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1.基于规则的优化器

时间:2023-04-01 14:35:19浏览次数:41  
标签:基于 temp 00 EMPNO mgr emp 规则 优化 Plan

1.创建测试环境

--建表
create table emp_temp as select * from emp;
create index idx_mgr_temp on emp_temp(mgr);
create index idx_deptno_temp on emp_temp(deptno);
--查询数据库
select * 
from emp_temp
where mgr > 100 and deptno > 10;

     EMPNO ENAME      JOB	       MGR HIREDATE		      SAL	COMM	 DEPTNO
---------- ---------- --------- ---------- ------------------- ---------- ---------- ----------
      7369 SMITH      CLERK	      7902 1980-12-17 00:00:00	      800		     20
      7566 JONES      MANAGER	      7839 1981-04-02 00:00:00	     2975		     20
      7788 SCOTT      ANALYST	      7566 1987-04-19 00:00:00	     3000		     20
      7876 ADAMS      CLERK	      7788 1987-05-23 00:00:00	     1100		     20
      7902 FORD       ANALYST	      7566 1981-12-03 00:00:00	     3000		     20
      7499 ALLEN      SALESMAN	      7698 1981-02-20 00:00:00	     1600	 300	     30
      7521 WARD       SALESMAN	      7698 1981-02-22 00:00:00	     1250	 500	     30
      7654 MARTIN     SALESMAN	      7698 1981-09-28 00:00:00	     1250	1400	     30
      7698 BLAKE      MANAGER	      7839 1981-05-01 00:00:00	     2850		     30
      7844 TURNER     SALESMAN	      7698 1981-09-08 00:00:00	     1500	   0	     30
      7900 JAMES      CLERK	      7698 1981-12-03 00:00:00	      950		     30

11 rows selected.

2.测试RBO的执行计划

2.1.查看执行计划,执行SQL1:

select * from emp_temp  where mgr > 100 and deptno > 10;
scott@ORCLPDB01 2023-04-01 13:54:48> alter session set optimizer_mode = 'RULE';

Session altered.

Elapsed: 00:00:00.00
scott@ORCLPDB01 2023-04-01 13:54:53> set autot trace exp
scott@ORCLPDB01 2023-04-01 13:54:56> select * from emp_temp  where mgr > 100 and deptno > 10;
Elapsed: 00:00:00.00

Execution Plan
----------------------------------------------------------
Plan hash value: 1670750536

-------------------------------------------------------
| Id  | Operation		    | Name	      |
-------------------------------------------------------
|   0 | SELECT STATEMENT	    |		      |
|*  1 |  TABLE ACCESS BY INDEX ROWID| EMP_TEMP	      |
|*  2 |   INDEX RANGE SCAN	    | IDX_DEPTNO_TEMP |
-------------------------------------------------------

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

   1 - filter("MGR">100)
   2 - access("DEPTNO">10)

Note
-----
   - rule based optimizer used (consider using cbo)

2.2.通过等价改写SQL(加0或者空字符串的方式)修改执行计,划执行SQL2:

select * from emp_temp  where mgr > 100 and deptno + 0 > 10;
scott@ORCLPDB01 2023-04-01 13:55:12> select * from emp_temp  where mgr > 100 and deptno + 0 > 10;
Elapsed: 00:00:00.00

Execution Plan
----------------------------------------------------------
Plan hash value: 2973289657

----------------------------------------------------
| Id  | Operation		    | Name	   |
----------------------------------------------------
|   0 | SELECT STATEMENT	    |		   |
|*  1 |  TABLE ACCESS BY INDEX ROWID| EMP_TEMP	   |
|*  2 |   INDEX RANGE SCAN	    | IDX_MGR_TEMP |
----------------------------------------------------

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

   1 - filter("DEPTNO"+0>10)
   2 - access("MGR">100)

Note
-----
   - rule based optimizer used (consider using cbo)

 2.3.通过修改索引建立的顺序,调整执行计划(删除现有的索引,再新建索引,即是调整索引在数据字典中的顺序)

scott@ORCLPDB01 2023-04-01 13:59:44> drop index IDX_MGR_TEMP;

Index dropped.

Elapsed: 00:00:00.13
scott@ORCLPDB01 2023-04-01 14:05:45> create index idx_mgr_temp on emp_temp(mgr);

Index created.

