viirya opened a new issue, #9892:
URL: https://github.com/apache/arrow-datafusion/issues/9892

   ### Is your feature request related to a problem or challenge?
   
   Currently more and more built-in scalar functions are moved to `functions` 
modules, e.g. https://github.com/apache/arrow-datafusion/pull/9435. It avoids 
using a long enum of all built-in scalar functions which is hard to maintain. 
But for Comet, we rely the ability to create a physical scalar expression from 
string (e.g., `datepart`).
   
   Previously it is easy and just calls `BuiltinScalarFunction::from_str` to 
get `BuiltinScalarFunction`. But now I don't see such convenient function to do 
that.
   
   `FunctionRegistry` provides `udf` which can return a reference to 
`ScalarUDF`. But it requires these UDFs must be registered. As we don't know 
what UDFs will be used, we need to register all built-in UDFs in the registry. 
The flaw is, it will create `ScalarUDF`s for all built-in UDFs even they are 
not actually used in the queries.
   
   I think we still need an approach that can simply create a physical scalar 
expression in `functions` modules from string. So we can create corresponding 
`ScalarUDF` on demand.
   
   
   
   
   
   
   
   
   
   
   
   ### Describe the solution you'd like
   
   _No response_
   
   ### Describe alternatives you've considered
   
   _No response_
   
   ### Additional context
   
   _No response_


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