我正在使用带有非常基本查询的 AWS Aurora 数据库（MySQL 引擎）：
SELECT * FROM phones_table where phone_number = 98371381;
该phone_number列上的该表有一个索引：
mysql> show index from vaya_call_data_record;
+--------------+------------+--------------------------------+--------------+----------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
+--------------+------------+--------------------------------+--------------+----------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| phones_table | 0 | PRIMARY | 1 | id | A | 4415670 | NULL | NULL | | BTREE | | |
| phones_table | 1 | idx_phones_table_phone_number …