Incorrect #rows computations in DuplicateWeedout strategy choice

create table t1(a int, b int);

insert into t1 select seq,seq from seq_0_to_3;

create table t2 (p int, a int);

insert into t2 select seq,seq from seq_1_to_10;

insert into t2 select seq,seq from seq_10_to_100;

explain extended select * from t1 where a in (select p from t2);

+------+-------------+-------+------+---------------+------+---------+------+------+----------+---------------------------------------------------------------------------------+

| id   | select_type | table | type | possible_keys | key  | key_len | ref  | rows | filtered | Extra                                                                           |

+------+-------------+-------+------+---------------+------+---------+------+------+----------+---------------------------------------------------------------------------------+

|    1 | PRIMARY     | t1    | ALL  | NULL          | NULL | NULL    | NULL | 4    |   100.00 |                                                                                 |

|    1 | PRIMARY     | t2    | ALL  | NULL          | NULL | NULL    | NULL | 101  |   100.00 | Using where; Start temporary; End temporary; Using join buffer (flat, BNL join) |

+------+-------------+-------+------+---------------+------+---------+------+------+----------+---------------------------------------------------------------------------------+

(gdb) p first_tab

  $12 = 1

(gdb) p join->positions[first_tab].prefix_record_count

  $13 = 404

(gdb) print sj_outer_fanout

  $15 = 1

(gdb) print sj_inner_fanout

  $16 = 101

      double full_lookup_cost=

               COST_MULT(join->positions[first_tab].prefix_record_count,

                         COST_MULT(sj_outer_fanout,

                                   sj_inner_fanout * one_lookup_cost));