如何用 SQL Tuning&nbsp…
2014-11-25 18:07
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如何用 SQL Tuning Advisor (STA) 优化SQL语句
在Oracle10g之前,优化SQL是个比较费力的技术活,不停的分析执行计划,加hint,分析统计信息等等。在10g中,Oracle推出了自己的SQL优化辅助工具:
SQL优化器(SQL Tuning Advisor
:STA),它是新的DBMS_SQLTUNE包。使用STA一定要保证优化器是CBO模式下。
执行DBMS_SQLTUNE包进行sql优化需要有advisor的权限:
SQL> create user dave identified by dave;
用户已创建。
SQL> grant connect,resource to dave;
授权成功。
SQL> grant advisor to dave;
授权成功。
下面简单介绍一下如何优化一条找到的问题语句。
create table bigtab as select rownum as "id",a.* from
sys.all_objects a;
create table smalltab as select rownum as "id", a.* FROM
sys.all_tables a;
然后多运行几次下面的脚本,增加表里的数据:
insert into bigtab select rownum as "id",a.* from sys.all_objects
a;
insert into smalltab select rownum as "id", a.* FROM sys.all_tables
a;
这里创建一张大表和一张小表,并且都没有索引,下面执行一个查询:
SQL> set timing on
SQL> set autot on
SQL> select count(*) from bigtab a, smalltab b where
a.object_name=b.table_name;
COUNT(*)
----------
2141537
已用时间: 00: 00: 20.05
执行计划
----------------------------------------------------------
Plan hash value: 3089226980
--------------------------------------------------------------------------------
| Id |
Operation
|
Name
| Rows | Bytes | Cost (%CPU)|
Time
|
--------------------------------------------------------------------------------
| 0 | SELECT
STATEMENT
|
|
1 | 45
| 3146 (1)|
00:00:38 |
| 1 | SORT
AGGREGATE
|
|
1 | 45
|
|
|
|* 2 | HASH
JOIN
|
|
447K|
19M| 3146
(1)| 00:00:38 |
| 3
| TABLE
ACCESS FULL| SMALLTAB | 27327 |
533K|
264 (1)| 00:00:04 |
| 4
| TABLE
ACCESS FULL| BIGTAB
|
712K|
16M| 2878
(1)| 00:00:35 |
--------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
2 -
access("A"."OBJECT_NAME"="B"."TABLE_NAME")
统计信息
----------------------------------------------------------
0 recursive calls
0 db block gets
31149 consistent gets
21058 physical reads
0 redo size
426 bytes sent via SQL*Net to client
416 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
1 rows processed
第一步:创建优化任务
通过调用函数CREATE_TUNING_TASK来创建优化任务,调用存储过程EXECUTE_TUNING_TASK执行该任务:
SQL> set autot off
SQL> set timing off
SQL> DECLARE
2
my_task_name VARCHAR2(30);
3
my_sqltext CLOB;
4 BEGIN
5 my_sqltext
:= 'select count(*) from bigtab a, smalltab b where
a.object_name=b.table_name';
6
my_task_name := DBMS_SQLTUNE.CREATE_TUNING_TASK(
7
sql_text
=> my_sqltext,
8
user_name =>
'DAVE', --
注意是大写,不然会报错,用户无效
9
scope
=> 'COMPREHENSIVE',
10
time_limit => 60,
11
task_name =>
'tuning_sql_test',
12
description => 'Task to tune a query on a specified
table');
13
14
DBMS_SQLTUNE.EXECUTE_TUNING_TASK( task_name =>
'tuning_sql_test');
15 END;
16 /
PL/SQL procedure successfully completed.
