viirya commented on code in PR #8578:
URL: https://github.com/apache/arrow-datafusion/pull/8578#discussion_r1430589301
##########
datafusion/expr/src/udf.rs:
##########
@@ -124,22 +169,116 @@ impl ScalarUDF {
&self.aliases
}
- /// Returns this function's signature (what input types are accepted)
+ /// Returns this function's [`Signature`] (what input types are accepted)
pub fn signature(&self) -> &Signature {
&self.signature
}
- /// Return the type of the function given its input types
+ /// The datatype this function returns given the input argument input types
pub fn return_type(&self, args: &[DataType]) -> Result<DataType> {
// Old API returns an Arc of the datatype for some reason
let res = (self.return_type)(args)?;
Ok(res.as_ref().clone())
}
- /// Return the actual implementation
+ /// Return an [`Arc`] to the function implementation
pub fn fun(&self) -> ScalarFunctionImplementation {
self.fun.clone()
}
+}
+
+impl<F> From<F> for ScalarUDF
+where
+ F: ScalarUDFImpl + Send + Sync + 'static,
+{
+ fn from(fun: F) -> Self {
+ Self::new_from_trait(fun)
+ }
+}
+
+/// Trait for implementing [`ScalarUDF`].
+///
+/// This trait exposes the full API for implementing user defined functions and
+/// can be used to implement any function.
+///
+/// See [`advanced_udf.rs`] for a full example with implementation. See
+/// [`ScalarUDF`] for details on a simpler API.
Review Comment:
For simpler API, do you mean `create_udf`?
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