Brijesh-Thakkar commented on code in PR #22705:
URL: https://github.com/apache/datafusion/pull/22705#discussion_r3390522199
##########
datafusion/ffi/src/udwf/mod.rs:
##########
@@ -358,6 +488,83 @@ impl WindowUDFImpl for ForeignWindowUDF {
}
}
+ fn documentation(&self) -> Option<&Documentation> {
+ unsafe {
+ let ptr = (self.udf.documentation)(&self.udf);
+ ptr.as_ref()
+ }
+ }
+
+ fn expressions(
+ &self,
+ expr_args: datafusion_expr::function::ExpressionArgs,
+ ) -> Vec<Arc<dyn PhysicalExpr>> {
+ unsafe {
+ let fallback = expr_args.input_exprs().to_vec();
+ let args = match FFI_ExpressionArgs::try_from(expr_args) {
+ Ok(args) => args,
+ Err(_) => return fallback,
+ };
+ (self.udf.expressions)(&self.udf, args)
+ .into_iter()
+ .map(|e| Arc::<dyn PhysicalExpr>::from(&e))
+ .collect()
+ }
+ }
+
+ fn simplify(&self) -> Option<WindowFunctionSimplification> {
+ if !self.udf.has_simplify {
+ return None;
+ }
+
+ let udf = self.udf.clone();
+ Some(Box::new(move |wf, info| {
+ let codec =
datafusion_proto::logical_plan::DefaultLogicalExtensionCodec {};
+
+ // To serialize the window function
+ let expr = Expr::WindowFunction(Box::new(wf));
+ let protobuf =
datafusion_proto::logical_plan::to_proto::serialize_expr(
+ &expr, &codec,
+ )
Review Comment:
WindowFunctionSimplification is a Box<dyn Fn(WindowFunction, &dyn
SimplifyInfo) -> Result<Expr>>. Closures cannot cross FFI boundaries directly,
so the only viable approach is: the consumer serializes the WindowFunction to
bytes, calls the fn pointer, and the producer deserializes, executes its
closure, and returns the serialized Expr. Would you prefer we skip cross-FFI
simplify in this PR and document it as a known follow-up (returning None from
ForeignWindowUDF::simplify() while keeping the has_simplify capability flag),
or is the serialization approach acceptable with the codec fixed?
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