how to create duplicate role of a user in postgres

I need a new user but it should be granted all those privileges that the other existing user/role has.

e.g.

User A has SELECT privileges on Table1
User A has EXECUTE privileges on Table2
...

If a new User B is created, I need the same privileges as,

User B has SELECT privileges on Table1
User B has EXECUTE privileges on Table2
...

Dont ask why :/

Actually User A has custom privileges on different tables, schemas, and functions; so its very tedious and lengthy process to manually grant permissions to the new user. Any help would be good.

Solution

I had to write the pgpsql code to loop through the privileges of User A and grant it to User B. It was done without any problem.

create or replace function update_user_privileges() returns text as
$$
declare

       info record;
       str text;

begin
       /*Grant privileges to user B the same as with user A for a given table schema*/
      str:=''; 
      FOR info IN 
          select * from information_schema.table_privileges where table_schema='public' and grantee = 'A'   
      LOOP 
          /*append the tables' name, for which we are assigning privileges from user A to B*/
          str:= str  ||info.table_name || ',';

         /*this is the main statement to grant any privilege*/
         execute 'GRANT '|| info.privilege_type ||' on table public.'|| info.table_name || ' to B';

      END LOOP;

  return str;
end

$$ language 'plpgsql';

Usage: Copy/paste this code to crate this function and then do

select update_user_privileges();

**You have to adapt it for your table-schema and table-names. Hope it helps anyone