oracle 提供了优化建议功能包DBMS_SQLTUNE，该包可以帮助我们分析SQL，并提供优化建议。
Sql_Profile是用来影响数据库执行计划生成的一组信息文件的集合，可以在不改变原有SQL语句的前提下，达到类似HINTS改变其执行计划的目的。
原有执行计划
alter session set statistics_level=all;
set serveroutput off
select * from test.emp where ename='SCOTT' and DEPTNO=20;
SELECT * FROM table(dbms_xplan.display_cursor(NULL,NULL,'runstats_last'));
PLAN_TABLE_OUTPUT
------------------------------------------------------------------------------------------------------------------------
SQL_ID 8k1gbrapm7zpd, child number 0
-------------------------------------
select * from test.emp where ename='SCOTT' and DEPTNO=20
Plan hash value: 3956160932
------------------------------------------------------------------------------------
| Id | Operation | Name | Starts | E-Rows | A-Rows | A-Time | Buffers |
------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | | 1 |00:00:00.01 | 4 |
|* 1 | TABLE ACCESS FULL| EMP | 1 | 1 | 1 |00:00:00.01 | 4 |
-------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - filter(("ENAME"='SCOTT' AND "DEPTNO"=20))
下面就用DBMS_SQLTUNE优化该SQL
--1.赋予用户ADVISOR权限
grant ADVISOR to test;
--2.创建sql tuning任务
conn test/test
DECLARE my_task_name VARCHAR2(30); my_sqltext CLOB; BEGIN my_sqltext := 'select * from emp where ename= :name and DEPTNO= :deptno'; my_task_name := DBMS_SQLTUNE.CREATE_TUNING_TASK( sql_text => my_sqltext, bind_list => sql_binds(anydata.convertvarchar2(10),anydata.convertnumber(2)), user_name => 'TEST', scope => 'COMPREHENSIVE', time_limit => 60, task_name => 'test_sql_tuning', description => 'Task to tune a query on emp'); END; /
注意:
记住，DBMS_SQLTUNE.CREATE_TUNING_TASK是一个函数，必须要有返回值。
上面在定义了一个TASK后，可通过DBMS_SQLTUNE.EXECUTE_TUNING_TASK来执行此调优过程。
bind_list：
多个绑定变量以','逗号分隔。参数值一定要根据绑定变量对应的列的类型书写.
如：emp.ename类型是VARCHAR2(10)，那么就要写成
bind_list =>sql_binds(anydata.convertvarchar2(10)),
time_limit：
执行的最长时间，默认是60。
scope：
LIMITED，用大概1秒时间去优化SQL语句，但是并不进行SQL Profiling分析。
COMPREHENSIVE，进行全面分析，包含SQL Profiling分析；比LIMITED用时更长。
**也可以用sql_id创建sql tunning任务，比用sql_text方便很多
FUNCTION CREATE_TUNING_TASK RETURNS VARCHAR2 Argument Name Type In/Out Default? ------------------------------ ----------------------- ------ -------- SQL_ID VARCHAR2 IN PLAN_HASH_VALUE NUMBER IN DEFAULT SCOPE VARCHAR2 IN DEFAULT TIME_LIMIT NUMBER IN DEFAULT TASK_NAME VARCHAR2 IN DEFAULT DESCRIPTION VARCHAR2 IN DEFAULT DECLARE my_task_name VARCHAR2(30); BEGIN my_task_name := DBMS_SQLTUNE.CREATE_TUNING_TASK( SQL_ID => 'ddw7j6yfnw0vz', scope => 'COMPREHENSIVE', ----------->任务类型，有limited和comprehensive两种 time_limit => 60, ----------->此任务最长的执行时间 task_name => 'tunning_task_ddw7j6yfnw0vz', ----------->任务名 description => 'Task to tune a query on ddw7j6yfnw0vz' ----------->任务描述 ); END; /
--3.查看任务名 SELECT TASK_NAME
FROM DBA_ADVISOR_LOG
WHERE OWNER = 'TEST';
TASK_NAME
------------------------------
test_sql_tuning
--4.执行sql tuning任务
BEGIN DBMS_SQLTUNE.EXECUTE_TUNING_TASK( task_name => 'test_sql_tuning', ------------>任务名 execution_name => NULL, ----------->执行时的名称，可为空 execution_params => NULL, ------------>执行参数，默认可为空 execution_desc => NULL ------------>执行描述 );END;/