在函数CREATE_TUNING_TASK,sql_text是需要优化的语句,user_name是该语句通过哪个用户执行,scope是优化范围(limited或comprehensive),time_limit优化过程的时间限制,task_name优化任务名称,description优化任务描述。
第二步: 执行优化任务
通过调用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_sql_test');
PL/SQL 过程已成功完成。
第三步:检查优化任务的状态
通过查看user_advisor_tasks/dba_advisor_tasks视图可以查看优化任务的当前状态。
SQL> SELECT task_name,status FROM USER_ADVISOR_TASKS
WHERE task_name ='tuning_sql_test';
TASK_NAME
STATUS
------------------------------ -----------
tuning_sql_test
COMPLETED
第四步:查看优化结果
通过dbms_sqltune.report_tuning_task函数可以获得优化任务的结果。
SQL> SET LONG 999999
SQL> set serveroutput on size 999999
SQL> SET LINESIZE 100
SQL> SELECT DBMS_SQLTUNE.REPORT_TUNING_TASK(
'tuning_sql_test') from DUAL;
DBMS_SQLTUNE.REPORT_TUNING_TASK('TUNING_SQL_TEST')
----------------------------------------------------------------------------------------------------
GENERAL INFORMATION SECTION
-------------------------------------------------------------------------------
Tuning Task
Name
: tuning_sql_test
Tuning Task
Owner
: DEMO
Scope
: COMPREHENSIVE
Time
Limit(seconds)
: 60
Completion
Status
: COMPLETED
Started
at
: 5/28/2010 13:16:43
Completed
at
: 5/28/2010 13:16:44
Number of Index
Findings
: 1
Schema Name: DEMO
SQL
ID
: 6p64dnnsqf9pm
SQL Text : select count(*) from
bigtab a, smalltab b where a.object_name=b.table_name
-------------------------------------------------------------------------------
FINDINGS SECTION (1 finding)
-------------------------------------------------------------------------------
1- 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: 100%)
----------------------------------------
- Consider running the Access Advisor to improve
the physical schema design or creating the recommended index.
create index
DEMO.IDX$$_06C50001 on SYS.SMALLTAB('TABLE_NAME');
- Consider running the Access Advisor to improve
the physical schema design or creating the recommended index.
create index
DEMO.IDX$$_06C50002 on SYS.BIGTAB('OBJECT_NAME');
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.
EXPLAIN PLANS SECTION
-------------------------------------------------------------------------------
1- Original
-----------
Plan hash value: 3089226980
--------------------------------------------------------------------------------
| Id |
Operation
|
Name
| Rows | Bytes | Cost (%CPU)|
Time
|
--------------------------------------------------------------------------------
| 0 | SELECT
STATEMENT
|
|
1 | 36
| 3550 (2)|
00:00:43 |
| 1 | SORT
AGGREGATE
|
|
1 | 36
|
|
|
|* 2 | HASH
JOIN
|
| 155K|
5462K| 3550
(2)| 00:00:43 |
| 3
| TABLE
ACCESS FULL| SMALLTAB | 1223 | 22014
|
11 (0)| 00:00:01 |
| 4
| TABLE
ACCESS FULL| BIGTAB
|
1205K|
20M| 3526
(1)| 00:00:43 |
--------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
2 -
access("A"."OBJECT_NAME"="B"."TABLE_NAME")
2- Using New Indices
--------------------
Plan hash value: 494801882
-----------------------------------------------------------------------------------------
| Id |
Operation
|
Name
| Rows | Bytes | Cost (%CPU)|
Time
|
-----------------------------------------------------------------------------------------
| 0 | SELECT
STATEMENT
|
|
1 | 36
| 1108 (3)|
00:00:14 |
| 1 | SORT
AGGREGATE
|
|
1 | 36
|
|
|
|* 2 | HASH
JOIN
|
| 155K|
5462K| 1108
(3)| 00:00:14 |
| 3
| INDEX FAST
FULL SCAN| IDX$$_06C50001 | 1223 | 22014
|
3 (0)| 00:00:01 |
| 4
| INDEX FAST
FULL SCAN| IDX$$_06C50002 |
1205K|
20M| 1093
(2)| 00:00:14 |
-----------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
2 -
access("A"."OBJECT_NAME"="B"."TABLE_NAME")
------------------------------------------------------------------------------
看一下这个优化建议报告:
第一部分是关于这次优化任务的基本信息:如任务名称、执行时间、范围、涉及到的语句等等。
第二部分是关于这次优化任务的所找到的问题以及给出的优化建议。前面先给出了问题描述:可以通过建立更多的索引来提高性能;然后是建议的具体内容:在表smalltab的字段table_name上创建索引,在表bigtab的字段object_name上创建索引;最后是相关注意事项:此次优化虽然给出了创建索引的建议,但是最好通过SQL访问建议器(SQL
Access Advisor
SAA)结合整个数据库的工作量来深入分析,那样就能给出考虑了索引维护和空间消耗等因素的更加合理的建议。
最后,报告还给出了原有的查询计划,以及采用优化建议以后的查询计划的对比。可以看出COST值大大下降。
五、删除优化任务
通过调用dbms_sqltune.drop_tuning_task可以删除已经存在的优化任务
SQL>exec
dbms_sqltune.drop_tuning_task('tuning_sql_test');
PL/SQL procedure successfully completed.
