `x
is None`) in an `if`/ternary test, the transpiler tracks that the parameter is
proven non-null in the appropriate branch. Ordering comparisons (`<`, `<=`,
`>`, `>=`) and `len()` calls on such parameters skip the `raise_error` null
guard entirely.
2. **2-statement early-return normalization.** A common guard idiom:
```python
if x is None:
return default
return x > 0
is normalized into a single if/else before lowering, so null narrowing
applies to the main body.
3. UserWarning on null guard emission. When a null guard is still emitted
(non-null cannot be proven), the transpiler warns at UDF construction time.
Co-authored with [email protected]
### Why are the changes needed?
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Any ordering comparison in a transpiled UDF previously always emitted a
raise_error guard, even when the code already checked x is not None. This
produced unnecessary plan nodes and blocked clean transpilation of the most
common Python null-guard idiom.
### Does this PR introduce _any_ user-facing change?
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Yes. UDFs with is not None-guarded comparisons produce leaner plans (no
raise_error node in the guarded branch). The UserWarning at construction time
is new when unguarded comparisons remain. Behavior on non-null inputs is
unchanged.
### How was this patch tested?
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Four new test cases in test_udf_transpile_unit.py:
- test_udf_transpile_null_narrowing_skips_null_guard — if/ternary with is
not None guard: plan has no raise_error, results match Python
- test_udf_transpile_early_return_null_guard — 2-stmt early-return pattern
transpiles with no raise_error
- test_udf_transpile_null_guard_warning — unguarded comparison emits
UserWarning
- test_udf_transpile_null_narrowing_len — guarded len() has no raise_error
in plan
### Was this patch authored or co-authored using generative AI tooling?
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Co-authored by: Claude Sonnet 4.6
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