--5.查看sql tunning任务状态
SELECT status FROM USER_ADVISOR_TASKS WHERE task_name = 'test_sql_tuning'; STATUS ----------- COMPLETED
--6.展示sql tunning结果
SET LONG 10000
SET LONGCHUNKSIZE 1000
SET LINESIZE 100
SELECT DBMS_SQLTUNE.REPORT_TUNING_TASK('test_sql_tuning')
FROM DUAL;
DBMS_SQLTUNE.REPORT_TUNING_TASK('TEST_SQL_TUNING')
----------------------------------------------------------------------------------------------------
GENERAL INFORMATION SECTION
-------------------------------------------------------------------------------
Tuning Task Name : test_sql_tuning
Tuning Task Owner : TEST
Workload Type : Single SQL Statement
Scope : COMPREHENSIVE
Time Limit(seconds): 60
Completion Status : COMPLETED
Started at : 04/01/2014 16:45:16
Completed at : 04/01/2014 16:45:17
DBMS_SQLTUNE.REPORT_TUNING_TASK('TEST_SQL_TUNING')
----------------------------------------------------------------------------------------------------
-------------------------------------------------------------------------------
Schema Name: TEST
SQL ID : 95fv6dbj64d0f
SQL Text : select * from emp where ename= :name and DEPTNO= :deptno
-------------------------------------------------------------------------------
FINDINGS SECTION (2 findings)
-------------------------------------------------------------------------------
1- Statistics Finding
---------------------
DBMS_SQLTUNE.REPORT_TUNING_TASK('TEST_SQL_TUNING')
----------------------------------------------------------------------------------------------------
Table "TEST"."EMP" was not analyzed.
Recommendation
--------------
- Consider collecting optimizer statistics for this table.
execute dbms_stats.gather_table_stats(ownname => 'TEST', tabname =>
'EMP', estimate_percent => DBMS_STATS.AUTO_SAMPLE_SIZE,
method_opt => 'FOR ALL COLUMNS SIZE AUTO');
Rationale
---------
DBMS_SQLTUNE.REPORT_TUNING_TASK('TEST_SQL_TUNING')
----------------------------------------------------------------------------------------------------
The optimizer requires up-to-date statistics for the table in order to
select a good execution plan.
2- Index Finding (see explain plans section below)
--------------------------------------------------
The execution plan of this statement can be improved by creating one or more
indices.
Recommendation (estimated benefit: 66.67%)
------------------------------------------
- Consider running the Access Advisor to improve the physical schema design
DBMS_SQLTUNE.REPORT_TUNING_TASK('TEST_SQL_TUNING')
----------------------------------------------------------------------------------------------------
or creating the recommended index.
create index TEST.IDX$$_00D80001 on TEST.EMP("ENAME","DEPTNO");
Rationale
---------
Creating the recommended indices significantly improves the execution plan
of this statement. However, it might be preferable to run "Access Advisor"
using a representative SQL workload as opposed to a single statement. This
will allow to get comprehensive index recommendations which takes into
account index maintenance overhead and additional space consumption.
