Oracle 10G强大的SQL优化工具：SQL Tuning Advisor
2016年11月14日
15:05
Oracle 10G推出了强大的SQL优化工具：SQL Tuning Advisor，使用该功能必须保证优化器是CBO模式，对SQL进行优化需要执行DBMS_SQLTUNE包，因而需要advisor权限。
举个例子介绍如何优化一条发现问题的语句
--1.创建测试环境
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SQL> show user;
USER is "SYS"
--授予普通用户advisor的权限 SQL> grant advisor to owner;
Grant succeeded.
SQL> conn owner/owner
Connected.
SQL> create table test1114 as select * from dba_objects;
SQL> insert into test1114 select * from dba_objects;
SQL> set timing on SQL> set autot on
SQL> select * from test1114;
Elapsed: 00:01:09.81
Execution Plan ---------------------------------------------------------- Plan hash value: 3447467757
------------------------------------------------------------------------------ | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | ------------------------------------------------------------------------------ | 0 | SELECT STATEMENT | | 110K| 21M| 588 (1)| 00:00:08 | | 1 | TABLE ACCESS FULL| TEST1114 | 110K| 21M| 588 (1)| 00:00:08 | ------------------------------------------------------------------------------
Note ----- - dynamic sampling used for this statement (level=2)
Statistics ---------------------------------------------------------- 29 recursive calls 1 db block gets 11646 consistent gets 1080 physical reads 176 redo size 16498937 bytes sent via SQL*Net to client 106046 bytes received via SQL*Net from client 9595 SQL*Net roundtrips to/from client 0 sorts (memory) 0 sorts (disk) 143898 rows processed |
--2.创建优化任务
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步骤一: 调用函数CREATE_TUNING_TASK来创建优化任务； 步骤二: 调用存储过程EXECUTE_TUNING_TASK执行该任务；
SQL>set autotrace off SQL>set timing off
SQL> declare owner_sql varchar2(30); sqltext_me clob;
begin
sqltext_me := 'select * from test1114';
--删除优化任务 dbms_sqltune.drop_tuning_task(task_name =>'tuning_owner_test');
--创建优化任务 owner_sql := dbms_sqltune.create_tuning_task ( sql_text => sqltext_me, user_name => 'OWNER', scope => 'comprehensive', time_limit => 60, task_name => 'tuning_owner_test', description => 'task to tune a query on a specified table') ;
--执行优化任务 dbms_sqltune.execute_tuning_task( task_name => 'tuning_owner_test'); end; /
PL/SQL procedure successfully completed. |
--3.执行优化任务
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调用dbms_sqltune.execute_tuning_task过程来执行前面创建好的优化任务。
SQL> exec dbms_sqltune.execute_tuning_task('tuning_owner_test');
PL/SQL procedure successfully completed. |
--4.检查优化任务的状态
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-通过查看dba_advisor_task或者suser_advisor_tasks可以检查优化任务的状态
SQL> SELECT task_name,status FROM USER_ADVISOR_TASKS WHERE task_name ='tuning_owner_test';
TASK_NAME STATUS ------------------------------ ----------- tuning_owner_test COMPLETED |
--5.查看优化结果
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查询dbms_sqltune.report_tning_task函数可以获得优化任务的结果
SQL> set long 888888 SQL> set serveroutput on size 888888 SQL> set lines 100
SQL> select dbms_sqltune.report_tuning_task('tuning_owner_test') from dual;
DBMS_SQLTUNE.REPORT_TUNING_TASK('TUNING_OWNER_TEST1500') -------------------------------------------------------------------------------- GENERAL INFORMATION SECTION ------------------------------------------------------------------------------- Tuning Task Name : tuning_owner_test1500 Tuning Task Owner : OWNER Workload Type : Single SQL Statement Execution Count : 2 Current Execution : EXEC_146 Execution Type : TUNE SQL Scope : COMPREHENSIVE Time Limit(seconds): 60 Completion Status : COMPLETED Started at : 11/14/2016 15:00:36 Completed at : 11/14/2016 15:00:37
------------------------------------------------------------------------------- Schema Name: OWNER SQL ID : dzrzmbsu9krk8 SQL Text : select * from test1114
------------------------------------------------------------------------------- FINDINGS SECTION (1 finding) -------------------------------------------------------------------------------
1- Statistics Finding --------------------- Table "OWNER"."TEST1114" was not analyzed.
Recommendation -------------- - Consider collecting optimizer statistics for this table. execute dbms_stats.gather_table_stats(ownname => 'OWNER', tabname => 'TEST1114', estimate_percent => DBMS_STATS.AUTO_SAMPLE_SIZE, method_opt => 'FOR ALL COLUMNS SIZE AUTO');
Rationale --------- The optimizer requires up-to-date statistics for the table in order to select a good execution plan.
------------------------------------------------------------------------------- EXPLAIN PLANS SECTION -------------------------------------------------------------------------------
1- Original ----------- Plan hash value: 3447467757
------------------------------------------------------------------------------ | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | ------------------------------------------------------------------------------ | 0 | SELECT STATEMENT | | 139K| 27M| 588 (1)| 00:00:08 | | 1 | TABLE ACCESS FULL| TEST1114 | 139K| 27M| 588 (1)| 00:00:08 | ------------------------------------------------------------------------------
------------------------------------------------------------------------------- 分析语句为
execute dbms_stats.gather_table_stats(ownname => 'OWNER', tabname => 'TEST1114', estimate_percent => DBMS_STATS.AUTO_SAMPLE_SIZE, method_opt => 'FOR ALL COLUMNS SIZE AUTO'); |
--6.删除优化任务
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调用dbms_sqltuen.drop_tuning_task删除已经存在的优化任务
SQL> exec dbms_sqltune.drop_tuning_task('tuning_kingsql_test1500');
PL/SQL procedure successfully completed. |