perf: Optimize scalar path for chr function#20073
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Jefffrey merged 2 commits intoapache:mainfrom Feb 1, 2026
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Getting this in CI |
martin-g
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Jan 30, 2026
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LGTM!
It would be good to add some SLT tests though.
There are only array based unit tests and there are no SLT tests.
The Spark ones are empty - https://github.com/apache/datafusion/blob/f0de02fd664afcc4aad61fd8d13503533ed1e8d5/datafusion/sqllogictest/test_files/spark/string/chr.slt
Jefffrey
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Jan 30, 2026
| let return_type = args.return_field.data_type(); | ||
| let [arg] = take_function_args(self.name(), args.args)?; | ||
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| match arg { |
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match arg {
ColumnarValue::Scalar(ScalarValue::Int64(Some(code_point))) => {
if let Ok(u) = u32::try_from(code_point)
&& let Some(c) = core::char::from_u32(u)
{
Ok(ColumnarValue::Scalar(ScalarValue::Utf8(Some(
c.to_string(),
))))
} else {
exec_err!("invalid Unicode scalar value: {code_point}")
}
}
ColumnarValue::Scalar(ScalarValue::Int64(None)) => {
Ok(ColumnarValue::Scalar(ScalarValue::Utf8(None)))
}
ColumnarValue::Array(array) => {
Ok(ColumnarValue::Array(chr(&[array])?))
}
_ => internal_err!("..."),
}- Easier to fold into match like this since we accept only one datatype; also unnecessary to double check the array datatype
- Also worth looking into refactoring
chr()function; no reason to pass in a slice when we can just pass the array
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Thank you for the feedback. |
Jefffrey
approved these changes
Jan 31, 2026
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Thanks @kumarUjjawal & @martin-g |
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Which issue does this PR close?
Rationale for this change
chrcurrently routes scalar inputs throughmake_scalar_function(chr, vec![]), which performs a scalar → size-1 array → scalar roundtrip. This adds unnecessary overhead for constant folding / scalar evaluation.This PR adds a match-based scalar fast path and removes reliance on
make_scalar_functionforchr, while keeping the array behavior unchanged.What changes are included in this PR?
ChrFunc::invoke_with_argsto:ColumnarValue::Scalar(Int64)directly (scalar fast path)ColumnarValue::Array(Int64Array)using the existing conversion logicbenches/chr.rs(chr/scalar) outside any size loopchr/scalarAre these changes tested?
Yes
Are there any user-facing changes?
No