alamb commented on code in PR #8985:
URL: https://github.com/apache/arrow-datafusion/pull/8985#discussion_r1486884992
##########
datafusion/expr/src/expr_schema.rs:
##########
@@ -37,19 +37,19 @@ use std::sync::Arc;
/// trait to allow expr to typable with respect to a schema
pub trait ExprSchemable {
/// given a schema, return the type of the expr
- fn get_type<S: ExprSchema>(&self, schema: &S) -> Result<DataType>;
+ fn get_type(&self, schema: &dyn ExprSchema) -> Result<DataType>;
Review Comment:
I had to change the traits to use `dyn` dispatch rather than generics so
that the UDF could use the same object (and e.g. not have to create its own
copy of these methods for Expr)
I expect this to have 0 performance impact, but I will run the planning
benchmarks to be sure if this acceptable
##########
datafusion/core/tests/user_defined/user_defined_scalar_functions.rs:
##########
@@ -494,6 +495,127 @@ async fn test_user_defined_functions_zero_argument() ->
Result<()> {
Ok(())
}
+#[derive(Debug)]
+struct TakeUDF {
Review Comment:
Here is an example of the feature working
##########
datafusion/expr/src/udf.rs:
##########
@@ -249,6 +261,22 @@ pub trait ScalarUDFImpl: Debug + Send + Sync {
/// the arguments
fn return_type(&self, arg_types: &[DataType]) -> Result<DataType>;
+ /// What [`DataType`] will be returned by this function, given the types of
+ /// the expr arguments
+ fn return_type_from_exprs(
Review Comment:
Update is I changed the signature to take `&dyn ExprSchema` which seems to
have worked just fine
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