DBMS_SQLTUNE.REPORT_TUNING_TASK('TEST_SQL_TUNING')
----------------------------------------------------------------------------------------------------
-------------------------------------------------------------------------------
EXPLAIN PLANS SECTION
-------------------------------------------------------------------------------
1- Original
-----------
Plan hash value: 3956160932
--------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
--------------------------------------------------------------------------
DBMS_SQLTUNE.REPORT_TUNING_TASK('TEST_SQL_TUNING')
----------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 87 | 3 (0)| 00:00:01 |
|* 1 | TABLE ACCESS FULL| EMP | 1 | 87 | 3 (0)| 00:00:01 |
--------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - filter("ENAME"=:NAME AND "DEPTNO"=:DEPTNO)
2- Using New Indices
--------------------
DBMS_SQLTUNE.REPORT_TUNING_TASK('TEST_SQL_TUNING')
----------------------------------------------------------------------------------------------------
Plan hash value: 2106247215
----------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
----------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 87 | 1 (0)| 00:00:01 |
| 1 | TABLE ACCESS BY INDEX ROWID| EMP | 1 | 87 | 1 (0)| 00:00:01 |
|* 2 | INDEX RANGE SCAN | IDX$$_00D80001 | 1 | | 1 (0)| 00:00:01 |
----------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
DBMS_SQLTUNE.REPORT_TUNING_TASK('TEST_SQL_TUNING')
----------------------------------------------------------------------------------------------------
---------------------------------------------------
2 - access("ENAME"=:NAME AND "DEPTNO"=:DEPTNO)
-------------------------------------------------------------------------------
建议报告总结：
<1>收集EMP表的统计信息
execute dbms_stats.gather_table_stats(ownname => 'TEST', tabname =>'EMP', estimate_percent => DBMS_STATS.AUTO_SAMPLE_SIZE,method_opt => 'FOR ALL COLUMNS SIZE AUTO');
<2>创建索引
create index TEST.IDX$$_00D80001 on TEST.EMP("ENAME","DEPTNO");
优化后执行计划
--------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Starts | E-Rows | A-Rows | A-Time | Buffers |
--------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | | 1 |00:00:00.01 | 3 |
| 1 | TABLE ACCESS BY INDEX ROWID| EMP | 1 | 1 | 1 |00:00:00.01 | 3 |
|* 2 | INDEX RANGE SCAN | IDX$$_00D80001 | 1 | 1 | 1 |00:00:00.01 | 2 |
--------------------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
2 - access("ENAME"='SCOTT' AND "DEPTNO"=20)
ACCEPT_SQL_PROFILE #接受及应用一个SQL_PROFILE执行计划给某条SQL
DBMS_SQLTUNE.ACCEPT_SQL_PROFILE ( task_name IN VARCHAR2, -------------->执行优化的任务名 object_id IN NUMBER := NULL, -------------->对象编号，一般不填 name IN VARCHAR2 := NULL, -------------->制定的sql_profile名称，如果不填则由系统指派 description IN VARCHAR2 := NULL, -------------->该执行计划的描述信息 category IN VARCHAR2 := NULL); ------------->需要与该SESSION的sqltune_category参数相匹配 task_owner IN VARCHAR2 := NULL, ------------->任务的所有者 replace IN BOOLEAN := FALSE, ------------->如果此sql_profile已存在，则决定是否替换，默认值为不替换 force_match IN BOOLEAN := FALSE, ------------->是否强制匹配此执行计划与所有HASH值相同的SQL，类似CURSOR_SHARING参数的FORCE profile_type IN VARCHAR2 := REGULAR_PROFILE); ------------->sql_profile的类型，默认为REGULAR_PROFILE，可修改为PX_PROFILE，表示此执行计划变更为并行执行 DROP_SQL_PROFILE DBMS_SQLTUNE.DROP_SQL_PROFILE ( #删除一个SQL_PROFILE的应用，让系统自动选择 name IN VARCHAR2, ignore IN BOOLEAN := FALSE);
--7.完成后删除sql tunning任务
EXEC DBMS_SQLTUNE.DROP_TUNING_TASK('test_sql_tuning');
--8.其他
--sql tunning任务创建后，也可以修改参数 BEGIN DBMS_SQLTUNE.SET_TUNING_TASK_PARAMETER( task_name => 'test_sql_tuning', parameter => 'TIME_LIMIT', value => 300); END; / --查看SQL Tuning Advisor的进展（task执行很久） col opname for a20 col ADVISOR_NAME for a20 SELECT SID,SERIAL#,USERNAME,OPNAME,ADVISOR_NAME,TARGET_DESC,START_TIME SOFAR, TOTALWORK FROM V$ADVISOR_PROGRESS WHERE USERNAME = 'TEST';