How to access PostgreSQL Functions from Oracle through DBLink?

I'm having two DB server (PostgreSQL, Oracle). I'm able to access the table in PostgreSQL from Oracle through DB-Link. I've use the below query to access the table. select "Cust_Id", "Mobile_No" from "schema_name"."tablename"@Dblink where "cust_id" = '123456789'; As same as I'm trying to access the function in PostgreSQL from Oracle server through DBLink. But I can't access it. I've used below query select "Cust_id" from "schema_name"."function_name"@DbLink('123456789'); The function will return the mobileno and cust_id in table type. I'm getting error like. > SQL Command not properly ended Pls help on this issue. Thnx in advance.