alamb commented on code in PR #14440:
URL: https://github.com/apache/datafusion/pull/14440#discussion_r1939737630
##########
datafusion/expr-common/src/signature.rs:
##########
@@ -455,6 +461,46 @@ fn get_data_types(native_type: &NativeType) ->
Vec<DataType> {
}
}
+#[derive(Debug, Clone)]
+pub struct FunctionSignature {
+ pub parameters: Vec<ParameterSignature>,
+ /// The volatility of the function. See [Volatility] for more information.
+ pub volatility: Volatility,
+}
+
+pub type ParameterSignature = Vec<ParameterType>;
+
+#[derive(Debug, Clone, Eq, PartialOrd, Hash)]
+pub struct ParameterType {
+ pub param_type: LogicalTypeRef,
Review Comment:
I am worried that `Vec<Vec<ParameterType>>` might become challenging to
reason about. It would also be confusing about when one use this new signature
rather than `Signature::Coercable` 🤔
Given this seems very similar to `Signature::Coercable`, and
`Signature::Coercable` mirrors what we want pretty well, could add some new
information there on the allowed coercions rather than an entire new type
signature. Something like extending `Coercable` with rules could be used to
coerce to the target type:
```rust
pub enum TypeSignature {
...
Coercible(Vec<Coercion>),
...
}
```
Where `Coercion` looks like
```rust
struct Coercion {
desired_type: TypeSignatureClass,
allowed_casts: ... // also includes an option for User Defined?
}
```
🤔
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