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Posted to github@datafusion.apache.org by "andygrove (via GitHub)" <gi...@apache.org> on 2025/12/27 19:05:36 UTC
[PR] perf: Optimize `contains` for scalar search arg [datafusion]
andygrove opened a new pull request, #19514:
URL: https://github.com/apache/datafusion/pull/19514
## Which issue does this PR close?
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## Rationale for this change
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`ContainsFunc` used `make_scalar_function`, which expands scalar arguments into arrays before calling Arrow's `contains` function, defeating Arrow's built-in scalar optimization.
| Case | Before | After | Speedup |
|---------------------------------|-------------|-------------|---------------|
| StringArray + scalar search | 259 µs | 41 µs | 6.3x |
| StringViewArray + scalar search | 339 µs | 41 µs | 8.3x |
| Array + array search | ~260-300 µs | ~265-305 µs | No regression |
## What changes are included in this PR?
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Rewrote invoke_with_args to:
1. Handle the four cases directly (scalar/scalar, array/scalar, scalar/array, array/array)
2. Use Arrow's Scalar<ArrayRef> wrapper when passing scalar arguments
3. Let Arrow's contains function use its optimized op_scalar path when the second argument is a scalar
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Re: [PR] perf: Optimize `contains` for scalar search arg [datafusion]
Posted by "andygrove (via GitHub)" <gi...@apache.org>.
andygrove commented on PR #19514:
URL: https://github.com/apache/datafusion/pull/19514#issuecomment-3694864572
> > Thanks @andygrove the numbers make huge sense to me, what prob concerns is DF using `make_scalar_function` in lots of places so the same problem can be relevant for others.
> > Would you mind adding more details what is the exact reason and what scalar/array combinations are the most trouble?
> > this info might be important how DF treats bultin functions now
>
> Basically, the `make_scalar_function` functions (there are three implementations, two of which are identical and one with slightly different behavior) convert scalar arguments into arrays. This adds unnecessary overhead in some cases because Arrow has specialized implementations of some kernels with fast paths for scalar arguments. For example, for `contains`, Arrow has `pub fn contains(left: &dyn Datum, right: &dyn Datum)` and `Datum` is implemented for arrays and scalars. The implementation has special handling for scalars.
>
> The three implementations of `make_scalar_function` can be found in these files:
>
> * `datafusion/functions/src/utils.rs`
>
> * `datafusion/functions-nested/src/utils.rs`
>
> * `datafusion/spark/src/function/functions_nested_utils.rs`
The issue is that `make_scalar_function` expected ArrayRefs:
```
F: Fn(&[ArrayRef]) -> Result<ArrayRef>,
```
It would perhaps be better if it accepted `ColumnarValue`, which supports both arrays and scalars. This is probably a large refactor.
```
F: Fn(&[ColumnarValue]) -> Result<ArrayRef>,
```
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Re: [PR] perf: Optimize `contains` for scalar search arg [datafusion]
Posted by "andygrove (via GitHub)" <gi...@apache.org>.
andygrove commented on PR #19514:
URL: https://github.com/apache/datafusion/pull/19514#issuecomment-3694893516
@comphead I created an alternate PR that creates a new version of `make_scalar_function` that does not expand scalars: https://github.com/apache/datafusion/pull/19529
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Re: [PR] perf: Optimize `contains` for scalar search arg [datafusion]
Posted by "andygrove (via GitHub)" <gi...@apache.org>.
andygrove commented on PR #19514:
URL: https://github.com/apache/datafusion/pull/19514#issuecomment-3694848340
> Thanks @andygrove the numbers make huge sense to me, what prob concerns is DF using `make_scalar_function` in lots of places so the same problem can be relevant for others.
>
> Would you mind adding more details what is the exact reason and what scalar/array combinations are the most trouble?
>
> this info might be important how DF treats bultin functions now
Basically, the `make_scalar_function` functions (there are three implementations, two of which are identical and one with slightly different behavior) convert scalar arguments into arrays. This adds unnecessary overhead in some cases because Arrow has specialized implementations of some kernels with fast paths for scalar arguments. For example, for `contains`, Arrow has `pub fn contains(left: &dyn Datum, right: &dyn Datum)` and `Datum` is implemented for arrays and scalars. The implementation has special handling for scalars.
The three implementations of `make_scalar_function` can be found in these files:
- `datafusion/functions/src/utils.rs`
- `datafusion/functions-nested/src/utils.rs`
- `datafusion/spark/src/function/functions_nested_utils.rs`
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Re: [PR] perf: Optimize `contains` for scalar search arg [datafusion]
Posted by "andygrove (via GitHub)" <gi...@apache.org>.
andygrove closed pull request #19514: perf: Optimize `contains` for scalar search arg
URL: https://github.com/apache/datafusion/pull/19514
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