BUG #11283: PostgreSQL bug? function's variable type cached not flushed within session when the type altered.

The following bug has been logged on the website:

Bug reference:      11283
Logged by:          digoal
Email address:      digoal@126.com
PostgreSQL version: 9.3.4
Operating system:   CentOS 6.5 x64
Description:

PostgreSQL bug? function's variable type cached not flushed within session
when the type altered.
see my test :
create table public.t (
  c1 int primary key,
  c2 text,
  crt_time timestamp
);

CREATE TABLE public.undo_t (
  id serial8 primary key,
  xid int8,
  relid oid,
  table_schema text,
  table_name text,
  when_tg text,
  level text,
  op text,
  encoding name,
  old_rec public.t,
  new_rec public.t,
  crt_time timestamp without time zone DEFAULT now(),
  username text,
  client_addr inet,
  client_port int
);


CREATE OR REPLACE FUNCTION public.undo_t_trace()
RETURNS trigger
LANGUAGE plpgsql
AS $BODY$
DECLARE
  v_new_rec public.t;  -- type cached in session, don't modified when table
t altered. must reopen an session.
  v_old_rec public.t;  -- type cached in session, don't modified when table
t altered. must reopen an session.
  v_username text := session_user;
  v_client_addr inet := inet_client_addr();
  v_client_port int := inet_client_port();
  v_xid bigint := txid_current();
  v_encoding name := pg_client_encoding();
BEGIN
  case TG_OP
  when 'DELETE' then
    v_old_rec := OLD;
    insert into public.undo_t (xid, relid, table_schema, table_name,
when_tg, level, op, encoding, old_rec, username, client_addr, client_port)
      values (v_xid, tg_relid, tg_table_schema, tg_table_name, tg_when,
tg_level, tg_op, v_encoding, v_old_rec, v_username, v_client_addr,
v_client_port);
  when 'INSERT' then
    raise notice '%', NEW;  -- OK
    v_new_rec := NEW;
    raise notice '%', v_new_rec;  -- use cached type. not OK.
    insert into public.undo_t (xid, relid, table_schema, table_name,
when_tg, level, op, encoding, new_rec, username, client_addr, client_port)
      values (v_xid, tg_relid, tg_table_schema, tg_table_name, tg_when,
tg_level, tg_op, v_encoding, v_new_rec, v_username, v_client_addr,
v_client_port);
  when 'UPDATE' then
    v_old_rec := OLD;
    v_new_rec := NEW;
    insert into public.undo_t (xid, relid, table_schema, table_name,
when_tg, level, op, encoding, old_rec, new_rec, username, client_addr,
client_port)
      values (v_xid, tg_relid, tg_table_schema, tg_table_name, tg_when,
tg_level, tg_op, v_encoding, v_old_rec, v_new_rec, v_username,
v_client_addr, v_client_port);
    when 'TRUNCATE' then
    insert into public.undo_t (xid, relid, table_schema, table_name,
when_tg, level, op, encoding, old_rec, username, client_addr, client_port)
      select v_xid, tg_relid, tg_table_schema, tg_table_name, tg_when,
tg_level, tg_op, v_encoding, t, v_username, v_client_addr, v_client_port
from public.t;
  else
    return null;
  end case;
    RETURN null;
END;
$BODY$ strict volatile;


CREATE TRIGGER tg1 AFTER DELETE or INSERT or UPDATE ON public.t FOR EACH ROW
EXECUTE PROCEDURE undo_t_trace();
CREATE TRIGGER tg2 BEFORE TRUNCATE ON public.t FOR EACH STATEMENT EXECUTE
PROCEDURE undo_t_trace();



insert into public.t values (1,'test',now());
insert into public.t values (2,'test',now());



postgres=# select * from public.t;
 c1 |  c2  |          crt_time
----+------+----------------------------
  1 | test | 2014-08-28 16:14:34.548555
  2 | test | 2014-08-28 16:14:35.194634
(2 rows)

postgres=# select new_rec from public.undo_t;
                new_rec
---------------------------------------
 (1,test,"2014-08-28 16:14:34.548555")
 (2,test,"2014-08-28 16:14:35.194634")
(2 rows)



postgres=# alter table public.t add column c3 int;
ALTER TABLE

postgres=# insert into public.t values (3,'test',now(),1);
NOTICE:  (3,test,"2014-08-28 16:15:58.394688",1)
NOTICE:  (3,test,"2014-08-28 16:15:58.394688",)
INSERT 0 1
postgres=# select * from public.t;
 c1 |  c2  |          crt_time          | c3
----+------+----------------------------+----
  1 | test | 2014-08-28 16:14:34.548555 |
  2 | test | 2014-08-28 16:14:35.194634 |
  3 | test | 2014-08-28 16:15:58.394688 |  1
(3 rows)

postgres=# select new_rec from public.undo_t;
                new_rec
----------------------------------------
 (1,test,"2014-08-28 16:14:34.548555",)
 (2,test,"2014-08-28 16:14:35.194634",)
 (3,test,"2014-08-28 16:15:58.394688",)
(3 rows)


postgres=# \q
postgres@192_168_173_203-> psql
psql (9.3.4)
Type "help" for help.
postgres=# select new_rec from public.undo_t;
                new_rec
----------------------------------------
 (1,test,"2014-08-28 16:14:34.548555",)
 (2,test,"2014-08-28 16:14:35.194634",)
 (3,test,"2014-08-28 16:15:58.394688",)
(3 rows)

postgres=# insert into public.t values (4,'test',now(),1);
NOTICE:  (4,test,"2014-08-28 16:16:45.857712",1)
NOTICE:  (4,test,"2014-08-28 16:16:45.857712",1)
INSERT 0 1
postgres=# select new_rec from public.undo_t;
                 new_rec
-----------------------------------------
 (1,test,"2014-08-28 16:14:34.548555",)
 (2,test,"2014-08-28 16:14:35.194634",)
 (3,test,"2014-08-28 16:15:58.394688",)
 (4,test,"2014-08-28 16:16:45.857712",1)
(4 rows)

postgres=# alter table t drop column c2;
ALTER TABLE
postgres=# \set VERBOSITY verbose


postgres=# insert into public.t values (5,now(),1);
NOTICE:  00000: (5,"2014-08-28 16:17:20.078688",1)
LOCATION:  exec_stmt_raise, pl_exec.c:3041
ERROR:  22007: invalid input syntax for type timestamp: "1"
CONTEXT:  PL/pgSQL function undo_t_trace() line 18 at assignment
LOCATION:  DateTimeParseError, datetime.c:3567