当前位置：Gxlcms > 数据库问题 > 使用hint优化Oracle的运行计划以及 SQL Tune Advisor的使用

使用hint优化Oracle的运行计划以及 SQL Tune Advisor的使用

时间：2021-07-01 10:21:17 帮助过：4人阅读

OS:Red Hat Linux As 5 DB:10.2.0.4 ? Oracle通过STA给出某个SQL运行建议,以下通过一个測试检查Oracle给出的优化建议是否正确. ? 1.建表并生成測试数据 SQL> create table tb_test(id number not null,name varchar2(30)); Table created. SQL> create index idx_tb_test on tb_test(id); Index created. SQL> declare
begin
? for i in 1 .. 100000 loop
??? insert into tb_test values (i, ‘test‘);
??? commit;
? end loop;
end;
/ ? 2.分析表 begin
? dbms_stats.gather_table_stats(ownname => ‘SCOTT‘, tabname => ‘TB_TEST‘);
end;

3.编造一个运行计划不正确的SQL

select/*+ full(t)*/ count(1) from scott.tb_test t where t.id=1

我们知道在ID列上有索引,这个SQL走索引是正确的运行计划,但这里强制oracle走全表扫描,然后通过STA,看oracle给出的运行计划是否正确.

4.创建TUNING_TASK并运行

declare
? l_task_name varchar2(30);
? l_sql?????? clob;
begin
? l_sql?????? := ‘select/*+ full(t)*/ count(1) from scott.tb_test t where t.id=1‘;
? l_task_name := DBMS_SQLTUNE.CREATE_TUNING_TASK(sql_text??? => l_sql,
???????????????????????????????????????????????? user_name?? => ‘SCOTT‘,
???????????????????????????????????????????????? scope?????? => ‘COMPREHENSIVE‘,
???????????????????????????????????????????????? time_limit? => 60,
???????????????????????????????????????????????? task_name?? => ‘task_name01‘,
???????????????????????????????????????????????? description => null);
dbms_sqltune.Execute_tuning_task(task_name => ‘task_name01‘);
end;

5.查看oracle给出的优化建议

SQL> set serveroutput on;
SQL> set long 999999999;
SQL> SELECT DBMS_SQLTUNE.REPORT_TUNING_TASK(‘task_name01‘) FROM DUAL;

DBMS_SQLTUNE.REPORT_TUNING_TASK(‘TASK_NAME01‘)
--------------------------------------------------------------------------------
GENERAL INFORMATION SECTION
-------------------------------------------------------------------------------
Tuning Task Name????????????????? : task_name01
Tuning Task Owner???????????????? : SYS
Scope???????????????????????????? : COMPREHENSIVE
Time Limit(seconds)?????????????? : 60
Completion Status???????????????? : COMPLETED
Started at??????????????????????? : 06/03/2012 00:07:58
Completed at????????????????????? : 06/03/2012 00:07:59
Number of SQL Profile Findings??? : 1

DBMS_SQLTUNE.REPORT_TUNING_TASK(‘MY_TASK_NAME01‘)
--------------------------------------------------------------------------------
-------------------------------------------------------------------------------
Schema Name: SCOTT
SQL ID???? : ga3q5tqjgsj5u
SQL Text?? : select/*+ full(t)*/ count(1) from scott.tb_test t where t.id=1

-------------------------------------------------------------------------------
FINDINGS SECTION (1 finding)
-------------------------------------------------------------------------------

1- SQL Profile Finding (see explain plans section below)
--------------------------------------------------------

DBMS_SQLTUNE.REPORT_TUNING_TASK(‘MY_TASK_NAME01‘)
--------------------------------------------------------------------------------
? A potentially better execution plan was found for this statement.

? Recommendation (estimated benefit: 84.11%)
? ------------------------------------------
? - Consider accepting the recommended SQL profile.
??? execute dbms_sqltune.accept_sql_profile(task_name => ‘task_name01‘,
??????????? replace => TRUE);

-------------------------------------------------------------------------------
EXPLAIN PLANS SECTION
-------------------------------------------------------------------------------

DBMS_SQLTUNE.REPORT_TUNING_TASK(‘TASK_NAME01‘)
--------------------------------------------------------------------------------

1- Original With Adjusted Cost
------------------------------
Plan hash value: 1372292586

--------------------------------------------------------------------------------

--------------------------------------------------------------------------------

-- 当前的运行计划
DBMS_SQLTUNE.REPORT_TUNING_TASK(‘TASK_NAME01‘)
--------------------------------------------------------------------------------
|?? 0 | SELECT STATEMENT?? |?????????? |???? 1 |???? 4 |???? 6?? (0)| 00:00:01 |

|?? 1 |? SORT AGGREGATE??? |?????????? |???? 1 |???? 4 |??????????? |????????? |

|*? 2 |?? TABLE ACCESS FULL| TB_TEST? ?|???? 1 |???? 4 |???? 6?? (0)| 00:00:01 |

--------------------------------------------------------------------------------

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

DBMS_SQLTUNE.REPORT_TUNING_TASK(‘TASK_NAME01‘)
--------------------------------------------------------------------------------

?? 2 - filter("T"."ID"=1)

-- Oracle给出的运行计划

2- Using SQL Profile
--------------------
Plan hash value: 847665939

DBMS_SQLTUNE.REPORT_TUNING_TASK(‘TASK_NAME01‘)
--------------------------------------------------------------------------------
--------------------------------------------------------------------------------
---
|?? 0 | SELECT STATEMENT? |?????????????? |???? 1 |???? 4 |???? 1?? (0)| 00:00:0
1 |
|?? 1 |? SORT AGGREGATE?? |?????????????? |???? 1 |???? 4 |??????????? |
? |
|*? 2 |?? INDEX RANGE SCAN| IDX_TB_TEST? ?|???? 1 |???? 4 |???? 1?? (0)| 00:00:0
1 |
--------------------------------------------------------------------------------
---

DBMS_SQLTUNE.REPORT_TUNING_TASK(‘TASK_NAME01‘)
--------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------

?? 2 - access("T"."ID"=1)

-------------------------------------------------------------------------------

从上面的输出能够看出Oracle给出的运行计划是正确的.能够使用例如以下方法使用正确的运行计划

begin
? dbms_sqltune.accept_sql_profile(task_name => ‘task_name01‘, replace => TRUE);
end;

-- The End --

使用hint优化Oracle的运行计划以及 SQL Tune Advisor的使用

标签：statement 详细分析 code jad hat 数据集 ESS int red

使用hint优化Oracle的运行计划 以及 SQL Tune Advisor的使用

人气教程排行

使用hint优化Oracle的运行计划以及 SQL Tune Advisor的使用