Wrong result with small join_buffer_space_limit and hash join

set join_cache_level=4;

set join_buffer_space_limit=4000;

create table t1 (pk varchar(512), a varchar(512));

insert into t1 select seq, seq from seq_1_to_10;

create table t2 (pk varchar(512), a varchar(512));

insert into t2 select seq, seq from seq_1_to_10;

create table t3 (pk varchar(512), a varchar(512));

insert into t3 select seq, seq from seq_1_to_5;

create table t4 (pk varchar(512), a varchar(512), key(a));

insert into t4 select seq, seq from seq_1_to_5;

select count(*) from t1,t2,t3 left join t4 on t3.pk=t4.a where t1.a=t2.pk and t2.pk=t3.a;

MariaDB [test]> select count(*) from t1,t2,t3 left join t4 on t3.pk=t4.a where t1.a=t2.pk and t2.pk=t3.a;

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

| count(*) |

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

|       25 |

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

MariaDB [test]> set join_buffer_space_limit=10000;

MariaDB [test]> select count(*) from t1,t2,t3 left join t4 on t3.pk=t4.a where t1.a=t2.pk and t2.pk=t3.a;

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

| count(*) |

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

|        5 |

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