BUG #15057: Issue with UNKNOW type when calling a PostgreSQL function from java code

The following bug has been logged on the website:

Bug reference: 15057
Logged by: Praveen Kumar
Email address: praveenkumar52028(at)gmail(dot)com
PostgreSQL version: 9.6.0
Operating system: Redhat Linux 6
Description:

Hi Guys,

We have recently migrated our oracle database to PostgreSQL database,and
migration went successfully.
We have used ORAFCE to provide backward compatibility.
But ,unfortunately we stuck with one issue in calling DECODE /TRUNC/or any
other user defined PostgreSQL functions

That is type UNKNOWN

If I try to call a function as below

select myFunction(1,'This is unknown type',90.01,'Again a unknown type
column');

It is raising an error like function myFunction(integer, unknown, double
precision, unknown) does not exist.

But in reality, I have this function like myFunction(integer,text,double
precision,text)

I have gone through all PostgreSQL documents and mail threads but couldn't
find any accurate solution.
Kindly provide an immediate workaround or a permanent solution.

FYI - I have tried latest PostgreSQL version(PostgreSQL 10) Still no use of
it

select 'hello' return text type

select pg_typeof('hello') returns unknown type

Please help out to fix this.

Thanks,
Praveen