집합 연산을 조인으로 변환

1. intersect나 minus 같은 집합 연산을 조인 형태로 변환
2. sys_op_map_nonnull 함수 : 비공식적인 함수. null끼리 "=" 비교(null = null)하면 false이지만, 가끔 true가 되도록 처리할 때 사용

테스트

• join형태로 변환1

select job, mgr from emp
minus
select job, mgr from emp
where  deptno = 10 ;

Execution Plan
----------------------------------------------------------
Plan hash value: 4030040631

----------------------------------------------------------------------------
| Id  | Operation           | Name | Rows  | Bytes | Cost (%CPU)| Time     |
----------------------------------------------------------------------------
|   0 | SELECT STATEMENT    |      |    13 |  1157 |     8  (25)| 00:00:01 |
|   1 |  HASH UNIQUE        |      |    13 |  1157 |     8  (25)| 00:00:01 |
|*  2 |   HASH JOIN ANTI    |      |    13 |  1157 |     7  (15)| 00:00:01 |
|   3 |    TABLE ACCESS FULL| EMP  |    14 |   532 |     3   (0)| 00:00:01 |
|*  4 |    TABLE ACCESS FULL| EMP  |     3 |   153 |     3   (0)| 00:00:01 |
----------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

   2 - access(SYS_OP_MAP_NONNULL("JOB")=SYS_OP_MAP_NONNULL("JOB") AND
              SYS_OP_MAP_NONNULL("MGR")=SYS_OP_MAP_NONNULL("MGR"))
   4 - filter("DEPTNO"=10)

• _convert_set_to_join" = true
  • hash anti join 수행 후, 중복값 제거를 위해 hash unique 연산 수행으로 쿼리 변환

select job, mgr from emp
minus
select job, mgr from emp
where  deptno = 10 ;

Execution Plan
----------------------------------------------------------
Plan hash value: 4030040631

----------------------------------------------------------------------------
| Id  | Operation           | Name | Rows  | Bytes | Cost (%CPU)| Time     |
----------------------------------------------------------------------------
|   0 | SELECT STATEMENT    |      |    13 |  1157 |     8  (25)| 00:00:01 |
|   1 |  HASH UNIQUE        |      |    13 |  1157 |     8  (25)| 00:00:01 |
|*  2 |   HASH JOIN ANTI    |      |    13 |  1157 |     7  (15)| 00:00:01 |
|   3 |    TABLE ACCESS FULL| EMP  |    14 |   532 |     3   (0)| 00:00:01 |
|*  4 |    TABLE ACCESS FULL| EMP  |     3 |   153 |     3   (0)| 00:00:01 |
----------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------
   2 - access(SYS_OP_MAP_NONNULL("JOB")=SYS_OP_MAP_NONNULL("JOB") AND
              SYS_OP_MAP_NONNULL("MGR")=SYS_OP_MAP_NONNULL("MGR"))
   4 - filter("DEPTNO"=10)

**************************
Predicate Move-Around (PM)
**************************
PM: Considering predicate move-around in SEL$09AAA538 (#0).
PM:   Checking validity of predicate move-around in SEL$09AAA538 (#0).
PM:     PM bypassed: Outer query contains no views.
FPD: Considering simple filter push in SEL$09AAA538 (#0)
FPD:   Current where clause predicates in SEL$09AAA538 (#0) :
         "EMP"."DEPTNO"=10 AND SYS_OP_MAP_NONNULL("EMP"."JOB")=SYS_OP_MAP_NONNULL("EMP"."JOB") AND SYS_OP_MAP_NONNULL("EMP"."MGR")=SYS_OP_MAP_NONNULL("EMP"."MGR")
kkogcp: try to generate transitive predicate from check constraints for SEL$09AAA538 (#0)
predicates with check contraints: "EMP"."DEPTNO"=10 AND SYS_OP_MAP_NONNULL("EMP"."JOB")=SYS_OP_MAP_NONNULL("EMP"."JOB") AND SYS_OP_MAP_NONNULL("EMP"."MGR")=SYS_OP_MAP_NONNULL("EMP"."MGR")
after transitive predicate generation: "EMP"."DEPTNO"=10 AND SYS_OP_MAP_NONNULL("EMP"."JOB")=SYS_OP_MAP_NONNULL("EMP"."JOB") AND SYS_OP_MAP_NONNULL("EMP"."MGR")=SYS_OP_MAP_NONNULL("EMP"."MGR")
finally: "EMP"."DEPTNO"=10 AND SYS_OP_MAP_NONNULL("EMP"."JOB")=SYS_OP_MAP_NONNULL("EMP"."JOB") AND SYS_OP_MAP_NONNULL("EMP"."MGR")=SYS_OP_MAP_NONNULL("EMP"."MGR")

