Suspicious behaviour on applying XLOG_HEAP2_VISIBLE.

Hi all,

I faced suspicious behaviour on hot standby server related to visibility map.
The scenario is,

1. Create table and check internal of visibility map on master server.
postgres(1)=# create table hoge (col int);
CREATE TABLE
postgres(1)=# insert into hoge select generate_series(1,10);
INSERT 0 10
postgres(1)=# select * from pg_visibility('hoge');
 blkno | all_visible | all_frozen | pd_all_visible
-------+-------------+------------+----------------
     0 | f           | f          | f
(1 row)

2. Check internal of visibility map on standby server.
postgres(1)=# select * from pg_visibility('hoge');
 blkno | all_visible | all_frozen | pd_all_visible
-------+-------------+------------+----------------
     0 | f           | f          | f
(1 row)

3. Do VACUUM on master server.
postgres(1)=# vacuum hoge;
VACUUM
postgres(1)=# select * from pg_visibility('hoge');
 blkno | all_visible | all_frozen | pd_all_visible
-------+-------------+------------+----------------
     0 | t           | f          | t
(1 row)

4. Check internal of visibility map on standby server again.
** Note that the we use the connection we established at #2 again **
postgres(1)=# select * from pg_visibility('hoge');
 blkno | all_visible | all_frozen | pd_all_visible
-------+-------------+------------+----------------
     0 | f           | f          | t
(1 row)

Even on standby server, the result should be (t,f,t), but returned (f,f,t)
(XLOG_HEAP2_VISIBLE record actually has been reached to standby, and
has been surely  applied)

As a result of looked into code around the recvoery, ISTM that the
cause is related to relation cache clear.
In heap_xlog_visible, if the standby server receives WAL record then
relation cache is eventually cleared in vm_extend,  but If standby
server receives FPI then relation cache would not be cleared.
For example, after I applied attached patch to HEAD, (it might not be
right way but) this problem seems to be resolved.

Is this a bug? or not?

Regards,

--
Masahiko Sawada