数据库版本崖山23.5.1
SQL> select * from v$version;
BANNER VERSION_NUMBER
---------------------------------------------------------------- -----------------
Enterprise Edition Release 23.5.1.100 x86_64 23.5.1.100
1 row fetched.测试SQL
select *
from test02 t2
where t2.data_object_id =
(select max(data_object_id)
from test01 t3
where t3.object_id = t2.object_id)
and t2.owner = 'SCOTT';执行计划
SQL> select *
from test02 t2
where t2.data_object_id =
(select max(data_object_id)
from test01 t3
where t3.object_id = t2.object_id)
and t2.owner = 'SCOTT'; 2 3 4 5 6 7
Execution Plan
----------------------------------------------------------------
SQL hash value: 3493843295
Optimizer: ADOPT_C
+----+--------------------------------+----------------------+------------+----------+----------+-------------+----------+----------+----------+----------+--------------------------------+
| Id | Operation type | Name | Owner | E - Rows | A - Rows | Cost(%CPU) | A - Time | Loops | Memory | Disk | Partition info |
+----+--------------------------------+----------------------+------------+----------+----------+-------------+----------+----------+----------+----------+--------------------------------+
| 0 | SELECT STATEMENT | | | | 31| | 14233163| 32| 0| 0| |
| 1 | SUBQUERY | QUERY[1] | | | 86987| | 14097886| 173974| 0| 0| |
| 2 | AGGREGATE | | | 1| 86987| 5( 0)| 14069037| 173974| 0| 0| |
|* 3 | TABLE ACCESS BY INDEX ROWID | TEST01 | SCOTT | 145| | 5( 0)| | | | | |
|* 4 | INDEX RANGE SCAN | IDX_TEST01_OBJECT_ID | SCOTT | 446| 4696064| 1( 0)| 13655265| 4783051| 0| 0| |
|* 5 | TABLE ACCESS FULL | TEST02 | SCOTT | 1| 31| 238( 0)| 14233153| 32| 0| 0| |
+----+--------------------------------+----------------------+------------+----------+----------+-------------+----------+----------+----------+----------+--------------------------------+
Operation Information (identified by operation id):
---------------------------------------------------
1 - Subquery NDV info - NDV percentage: 0.000011, NDV Expression: ("T2"."OBJECT_ID"[OPTMZ-1])
3 - Predicate : filter("T3"."DATA_OBJECT_ID"[OPTMZ-1] IS NOT NULL)
4 - Predicate : access("T3"."OBJECT_ID" = "T2"."OBJECT_ID"[OPTMZ-1][OPTMZ-2])
5 - Predicate : filter("T2"."DATA_OBJECT_ID"[OPTMZ-1] = QUERY[1][OPTMZ-0] AND "T2"."OWNER"[OPTMZ-1] = 'SCOTT'[OPTMZ-0])
Statistics
----------------------------------------------------------------------------------------------------
0 physical reads
44795489 db block gets
0 consistent gets
0 redo size
0 recursive calls
0 bytes sent via SQL*Net to client
0 bytes received via SQL*Net from client
0 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
31 rows processed
0 bytes sent via PX
0 block received
34 rows fetched.
Elapsed: 00:00:14.238SQL耗时14秒，正常来说应该秒杀才对
改写(方法一)
SQL> select *
from (select *
from test02
where owner = 'SCOTT'
and rownum >= 1) t2
where t2.data_object_id =
(select max(data_object_id)
from test01 t3
where t3.object_id = t2.object_id); 2 3 4 5 6 7 8 9
Execution Plan
----------------------------------------------------------------
SQL hash value: 2360477481
Optimizer: ADOPT_C
+----+--------------------------------+----------------------+------------+----------+----------+-------------+----------+----------+----------+----------+--------------------------------+
| Id | Operation type | Name | Owner | E - Rows | A - Rows | Cost(%CPU) | A - Time | Loops | Memory | Disk | Partition info |
+----+--------------------------------+----------------------+------------+----------+----------+-------------+----------+----------+----------+----------+--------------------------------+
| 0 | SELECT STATEMENT | | | | 31| | 26400| 32| 0| 0| |
| 1 | SUBQUERY | QUERY[1] | | | 36| | 20842| 72| 0| 0| |
| 2 | AGGREGATE | | | 1| 36| 5( 0)| 20745| 72| 0| 0| |
|* 3 | TABLE ACCESS BY INDEX ROWID | TEST01 | SCOTT | 145| | 5( 0)| | | | | |
