Information schema should use `return_field_from_args`

[Jefffrey]

datafusion/datafusion/catalog/src/information_schema.rs

Lines 424 to 428 in 3ea21aa

	// only handle the function which implemented [`ScalarUDFImpl::return_type`] method
	let return_type = udf
	.return_type(&arg_types)
	.map(|t| remove_native_type_prefix(&NativeType::from(t)))
	.ok();

datafusion/datafusion/catalog/src/information_schema.rs

Lines 450 to 454 in 3ea21aa

	// only handle the function which implemented [`ScalarUDFImpl::return_type`] method
	let return_type = udaf
	.return_type(&arg_types)
	.ok()
	.map(|t| remove_native_type_prefix(&NativeType::from(t)));

These should be using return_field_from_args as some UDFs/UDAFs/UDWFs implement that instead of return_type, especially since the default implementation of return_field_from_args already delegates to return_type

[Phaneendra293]

Hello, I’m new to this codebase and trying to understand this issue.

From my understanding, the suggestion is to prefer return_field_from_args
over return_type so that UDF/UDAF/UDTF schemas are handled consistently.

Could you please confirm if the intended fix is to update the information
schema functions to derive the return field from arguments instead of relying
on return_type?
’d like to take a look at this issue.

I plan to explore replacing usages of return_type with
return_field_from_args in the information schema logic.
Please let me know if this aligns with the expected approach.

[kumarUjjawal]

Hi @Phaneendra293 Thank you for your interest in this. You can take a look at this PR for reference #19275

[Jefffrey]

Could you please confirm if the intended fix is to update the information
schema functions to derive the return field from arguments instead of relying
on return_type?

Yes

[Jefffrey]

As part of this issue we should also fix date_trunc:

datafusion/datafusion/functions/src/datetime/date_trunc.rs

Lines 226 to 248 in 4ed808a

	// keep return_type implementation for information schema generation
	fn return_type(&self, arg_types: &[DataType]) -> Result<DataType> {
	if arg_types[1].is_null() {
	Ok(Timestamp(Nanosecond, None))
	} else {
	Ok(arg_types[1].clone())
	}
	}
	fn return_field_from_args(&self, args: ReturnFieldArgs) -> Result<FieldRef> {
	let data_types = args
	.arg_fields
	.iter()
	.map(|f| f.data_type())
	.cloned()
	.collect::<Vec<_>>();
	let return_type = self.return_type(&data_types)?;
	Ok(Arc::new(Field::new(
	self.name(),
	return_type,
	args.arg_fields[1].is_nullable(),
	)))
	}

• return_type should just return internal error and only implement return_field_from_args like other UDFs which implement return_field_from_args

[AndreaBozzo]

take