Similarities and differences between the defined identity execution function authid determiner and PostgreSQL in Oracle

Oracle Behavior

Oracle The function in can define the execution function body , Which user's permissions are used ：

［AUTHID { CURRENT_USER|DEFINER}]

CURRENT_USER The function body has been executed as the current user 
DEFINER The identity of the defined person executes the function body 

CASE1： For example, the following function will use the current user to execute the function body , If the current user is on tbl1 Read permission can be successfully executed .

CREATE OR REPLACE PROCEDURE TEST_P AUTHID CURRENT_USER IS
BEGIN
    EXECUTE IMMEDIATE 'select * from tbl1';
END TEST_P;

CASE2： The following function will use the user who defines the function to execute the function body , If the user who defines the function is right tbl1 Read permission can be successfully executed .

CREATE OR REPLACE PROCEDURE TEST_P AUTHID DEFINER IS
BEGIN
    EXECUTE IMMEDIATE 'select * from tbl1';
END TEST_P;

PG Behavior

PG The execution function in is always executed with the permission of the current user , similar Oracle in AUTHID CURRENT_USER The concept of .

for example user1 Create table

drop table u1tbl;
create table u1tbl(i int);
insert into u1tbl values (123);

user2 Query without permission

postgres=> select * from u1tbl;
ERROR:  permission denied for table u1tbl

user1 Create a function

drop function f1();
CREATE OR REPLACE FUNCTION f1() RETURNS int AS $$
DECLARE
	id int;
BEGIN
	select i into id from u1tbl;
	return id;
END;
$$ LANGUAGE plpgsql;

user2 Execute function

postgres=> select f1();
ERROR:  permission denied for table u1tbl
CONTEXT:  SQL statement "select i         from u1tbl"
PL/pgSQL function f1() line 5 at SQL statement

so PG There is no such way to implement the defined identity .