sql cli with hive catalog cannot create function using user classes from jar which specified by -j option

with flink version 1.12.0(versions before also affected)

I started a sql cli  with a hive catalog and specified a user jar file with -j option like this:

bin/sql-client.sh embedded -j /Users/akis/Desktop/flink-func/myfunc.jar

when i tried to create a custom function using class from myfunc.jar，cli reported ClassNotFoundException.

Flink SQL> use catalog myhive;

Flink SQL> create function myfunc1 as 'me.aki.flink.flinkudf.MyFunc';
[ERROR] Could not execute SQL statement. Reason:
java.lang.ClassNotFoundException: me.aki.flink.flinkudf.MyFunc

me.aki.flink.flinkudf.MyFunc is the identifier of udf，which defined like this

package me.aki.flink.flinkudf;

import org.apache.flink.table.functions.ScalarFunction;

public class MyFunc extends ScalarFunction {
    public String eval(String s) {
        return "myfunc_" + s;
    }
}

after walking through the related code, I believe this is a bug caused by wrong classloader

when using a hive catalog, flink will use  CatalogFunctionImpl  to wrap the function。 The

isGeneric() methed  uses Class.forName(String clazzName) which will use a current classloader(classloader loads flink/lib) to determine the class。

however with -j option, user jar is set to the ExecutionContext and loaded by another userClassLoader

and the fix can be easy to pass a classloader to the Class.forName method.

ClassLoader cl = Thread.currentThread().getContextClassLoader();
Class c = Class.forName(className, true, cl);

after do such fix and build a new flink dist，create function behaves right

Flink SQL> select myfunc1('1');

// output
     EXPR$0
     myfunc_1