mysql> create table t(id int primary key,age int);
Query OK, 0 rows affected (1.66 sec)

mysql>
mysql> alter table t add index idx_age(age);
Query OK, 0 rows affected (0.17 sec)
Records: 0 Duplicates: 0 Warnings: 0

mysql> insert into t values(1,1),(2,3),(3,4),(4,4),(5,7),(6,7),(7,10),(8,11);
Query OK, 8 rows affected (0.17 sec)
Records: 8 Duplicates: 0 Warnings: 0

---sess 1

mysql> begin;
Query OK, 0 rows affected (0.00 sec)

mysql> insert into t select 9,3;
Query OK, 1 row affected (0.00 sec)
Records: 1 Duplicates: 0 Warnings: 0

sess 2

mysql> select * from performance_schema.data_locks\G;
*************************** 1. row ***************************
ENGINE: INNODB
ENGINE_LOCK_ID: 139831828299216:1158:139831720086024
ENGINE_TRANSACTION_ID: 14900
THREAD_ID: 50
EVENT_ID: 188
OBJECT_SCHEMA: test
OBJECT_NAME: t
PARTITION_NAME: NULL
SUBPARTITION_NAME: NULL
INDEX_NAME: NULL
OBJECT_INSTANCE_BEGIN: 139831720086024
LOCK_TYPE: TABLE
LOCK_MODE: IX
LOCK_STATUS: GRANTED
LOCK_DATA: NULL

请问LOCK_DATA: NULL 为啥是null，不应该有数据吗？