mysql> show indexes from tree;
+-------+------------+------------+--------------+---------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| Table | Non_unique | Key_name   | Seq_in_index | Column_name   | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
+-------+------------+------------+--------------+---------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| tree  |          0 | PRIMARY    |            1 | child         | A         |         133 |     NULL | NULL   |      | BTREE      |         |               |
| tree  |          0 | PRIMARY    |            2 | parent        | A         |         133 |     NULL | NULL   |      | BTREE      |         |               |
| tree  |          0 | PRIMARY    |            3 | relation_type | A         |         133 |     NULL | NULL   |      | BTREE      |         |               |
| tree  |          1 | idx_tree   |            1 | child         | A         |         133 |     NULL | NULL   |      | BTREE      |         |               |
| tree  |          1 | idx_tree   |            2 | parent        | A         |         133 |     NULL | NULL   |      | BTREE      |         |               |
| tree  |          1 | idx_tree   |            3 | relation_type | A         |         133 |     NULL | NULL   |      | BTREE      |         |               |
| tree  |          1 | idx_tree_1 |            1 | parent        | A         |          66 |     NULL | NULL   |      | BTREE      |         |               |
| tree  |          1 | idx_tree_2 |            1 | child         | A         |         133 |     NULL | NULL   |      | BTREE      |         |               |
| tree  |          1 | idx_tree_3 |            1 | relation_type | A         |          14 |     NULL | NULL   |      | BTREE      |         |               |
| tree  |          1 | idx_tree_4 |            1 | parent        | A         |          66 |     NULL | NULL   |      | BTREE      |         |               |
| tree  |          1 | idx_tree_4 |            2 | child         | A         |         133 |     NULL | NULL   |      | BTREE      |         |               |
| tree  |          1 | idx_tree_4 |            3 | relation_type | A         |         133 |     NULL | NULL   |      | BTREE      |         |               |
| tree  |          1 | idx_tree_5 |            1 | parent        | A         |          66 |     NULL | NULL   |      | BTREE      |         |               |
| tree  |          1 | idx_tree_5 |            2 | relation_type | A         |          66 |     NULL | NULL   |      | BTREE      |         |               |
| tree  |          1 | idx_tree_6 |            1 | child         | A         |         133 |     NULL | NULL   |      | BTREE      |         |               |
| tree  |          1 | idx_tree_6 |            2 | relation_type | A         |         133 |     NULL | NULL   |      | BTREE      |         |               |
| tree  |          1 | parent     |            1 | parent        | A         |          66 |     NULL | NULL   |      | BTREE      |         |               |
| tree  |          1 | child      |            1 | child         | A         |         133 |     NULL | NULL   |      | BTREE      |         |               |
+-------+------------+------------+--------------+---------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
18 rows in set (0.00 sec)