注: 整理自网络
转自:http://blog.csdn.net/tianlesoftware/article/details/5630888
在Oracle10g之前,优化SQL是个比较费力的技术活,不停的分析执行计划,加hint,分析统计信息等等。在10g中,Oracle推出了自己的SQL优化辅助工具:
SQL优化器(SQL Tuning Advisor
:STA),它是新的DBMS_SQLTUNE包。使用STA一定要保证优化器是CBO模式下。
执行DBMS_SQLTUNE包进行sql优化需要有advisor的权限:
SQL> create user dave identified by dave;
用户已创建。
SQL> grant connect,resource to dave;
授权成功。
SQL> grant advisor to dave;
授权成功。
下面简单介绍一下如何优化一条找到的问题语句。
create table bigtab as select rownum as "id",a.* from
sys.all_objects a;
create table smalltab as select rownum as "id", a.* FROM
sys.all_tables a;
然后多运行几次下面的脚本,增加表里的数据:
insert into bigtab select rownum as "id",a.* from sys.all_objects
a;
insert into smalltab select rownum as "id", a.* FROM sys.all_tables
a;
这里创建一张大表和一张小表,并且都没有索引,下面执行一个查询:
SQL> set timing on
SQL> set autot on
SQL> select count(*) from bigtab a, smalltab b where
a.object_name=b.table_name;
COUNT(*)
----------
2141537
已用时间: 00: 00: 20.05
执行计划
----------------------------------------------------------
Plan hash value: 3089226980
--------------------------------------------------------------------------------
| Id |
Operation
|
Name
| Rows | Bytes | Cost (%CPU)|
Time
|
--------------------------------------------------------------------------------
| 0 | SELECT
STATEMENT
|
|
1 | 45
| 3146 (1)|
00:00:38 |
| 1 | SORT
AGGREGATE
|
|
1 | 45
|
|
|
|* 2 | HASH
JOIN
|
|
447K|
19M| 3146
(1)| 00:00:38 |
| 3
| TABLE
ACCESS FULL| SMALLTAB | 27327 |
533K|
264 (1)| 00:00:04 |
| 4
| TABLE
ACCESS FULL| BIGTAB
|
712K|
16M| 2878
(1)| 00:00:35 |
--------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
2 -
access("A"."OBJECT_NAME"="B"."TABLE_NAME")
统计信息
----------------------------------------------------------
0 recursive calls
0 db block gets
31149 consistent gets
21058 physical reads
0 redo size
426 bytes sent via SQL*Net to client
416 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
1 rows processed
第一步:创建优化任务
通过调用函数CREATE_TUNING_TASK来创建优化任务,调用存储过程EXECUTE_TUNING_TASK执行该任务:
SQL> set autot off
SQL> set timing off
SQL> DECLARE
2
my_task_name VARCHAR2(30);
3
my_sqltext CLOB;
4 BEGIN
5 my_sqltext
:= 'select count(*) from bigtab a, smalltab b where
a.object_name=b.table_name';
6
my_task_name := DBMS_SQLTUNE.CREATE_TUNING_TASK(
7
sql_text
=> my_sqltext,
8
user_name =>
'DAVE', --
注意是大写,不然会报错,用户无效
9
scope
=> 'COMPREHENSIVE',
10
time_limit => 60,
11
task_name =>
'tuning_sql_test',
12
description => 'Task to tune a query on a specified
table');
13
14
DBMS_SQLTUNE.EXECUTE_TUNING_TASK( task_name =>
'tuning_sql_test');
15 END;
16 /
PL/SQL procedure successfully completed.
