jkosh44 commented on code in PR #15237:
URL: https://github.com/apache/datafusion/pull/15237#discussion_r1996444071
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docs/source/library-user-guide/upgrading.md:
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@@ -212,4 +212,79 @@ To include special characters (such as newlines via `\n`)
you can use an `E` lit
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```
+### More expressive scalar array function signatures
+
+Datafusion 46 has changed the way scalar array function signatures are
+declared. Previously, functions needed to select from a list of predefined
+signatures within the `ArrayFunctionSignature` enum. Now the signatures
+can be defined via a `Vector` of psuedo-types, which each correspond to a
+single argument. Those psuedo-types are the variants of the
+`ArrayFunctionArgument` enum and are as follows:
+
+ - `Array`: An argument of type List/LargeList/FixedSizeList. All Array
+ arguments must be coercible to the same type.
+ - `Element`: An argument that is coercible to the inner type of the `Array`
+ arguments.
+ - `Index`: An `Int64` argument.
+
+Each of the old variants can be converted to the new format as follows:
+
+`TypeSignature::ArraySignature(ArrayFunctionSignature::ArrayAndElement)`:
+```rust
+TypeSignature::ArraySignature(ArrayFunctionSignature::Array {
+ arguments: vec![ArrayFunctionArgument::Array,
ArrayFunctionArgument::Element],
+ array_coercion: Some(ListCoercion::FixedSizedListToList),
+});
+```
+
+`TypeSignature::ArraySignature(ArrayFunctionSignature::ElementAndArray)`:
+```rust
+TypeSignature::ArraySignature(ArrayFunctionSignature::Array {
+ arguments: vec![ArrayFunctionArgument::Element,
ArrayFunctionArgument::Array],
+ array_coercion: Some(ListCoercion::FixedSizedListToList),
+})
+```
+
+`TypeSignature::ArraySignature(ArrayFunctionSignature::ArrayAndIndex)`:
+```rust
+TypeSignature::ArraySignature(ArrayFunctionSignature::Array {
+ arguments: vec![ArrayFunctionArgument::Array,
ArrayFunctionArgument::Index],
+ array_coercion: None,
+})
+```
+
+`TypeSignature::ArraySignature(ArrayFunctionSignature::ArrayAndElementAndOptionalIndex)`:
+```rust
+TypeSignature::OneOf(vec![
+ TypeSignature::ArraySignature(ArrayFunctionSignature::Array {
+ arguments: vec![ArrayFunctionArgument::Array,
ArrayFunctionArgument::Element],
+ array_coercion: None,
+ }),
+ TypeSignature::ArraySignature(ArrayFunctionSignature::Array {
+ arguments: vec![
+ ArrayFunctionArgument::Array,
+ ArrayFunctionArgument::Element,
+ ArrayFunctionArgument::Index,
+ ],
+ array_coercion: None,
+ }),
+])
+```
+
+`TypeSignature::ArraySignature(ArrayFunctionSignature::Array)`:
+```rust
+TypeSignature::ArraySignature(ArrayFunctionSignature::Array {
+ arguments: vec![ArrayFunctionArgument::Array],
+ array_coercion: None,
+})
+```
Review Comment:
I am not at all a fan of how I formatted this, but I couldn't think of
anything better. So I am very open to suggestions.
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