optimizer跟踪没有生成跟踪信息？

[tangren]

为何跟踪没有生成？

mysql> set optimizer_trace="enabled=on";
Query OK, 0 rows affected (0.00 sec)

mysql> show variables like '%optimizer_trace%';
+------------------------------+----------------------------------------------------------------------------+
| Variable_name | Value |
+------------------------------+----------------------------------------------------------------------------+
| optimizer_trace | enabled=on,one_line=off |
| optimizer_trace_features | greedy_search=on,range_optimizer=on,dynamic_range=on,repeated_subselect=on |
| optimizer_trace_limit | 1 |
| optimizer_trace_max_mem_size | 16384 |
| optimizer_trace_offset | -1 |
+------------------------------+----------------------------------------------------------------------------+
5 rows in set, 1 warning (0.00 sec)

mysql> select * from t1 where id=getnum();
+----+-------+---------------------+
| id | phone | crttime |
+----+-------+---------------------+
| 1 | 11 | 2020-03-08 10:00:00 |
+----+-------+---------------------+
1 row in set (0.03 sec)


mysql> SELECT * FROM information_schema.OPTIMIZER_TRACE;
+-------------+----------------------+-----------------------------------+-------------------------+
| QUERY | TRACE | MISSING_BYTES_BEYOND_MAX_MEM_SIZE | INSUFFICIENT_PRIVILEGES |
+-------------+----------------------+-----------------------------------+-------------------------+
| freturn 3 1 | {
"steps": [
]
} | 0 | 0 |
+-------------+----------------------+-----------------------------------+-------------------------+
1 row in set (0.00 sec)

[带我飞的云]

如果前面有开启 optimizer_trace 要先关闭

[tangren]

optimizer_trace默认就是关闭的，应该不是这个原因

[毕竟我很菜]

10年了。。。