Hi everyone,

I've created database link in Oracle (11.2.0.4) over postgresql96-odbc driver to PostgreSQL (9.6) database.

DML commands work good. But I cannot call PG function over dblink.

Here is function on PG:

CREATE FUNCTION ADD(integer, integer) RETURNS integer
    AS 'select $1 + $2;'
    LANGUAGE SQL
    IMMUTABLE
    RETURNS NULL ON NULL INPUT;

and i'm trying call that function from Oracle:

SQL> SELECT "add"@pglink(2,3) FROM dual;
SELECT "add"@pglink(2,3) FROM dual
       *
ERROR at line 1:
ORA-00904: "add": invalid identifier

What is my problem? Isn't my syntax correct or anything else?

Sorry for english. I'm fully understand russian, don't hesitate to answer in your own language.
Thanks in advance.