OceanBase大小账号导致执行计划突变验证

一：创建测试数据

create table t1 as select * from dba_objects;
update t1 set object_id=1 where rownum=1;
obclient> select object_id,count(*) from tbcs.t1 group by object_id;
+------+----------+
| ID | COUNT(*) |
+------+----------+
| 1 | 786432 |
| 2 | 1 |
+------+----------+
2 rows in set (0.67 sec)

二：执行计划突变测试验证
实验1 --第一次传参为大账号

obclient> set @v1=1;
Query OK, 0 rows affected (0.00 sec)

obclient> select count(owner) from t1 where object_id=@v1;
+--------------+
| COUNT(OWNER) |
+--------------+
| 695295 |
+--------------+
1 row in set (0.57 sec)

obclient> show trace;
+-------+----------------------+------+
| TITLE | KEYVALUE | TIME |
+-------+----------------------+------+
| NULL | PHY_SCALAR_AGGREGATE | NULL |
| T1 | PHY_TABLE_SCAN | NULL |
+-------+----------------------+------+
2 rows in set (0.01 sec)

obclient> set @v1=2;
Query OK, 0 rows affected (0.00 sec)

obclient> select count(owner) from t1 where object_id=@v1;
+--------------+
| COUNT(OWNER) |
+--------------+
| 1 |
+--------------+
1 row in set (0.00 sec)

obclient> show trace;
+-------+----------------------+------+
| TITLE | KEYVALUE | TIME |
+-------+----------------------+------+
| NULL | PHY_SCALAR_AGGREGATE | NULL |
| T1 | PHY_TABLE_SCAN | NULL |
+-------+----------------------+------+
2 rows in set (0.00 sec)

实验二：第二次传参为小账号

obclient> set @v1=2;
Query OK, 0 rows affected (0.00 sec)

obclient> select count(owner) from t1 where id=@v1;
ORA-00904: invalid identifier 'ID' in 'where clause'
obclient> select count(owner) from t1 where object_id=@v1;
+--------------+
| COUNT(OWNER) |
+--------------+
| 1 |
+--------------+
1 row in set (0.00 sec)

obclient> show trace;
+---------------+----------------------+------+
| TITLE | KEYVALUE | TIME |
+---------------+----------------------+------+
| NULL | PHY_SCALAR_AGGREGATE | NULL |
| T1(IDX_T1_ID) | PHY_TABLE_SCAN | NULL |
+---------------+----------------------+------+
2 rows in set (0.01 sec)

obclient> set @v1=1;
Query OK, 0 rows affected (0.00 sec)

obclient> select count(owner) from t1 where object_id=@v1;
+--------------+
| COUNT(OWNER) |
+--------------+
| 695295 |
+--------------+
1 row in set (2.29 sec)

obclient> show trace;
+---------------+----------------------+------+
| TITLE | KEYVALUE | TIME |
+---------------+----------------------+------+
| NULL | PHY_SCALAR_AGGREGATE | NULL |
| T1(IDX_T1_ID) | PHY_TABLE_SCAN | NULL |
+---------------+----------------------+------+