ANALYZE shows r_rows=0

create table t1(a int);

insert into t1 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);

create table t2 (a int, key(a));

insert into t2 values (0),(1);

analyze select * from t1 straight_join t2 force index(a) where t2.a=t1.a;

id     select_type     table   type    possible_keys   key     key_len ref     rows    r_rows  filtered        r_filtered      Extra

1      SIMPLE  t1      ALL     NULL    NULL    NULL    NULL    10      10      100.00  100.00  Using where

1      SIMPLE  t2      ref     a       a       5       test.t1.a       2       0       100.00  100.00  Using index