HIVE-24997. HPL/SQL udf doesn't work in tez container mode (amagyar)

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HPLSQL supports stored function calls from HiveQL selects:

For example:

create function hello(s string) returns string;
begin
  return 'hello ' || s;
end;

The above stored function can be used in a select:

select hello(name) from employees;

HPLSQL translates this to a UDF call.

SELECT hplsql('hello(:1)', name) FROM users;

The hplsql UDF is going to call the hplsql interpreter to evaluate the hello function. The earlier implementation used to look up the interpreter from the session state. But this only works if the evaluation happens in compile time and the UDF is running inside the HS2 process. This is not true for general therefore the UDF should instantiate a new interpreter and use that to eval the function call.

[zeroflag]

cc: @mustafaiman

[mustafaiman]

👍