feat(ffi): plumb simplify, expressions, reverse_expr, and documentation through FFI_WindowUDF#22705
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feat(ffi): plumb simplify, expressions, reverse_expr, and documentation through FFI_WindowUDF#22705Brijesh-Thakkar wants to merge 5 commits into
simplify, expressions, reverse_expr, and documentation through FFI_WindowUDF#22705Brijesh-Thakkar wants to merge 5 commits into
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…hrough FFI_WindowUDF Closes apache#22332 Add documentation, expressions, simplify, and reverse_expr fn pointers to FFI_WindowUDF struct Implement producer-side wrappers for each new fn pointer Wire ForeignWindowUDF trait methods to call the fn pointers Add FFI_ExpressionArgs in a new expression_args.rs sibling module to carry Vec<Arc<dyn PhysicalExpr>> across the boundary Add FFI_ReversedUDWF enum (#[repr(C, u8)]) to represent the three ReversedUDWF variants stably simplify executes on the producer side and returns a serialized Expr; the consumer closure deserializes and returns the result Unit tests (local-bypass + forced-foreign) for all four methods Integration test for documentation in ffi_udwf.rs Note: ForeignWindowUDF::simplify() uses DefaultLogicalExtensionCodec internally; UDWFs requiring a custom codec are a known follow-up. API change: FFI_WindowUDF struct layout modified — target main only, no backport.
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Pull request overview
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This PR extends the UDWF FFI surface to expose additional WindowUDFImpl capabilities (documentation, expressions, simplify, and reverse), and adds tests to validate cross-FFI behavior.
Changes:
- Add new FFI entry points for
documentation,expressions,simplify, andreverse_expronFFI_WindowUDF - Introduce an
FFI_ExpressionArgswrapper for passingExpressionArgsacross FFI - Add/extend tests to cover the new UDWF FFI behaviors
Reviewed changes
Copilot reviewed 3 out of 3 changed files in this pull request and generated 6 comments.
| File | Description |
|---|---|
| datafusion/ffi/src/udwf/mod.rs | Adds new UDWF FFI function pointers + wrappers, plus ForeignWindowUDF implementations for the new trait methods |
| datafusion/ffi/src/udwf/expression_args.rs | New FFI-stable container to pass ExpressionArgs across the FFI boundary |
| datafusion/ffi/tests/ffi_udwf.rs | Adds a test ensuring UDWF documentation survives the FFI wrapping/unwrapping path |
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| impl TryFrom<ExpressionArgs<'_>> for FFI_ExpressionArgs { | ||
| type Error = DataFusionError; | ||
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| fn try_from(args: ExpressionArgs) -> Result<Self, DataFusionError> { |
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| unsafe extern "C" fn expressions_fn_wrapper( | ||
| udwf: &FFI_WindowUDF, | ||
| args: FFI_ExpressionArgs, | ||
| ) -> SVec<FFI_PhysicalExpr> { | ||
| unsafe { | ||
| let inner = udwf.inner(); | ||
| let args = ForeignExpressionArgs::try_from(args).unwrap(); | ||
| let expressions = inner.expressions((&args).into()); | ||
| expressions.into_iter().map(FFI_PhysicalExpr::from).collect() | ||
| } | ||
| } |
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| fn expressions( | ||
| &self, | ||
| expr_args: datafusion_expr::function::ExpressionArgs, | ||
| ) -> Vec<Arc<dyn PhysicalExpr>> { | ||
| unsafe { | ||
| let args = FFI_ExpressionArgs::try_from(expr_args).unwrap(); | ||
| (self.udf.expressions)(&self.udf, args) | ||
| .into_iter() | ||
| .map(|e| Arc::<dyn PhysicalExpr>::from(&e)) | ||
| .collect() | ||
| } | ||
| } |
| /// user defined signatures, which will in turn call coerce_types to be called. This | ||
| /// call should be transparent to most users as the internal function performs the | ||
| /// appropriate calls on the underlying [`WindowUDF`] | ||
| pub documentation: unsafe extern "C" fn(udwf: &Self) -> *const Documentation, |
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| fn simplify(&self) -> Option<WindowFunctionSimplification> { | ||
| let udf = self.udf.clone(); | ||
| Some(Box::new(move |wf, info| { |
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| pub documentation: unsafe extern "C" fn(udwf: &Self) -> *const Documentation, | ||
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| pub expressions: unsafe extern "C" fn( | ||
| udwf: &Self, | ||
| args: FFI_ExpressionArgs, | ||
| ) -> SVec<FFI_PhysicalExpr>, | ||
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| pub simplify: unsafe extern "C" fn( | ||
| udwf: &Self, | ||
| window_function: SVec<u8>, | ||
| schema: WrappedSchema, | ||
| ) -> FFI_Result<FFI_Option<SVec<u8>>>, | ||
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| pub reverse_expr: unsafe extern "C" fn(udwf: &Self) -> FFI_ReversedUDWF, |
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Thank you for opening this pull request! Reviewer note: cargo-semver-checks reported the current version number is not SemVer-compatible with the changes in this pull request (compared against the base branch). Details |
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@timsaucer Please review it and suggest if any changes are required |
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Which issue does this PR close?
Closes #22332
Rationale for this change
FFI_WindowUDFwas silently dropping producer overrides of four defaultedWindowUDFImplmethods. Any plugin that overrodeexpressions(),simplify(),reverse_expr(), ordocumentation()would have thoseoverrides ignored on the consumer side, with the trait defaults running
instead. This could change window-function semantics (e.g.
expressions()selects which physical expressions reach the
PartitionEvaluator) orsilently suppress planner-level optimizations (
simplify,reverse_expr).What changes are included in this PR?
documentation— newunsafe extern "C"fn pointer returning*const Documentation(null =None); consumer reconstructs viaptr.as_ref()expressions— new fn pointer takingFFI_ExpressionArgsandreturning
SVec<FFI_PhysicalExpr>; a new sibling moduleudwf/expression_args.rsprovidesFFI_ExpressionArgs/ForeignExpressionArgsto carryVec<Arc<dyn PhysicalExpr>>andVec<FieldRef>across the boundarysimplify— closures cannot cross FFI, so simplification executeson the producer side: the consumer serializes the
WindowFunctiontoprotobuf bytes, calls the fn pointer, and deserializes the returned
Expr; the producer wrapper deserializes, calls the innersimplifyclosure, and returns the serialized result
reverse_expr— newFFI_ReversedUDWFenum (#[repr(C, u8)],matching the existing ABI-stable enum pattern in this crate) with
variants
Identical,NotSupported, andReversed(FFI_WindowUDF);the
Reversedvariant uses the round-trip downcast optimization toavoid double-wrapping when the inner UDF is already a
ForeignWindowUDFKnown limitation:
ForeignWindowUDF::simplify()currently usesDefaultLogicalExtensionCodecinternally. UDWFs whose expressions requirea custom codec to round-trip are not yet supported through the simplify
path and are tracked as a follow-up.
Are these changes tested?
Yes. For each of the four methods:
datafusion/ffi/src/udwf/mod.rscover both thelocal-bypass path (marker IDs match, downcasts to concrete type) and
the forced-foreign path (
mock_foreign_marker_idset, full FFI pathexercised)
datafusion/ffi/tests/ffi_udwf.rscoversdocumentationacross the crate boundaryAre there any user-facing changes?
FFI_WindowUDFstruct layout has changed — this is an ABI-breaking changefor anyone linking against the struct directly. The PR targets
mainonlywith no backport, per the
datafusion-fficrate convention for layoutchanges.