unsupport to create a temporary|permanent function with the key word 'IF NOT EXISTS'.
I think it is necessary to support this key word in 'create [temporary] fucntion ...' clause,
I hava an application which has three steps as follow :
1. insert into table t1 as select id from t where ...
2. create function AA as ... using jar ...
3. insert into table t2 select AA(id) from t1
my application run succussfully first time and it will throw an exeception at step 2 when it run again. So, I think it is reasonable and friendly to user application.