Jefffrey commented on PR #19308:
URL: https://github.com/apache/datafusion/pull/19308#issuecomment-3665334719
One thing I'm not understanding, is that this PR seems to imply all
arguments are now optional and any can be skipped, filling in skipped arguments
with scalar `NULL`; this means it is up to the UDFs themselves to check which
arguments were provided (and define which are required), and assume that any
scalar `NULL`s mean the argument was missing (even if the caller passed in a
scalar `NULL` themself), correct?
For example if we had a UDF like so:
```
name: custom_udf
signatures:
- prefix: string, length: i64
- prefix: string, suffix: string, length: i64
```
Technically here `suffix` is optional, and when calling the function if we
call it two 2 arguments (string & i64) then we'd know that only 2 arguments
were provided and the implementation of the UDF can branch based on that.
However if we call with named arguments for `prefix` and `length` but still
omit `suffix`:
```sql
custom_udf(prefix => 'a', length => 1)
```
We'd always have 3 arguments provided because `suffix` gets filled with null.
- Technically I think this code wouldn't work on current main anyway, now
that I think of it; though it would just cause an error
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