pepijnve commented on code in PR #18921:
URL: https://github.com/apache/datafusion/pull/18921#discussion_r3004965802
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datafusion/expr/src/expr.rs:
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@@ -404,6 +406,104 @@ pub enum Expr {
OuterReferenceColumn(FieldRef, Column),
/// Unnest expression
Unnest(Unnest),
+ /// Call a lambda function with a set of arguments.
+ ///
+ /// For example, `array_transform([1,2,3], v -> v+1)` would be equivalent
to:
+ ///
+ /// ```text
+ /// LambdaFunction(array_transform)
+ /// ├── args[0]: Literal([1,2,3])
+ /// └── args[1]: Lambda
+ /// ├── params: ["v"]
+ /// └── body: BinaryExpr(+)
+ /// ├── LambdaVariable("v")
+ /// └── Literal(1)
+ /// ```
+ LambdaFunction(LambdaFunction),
Review Comment:
Should we call this a higher-order function instead? Calling it a 'lambda
function' is bit misleading. In the literature at least that's the name used
for the `Lambda` type below.
Is this going to be limited to only anonymous inline functions or will it be
possible to pass a scalar UDF name as the function parameter as well?
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