|* 4 | INDEX RANGE SCAN | IDX_TEST01_OBJECT_ID | SCOTT | 446| 15872| 1( 0)| 19480| 15908| 0| 0| |
|* 5 | VIEW | | | 12| 31| 223( 0)| 26398| 32| 0| 0| |
| 6 | COUNT | | | 12| 36| 216( 0)| 5418| 37| 0| 0| |
|* 7 | RESULT | | | 12| 36| 216( 0)| 5410| 37| 0| 0| |
|* 8 | TABLE ACCESS FULL | TEST02 | SCOTT | 36| 36| 216( 0)| 5390| 37| 0| 0| |
+----+--------------------------------+----------------------+------------+----------+----------+-------------+----------+----------+----------+----------+--------------------------------+
Operation Information (identified by operation id):
---------------------------------------------------
3 - Predicate : filter("T3"."DATA_OBJECT_ID"[OPTMZ-1] IS NOT NULL)
4 - Predicate : access("T3"."OBJECT_ID" = "TEST02"."OBJECT_ID"[OPTMZ-3][OPTMZ-2])
5 - Predicate : filter("TEST02"."DATA_OBJECT_ID"[OPTMZ-3] = QUERY[1][OPTMZ-0])
7 - Predicate : filter(ROWNUM[OPTMZ-0] >= 1[OPTMZ-0])
8 - Predicate : filter("TEST02"."OWNER"[OPTMZ-1] = 'SCOTT'[OPTMZ-0])
Statistics
----------------------------------------------------------------------------------------------------
0 physical reads
19859 db block gets
0 consistent gets
0 redo size
0 recursive calls
0 bytes sent via SQL*Net to client
0 bytes received via SQL*Net from client
0 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
31 rows processed
0 bytes sent via PX
0 block received
38 rows fetched.
Elapsed: 00:00:00.029改写(方法二)
SQL> select *
from (select t2.*,
(select max(data_object_id)
from test01 t3
where t3.object_id = t2.object_id) max_data_object_id
from test02 t2)
where data_object_id = max_data_object_id
and own 2 3 4 5 6 7 8 er = 'SCOTT';
Execution Plan
----------------------------------------------------------------
SQL hash value: 1214109186
Optimizer: ADOPT_C
+----+--------------------------------+----------------------+------------+----------+----------+-------------+----------+----------+----------+----------+--------------------------------+
| Id | Operation type | Name | Owner | E - Rows | A - Rows | Cost(%CPU) | A - Time | Loops | Memory | Disk | Partition info |
+----+--------------------------------+----------------------+------------+----------+----------+-------------+----------+----------+----------+----------+--------------------------------+
| 0 | SELECT STATEMENT | | | | 31| | 19245| 32| 0| 0| |
| 1 | SUBQUERY | QUERY[1] | | | 31| | 13584| 62| 0| 0| |
| 2 | AGGREGATE | | | 1| 31| 5( 0)| 13568| 62| 0| 0| |
|* 3 | TABLE ACCESS BY INDEX ROWID | TEST01 | SCOTT | 145| | 5( 0)| | | | | |
|* 4 | INDEX RANGE SCAN | IDX_TEST01_OBJECT_ID | SCOTT | 446| 15872| 1( 0)| 12120| 15903| 0| 0| |
|* 5 | VIEW | | | 12| 31| 225( 0)| 19242| 32| 0| 0| |
|* 6 | TABLE ACCESS FULL | TEST02 | SCOTT | 12| 31| 218( 0)| 5533| 32| 0| 0| |
+----+--------------------------------+----------------------+------------+----------+----------+-------------+----------+----------+----------+----------+--------------------------------+
Operation Information (identified by operation id):
---------------------------------------------------
3 - Predicate : filter("T3"."DATA_OBJECT_ID"[OPTMZ-1] IS NOT NULL)
4 - Predicate : access("T3"."OBJECT_ID" = "T2"."OBJECT_ID"[OPTMZ-3][OPTMZ-2])
5 - Predicate : filter("T2"."DATA_OBJECT_ID"[OPTMZ-3] = QUERY[1][OPTMZ-2])
6 - Predicate : filter("T2"."OWNER"[OPTMZ-1] = 'SCOTT'[OPTMZ-0] AND "T2"."DATA_OBJECT_ID"[OPTMZ-1] IS NOT NULL)
Statistics
----------------------------------------------------------------------------------------------------
0 physical reads
17283 db block gets
0 consistent gets
0 redo size
0 recursive calls
0 bytes sent via SQL*Net to client
0 bytes received via SQL*Net from client
0 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
31 rows processed
0 bytes sent via PX
0 block received
35 rows fetched.
Elapsed: 00:00:00.026结论：看上去原始SQL没有提前过滤t2.owner = 'SCOTT'，优化器有BUG