odd-explain-hash-no-jbuf

MariaDB [test]> explain SELECT SUM( l_partkey ) FROM region JOIN nation ON ( r_regionkey = n_regionkey ) LEFT JOIN supplier ON ( s_nationkey = n_nationkey ) JOIN partsupp ON ( s_suppkey = ps_suppkey ) RIGHT JOIN lineitem ON ( ps_partkey = l_partkey AND ps_suppkey = l_suppkey ) JOIN orders ON ( l_orderkey = o_orderkey ) WHERE o_comment IS NOT NULL OR n_comment IS NOT NULL AND ps_availqty = l_quantity\G
*************************** 1. row ***************************
           id: 1
  select_type: SIMPLE
        table: orders
         type: ALL
possible_keys: PRIMARY
          key: NULL
      key_len: NULL
          ref: NULL
         rows: 150
        Extra: 
*************************** 2. row ***************************
           id: 1
  select_type: SIMPLE
        table: lineitem
         type: hash_ALL
possible_keys: PRIMARY,i_l_orderkey,i_l_orderkey_quantity
          key: #hash#PRIMARY
      key_len: 4
          ref: test.orders.o_orderkey
         rows: 586
        Extra: Using join buffer (flat, BNLH join)
*************************** 3. row ***************************
           id: 1
  select_type: SIMPLE
        table: supplier
         type: hash_index
possible_keys: PRIMARY,i_s_nationkey
          key: #hash#PRIMARY:i_s_nationkey
      key_len: 4:5
          ref: test.lineitem.l_suppkey
         rows: 1
        Extra: Using where; Using index
*************************** 4. row ***************************
           id: 1
  select_type: SIMPLE
        table: nation
         type: hash_ALL
possible_keys: PRIMARY,i_n_regionkey
          key: #hash#PRIMARY
      key_len: 4
          ref: test.supplier.s_nationkey
         rows: 25
        Extra: Using where
*************************** 5. row ***************************
           id: 1
  select_type: SIMPLE
        table: partsupp
         type: hash_ALL
possible_keys: PRIMARY,i_ps_partkey,i_ps_suppkey
          key: #hash#PRIMARY
      key_len: 8
          ref: test.lineitem.l_partkey,test.lineitem.l_suppkey
         rows: 20
        Extra: Using where
*************************** 6. row ***************************
           id: 1
  select_type: SIMPLE
        table: region
         type: hash_ALL
possible_keys: PRIMARY
          key: #hash#PRIMARY
      key_len: 4
          ref: test.nation.n_regionkey
         rows: 5
        Extra: 
6 rows in set (0.007 sec)