执行了很多sql，为什么视图oceanbase.gv$ob_plan_cache_plan_explain中没有数据中一条数据都没有呢，plan cache已经打开了呀。
obclient(root@obmysql)[oceanbase]> show variables like ‘ob_plan_cache_percentage’;
±-------------------------±------+
| Variable_name | Value |
±-------------------------±------+
| ob_plan_cache_percentage | 5 |
±-------------------------±------+
1 row in set (0.003 sec)
obclient(root@obmysql)[oceanbase]> show variables like ‘ob_enable_plan_cache’;
±---------------------±------+
| Variable_name | Value |
±---------------------±------+
| ob_enable_plan_cache | ON |
±---------------------±------+
1 row in set (0.001 sec)