BUG #10155: BUG? Cann't remove new generated tuples after repeatable read transaction start.

The following bug has been logged on the website:

Bug reference:      10155
Logged by:          digoal.zhou
Email address:      digoal@126.com
PostgreSQL version: 9.3.3
Operating system:   CentOS 6.4 x64
Description:

SESSION A :
digoal=# begin isolation level repeatable read;
BEGIN
digoal=# \dt
                 List of relations
 Schema |         Name          | Type  |  Owner
--------+-----------------------+-------+----------
 public | stat_pg_stat_database | table | postgres
 public | tbl_cost_align        | table | postgres
 public | test                  | table | postgres
 public | ttt                   | table | postgres
 public | tttt                  | table | postgres
 public | ttttt                 | table | postgres
(6 rows)

SESSION B :
digoal=# create table t as select * from pg_class;
SELECT 306

SESSION A :
no table t in it , A cann't see the t metadata in pg_class and pg_attr and
so on.
digoal=# \dt
                 List of relations
 Schema |         Name          | Type  |  Owner
--------+-----------------------+-------+----------
 public | stat_pg_stat_database | table | postgres
 public | tbl_cost_align        | table | postgres
 public | test                  | table | postgres
 public | ttt                   | table | postgres
 public | tttt                  | table | postgres
 public | ttttt                 | table | postgres
(6 rows)

SESSION B :
but B cann't reclaim rows from table t.
why?
i think postgresql cann't reclaim tuples already exists before repeatable
read transaction start, why this case t's tuples after session a and cann't
reclaim.


digoal=# delete from t;
DELETE 306
digoal=# vacuum freeze verbose t;
INFO:  vacuuming "public.t"
INFO:  "t": found 0 removable, 306 nonremovable row versions in 2 out of 2
pages
DETAIL:  306 dead row versions cannot be removed yet.
There were 0 unused item pointers.
0 pages are entirely empty.
CPU 0.00s/0.00u sec elapsed 0.00 sec.
INFO:  vacuuming "pg_toast.pg_toast_33578"
INFO:  index "pg_toast_33578_index" now contains 0 row versions in 1 pages
DETAIL:  0 index row versions were removed.
0 index pages have been deleted, 0 are currently reusable.
CPU 0.00s/0.00u sec elapsed 0.00 sec.
INFO:  "pg_toast_33578": found 0 removable, 0 nonremovable row versions in 0
out of 0 pages
DETAIL:  0 dead row versions cannot be removed yet.
There were 0 unused item pointers.
0 pages are entirely empty.
CPU 0.00s/0.00u sec elapsed 0.00 sec.
VACUUM


when SESSION end;
session b can reclaim these dead tuple.