Elapsed: 00:00:00.02
scott@ORCLPDB01 2023-04-01 14:06:02> select * from emp_temp  where mgr > 100 and deptno > 10;
Elapsed: 00:00:00.00

Execution Plan
----------------------------------------------------------
Plan hash value: 2973289657

----------------------------------------------------
| Id  | Operation		    | Name	   |
----------------------------------------------------
|   0 | SELECT STATEMENT	    |		   |
|*  1 |  TABLE ACCESS BY INDEX ROWID| EMP_TEMP	   |
|*  2 |   INDEX RANGE SCAN	    | IDX_MGR_TEMP |
----------------------------------------------------

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

   1 - filter("DEPTNO">10)
   2 - access("MGR">100)

Note
-----
   - rule based optimizer used (consider using cbo)

 2.4.验证改变目标SQL中涉及的对象在该SQL文本中出现的先后顺序,改变执行计划,划执行SQL3和SQL4:

--SQL3
scott@ORCLPDB01 2023-04-01 14:09:47> select t1.mgr,t2.deptno
  2  from emp_temp t1, emp_temp1 t2
  3  where t1.empno = t2.empno;
Elapsed: 00:00:00.00

Execution Plan
----------------------------------------------------------
Plan hash value: 1323777565

-----------------------------------------
| Id  | Operation	    | Name	|
-----------------------------------------
|   0 | SELECT STATEMENT    |		|
|   1 |  MERGE JOIN	    |		|
|   2 |   SORT JOIN	    |		|
|   3 |    TABLE ACCESS FULL| EMP_TEMP1 |
|*  4 |   SORT JOIN	    |		|
|   5 |    TABLE ACCESS FULL| EMP_TEMP	|
-----------------------------------------

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

   4 - access("T1"."EMPNO"="T2"."EMPNO")
       filter("T1"."EMPNO"="T2"."EMPNO")

Note
-----
   - rule based optimizer used (consider using cbo)

--SQL4
scott@ORCLPDB01 2023-04-01 14:10:27> select t1.mgr,t2.deptno
  2  from emp_temp1 t2, emp_temp t1
  3  where t1.empno = t2.empno;
Elapsed: 00:00:00.00

Execution Plan
----------------------------------------------------------
Plan hash value: 2135683657

-----------------------------------------
| Id  | Operation	    | Name	|
-----------------------------------------
|   0 | SELECT STATEMENT    |		|
|   1 |  MERGE JOIN	    |		|
|   2 |   SORT JOIN	    |		|
|   3 |    TABLE ACCESS FULL| EMP_TEMP	|
|*  4 |   SORT JOIN	    |		|
|   5 |    TABLE ACCESS FULL| EMP_TEMP1 |
-----------------------------------------

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

   4 - access("T1"."EMPNO"="T2"."EMPNO")
       filter("T1"."EMPNO"="T2"."EMPNO")

Note
-----
   - rule based optimizer used (consider using cbo)

2.5.通过修改执行路径等级制的大小选择执行计划(emp表empno列存在主键)执行SQL5和SQL6

scott@ORCLPDB01 2023-04-01 14:12:29> select t1.mgr,t2.deptno
  2  from emp t1, emp_temp t2
  3  where t1.empno = t2.empno;
Elapsed: 00:00:00.01

Execution Plan
----------------------------------------------------------
Plan hash value: 367190759

-------------------------------------------------
| Id  | Operation		     | Name	|
-------------------------------------------------
|   0 | SELECT STATEMENT	     |		|
|   1 |  NESTED LOOPS		     |		|
|   2 |   NESTED LOOPS		     |		|
|   3 |    TABLE ACCESS FULL	     | EMP_TEMP |
|*  4 |    INDEX UNIQUE SCAN	     | PK_EMP	|
|   5 |   TABLE ACCESS BY INDEX ROWID| EMP	|
-------------------------------------------------

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

   4 - access("T1"."EMPNO"="T2"."EMPNO")

Note
-----
   - rule based optimizer used (consider using cbo)

scott@ORCLPDB01 2023-04-01 14:18:34> select t1.mgr,t2.deptno
  2  from  emp_temp t2,emp t1
  3  where t1.empno = t2.empno;
Elapsed: 00:00:00.00

Execution Plan
----------------------------------------------------------
Plan hash value: 367190759

-------------------------------------------------
| Id  | Operation		     | Name	|
-------------------------------------------------
|   0 | SELECT STATEMENT	     |		|
|   1 |  NESTED LOOPS		     |		|
|   2 |   NESTED LOOPS		     |		|
|   3 |    TABLE ACCESS FULL	     | EMP_TEMP |
|*  4 |    INDEX UNIQUE SCAN	     | PK_EMP	|
|   5 |   TABLE ACCESS BY INDEX ROWID| EMP	|
-------------------------------------------------

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

   4 - access("T1"."EMPNO"="T2"."EMPNO")

Note
-----
   - rule based optimizer used (consider using cbo)

注意:如果RBO仅凭目标SQL各执行路径等级值的大小就可以选择执行计划,无论怎么调整位置,对于该SQL的最终执行计划没有任何影响。 

标签:基于,temp,00,EMPNO,mgr,emp,规则,优化,Plan
From: https://www.cnblogs.com/yuanzijian/p/17278578.html

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