数据库版本崖山23.5.1SQL 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SQLselect * 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