edmondop commented on issue #8157:
URL:
https://github.com/apache/arrow-datafusion/issues/8157#issuecomment-1843411377
@alamb I checked out and on main the structs and enums are already written
as you recommended
```rust
pub enum ScalarFunctionDefinition {
/// Resolved to a built in scalar function
/// (will be removed long term)
BuiltIn(built_in_function::BuiltinScalarFunction),
/// Resolved to a user defined function
UDF(ScalarUDF),
/// A scalar function that will be called by name
Name(Arc<str>),
}
#[derive(Clone, PartialEq, Eq, Hash, Debug)]
pub struct ScalarFunction {
/// The function
pub fun: ScalarFunctionDefinition,
/// List of expressions to feed to the functions as arguments
pub args: Vec<Expr>,
}
```
So I am not sure I understood correctly. I could see that `call_fn` resolves
at invocation site rather than at planning site, and changing the behavior
would probably mean changing this code. What is the right type of Expr this
code should return?
```rust
/// Calls a named built in function
/// ```
/// use datafusion_expr::{col, lit, call_fn};
///
/// // create the expression sin(x) < 0.2
/// let expr = call_fn("sin", vec![col("x")]).unwrap().lt(lit(0.2));
/// ```
pub fn call_fn(name: impl AsRef<str>, args: Vec<Expr>) -> Result<Expr> {
match name.as_ref().parse::<BuiltinScalarFunction>() {
Ok(fun) => Ok(Expr::ScalarFunction(ScalarFunction::new(fun, args))),
Err(e) => Err(e),
}
}
```
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