• not exists의 경우

Current SQL statement for this session:
select distinct job, mgr from emp e
where  not exists (
  select 'x' from emp
  where  deptno = 10
  and    sys_op_map_nonnull(job) = sys_op_map_nonnull(e.job)
  and    sys_op_map_nonnull(mgr) = sys_op_map_nonnull(e.mgr)
) ;

Execution Plan
----------------------------------------------------------
Plan hash value: 4030040631

----------------------------------------------------------------------------
| Id  | Operation           | Name | Rows  | Bytes | Cost (%CPU)| Time     |
----------------------------------------------------------------------------
|   0 | SELECT STATEMENT    |      |    13 |   663 |     8  (25)| 00:00:01 |
|   1 |  HASH UNIQUE        |      |    13 |   663 |     8  (25)| 00:00:01 |
|*  2 |   HASH JOIN ANTI    |      |    13 |   663 |     7  (15)| 00:00:01 |
|   3 |    TABLE ACCESS FULL| EMP  |    14 |   266 |     3   (0)| 00:00:01 |
|*  4 |    TABLE ACCESS FULL| EMP  |     3 |    96 |     3   (0)| 00:00:01 |
----------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------
   2 - access(SYS_OP_MAP_NONNULL("JOB")=SYS_OP_MAP_NONNULL("E"."JOB")
              AND SYS_OP_MAP_NONNULL("MGR")=SYS_OP_MAP_NONNULL("E"."MGR"))
   4 - filter("DEPTNO"=10)

**************************
Predicate Move-Around (PM)
**************************
PM: Considering predicate move-around in SEL$5DA710D3 (#1).
PM:   Checking validity of predicate move-around in SEL$5DA710D3 (#1).
PM:     PM bypassed: Outer query contains no views.
JPPD: Applying transformation directives
JPPD: Checking validity of push-down in query block SEL$5DA710D3 (#1)
JPPD:   No view found to push predicate into.
FPD: Considering simple filter push in SEL$5DA710D3 (#1)
FPD:   Current where clause predicates in SEL$5DA710D3 (#1) :
         "EMP"."DEPTNO"=10 AND SYS_OP_MAP_NONNULL("EMP"."JOB")=SYS_OP_MAP_NONNULL("E"."JOB") AND SYS_OP_MAP_NONNULL("EMP"."MGR")=SYS_OP_MAP_NONNULL("E"."MGR")
kkogcp: try to generate transitive predicate from check constraints for SEL$5DA710D3 (#1)
predicates with check contraints: "EMP"."DEPTNO"=10 AND SYS_OP_MAP_NONNULL("EMP"."JOB")=SYS_OP_MAP_NONNULL("E"."JOB") AND SYS_OP_MAP_NONNULL("EMP"."MGR")=SYS_OP_MAP_NONNULL("E"."MGR")
after transitive predicate generation: "EMP"."DEPTNO"=10 AND SYS_OP_MAP_NONNULL("EMP"."JOB")=SYS_OP_MAP_NONNULL("E"."JOB") AND SYS_OP_MAP_NONNULL("EMP"."MGR")=SYS_OP_MAP_NONNULL("E"."MGR")
finally: "EMP"."DEPTNO"=10 AND SYS_OP_MAP_NONNULL("EMP"."JOB")=SYS_OP_MAP_NONNULL("E"."JOB") AND SYS_OP_MAP_NONNULL("EMP"."MGR")=SYS_OP_MAP_NONNULL("E"."MGR")