在函数CREATE_TUNING_TASK,sql_text是需要优化的语句,user_name是该语句通过哪个用户执行,scope是优化范围(limited或comprehensive),time_limit优化过程的时间限制,task_name优化任务名称,description优化任务描述。
第二步: 执行优化任务
通过调用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_sql_test');
PL/SQL 过程已成功完成。
第三步:检查优化任务的状态
通过查看user_advisor_tasks/dba_advisor_tasks视图可以查看优化任务的当前状态。
SQL> SELECT task_name,status FROM USER_ADVISOR_TASKS
WHERE task_name ='tuning_sql_test';
TASK_NAME
STATUS
------------------------------ -----------
tuning_sql_test
COMPLETED
第四步:查看优化结果
通过dbms_sqltune.report_tuning_task函数可以获得优化任务的结果。
SQL> SET LONG 999999
SQL> set serveroutput on size 999999
SQL> SET LINESIZE 100
SQL> SELECT DBMS_SQLTUNE.REPORT_TUNING_TASK(
'tuning_sql_test') from DUAL;
DBMS_SQLTUNE.REPORT_TUNING_TASK('TUNING_SQL_TEST')
----------------------------------------------------------------------------------------------------
GENERAL INFORMATION SECTION
-------------------------------------------------------------------------------
Tuning Task
Name
: tuning_sql_test
Tuning Task
Owner
: DEMO
Scope
: COMPREHENSIVE
Time
Limit(seconds)
: 60
Completion
Status
: COMPLETED
Started
at
: 5/28/2010 13:16:43
Completed
at
: 5/28/2010 13:16:44
Number of Index
Findings
: 1
Schema Name: DEMO
SQL
ID
: 6p64dnnsqf9pm
SQL Text : select count(*) from
bigtab a, smalltab b where a.object_name=b.table_name
-------------------------------------------------------------------------------
FINDINGS SECTION (1 finding)
-------------------------------------------------------------------------------
1- 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: 100%)
----------------------------------------
- Consider running the Access Advisor to improve
the physical schema design or creating the recommended index.
create index
DEMO.IDX$$_06C50001 on SYS.SMALLTAB('TABLE_NAME');
- Consider running the Access Advisor to improve
the physical schema design or creating the recommended index.
create index
DEMO.IDX$$_06C50002 on SYS.BIGTAB('OBJECT_NAME');
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.
EXPLAIN PLANS SECTION
-------------------------------------------------------------------------------
1- Original
-----------
Plan hash value: 3089226980
--------------------------------------------------------------------------------
| Id |
Operation
|
Name
| Rows | Bytes | Cost (%CPU)|
Time
|
--------------------------------------------------------------------------------
| 0 | SELECT
STATEMENT
|
|
1 | 36
| 3550 (2)|
00:00:43 |
| 1 | SORT
AGGREGATE
|
|
1 | 36
|
|
|
|* 2 | HASH
JOIN
|
| 155K|
5462K| 3550
(2)| 00:00:43 |
| 3
| TABLE
ACCESS FULL| SMALLTAB | 1223 | 22014
|
11 (0)| 00:00:01 |
| 4
| TABLE
ACCESS FULL| BIGTAB
|
1205K|
20M| 3526
(1)| 00:00:43 |
--------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
2 -
access("A"."OBJECT_NAME"="B"."TABLE_NAME")
2- Using New Indices
--------------------
Plan hash value: 494801882
-----------------------------------------------------------------------------------------
| Id |
Operation
|
Name
| Rows | Bytes | Cost (%CPU)|
Time
|
-----------------------------------------------------------------------------------------
| 0 | SELECT
STATEMENT
|
|
1 | 36
| 1108 (3)|
00:00:14 |
| 1 | SORT
AGGREGATE
|
|
1 | 36
|
|
|
|* 2 | HASH
JOIN
|
| 155K|
5462K| 1108
(3)| 00:00:14 |
| 3
| INDEX FAST
FULL SCAN| IDX$$_06C50001 | 1223 | 22014
|
3 (0)| 00:00:01 |
| 4
| INDEX FAST
FULL SCAN| IDX$$_06C50002 |
1205K|
20M| 1093
(2)| 00:00:14 |
-----------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
2 -
access("A"."OBJECT_NAME"="B"."TABLE_NAME")
------------------------------------------------------------------------------
看一下这个优化建议报告:
第一部分是关于这次优化任务的基本信息:如任务名称、执行时间、范围、涉及到的语句等等。
第二部分是关于这次优化任务的所找到的问题以及给出的优化建议。前面先给出了问题描述:可以通过建立更多的索引来提高性能;然后是建议的具体内容:在表smalltab的字段table_name上创建索引,在表bigtab的字段object_name上创建索引;最后是相关注意事项:此次优化虽然给出了创建索引的建议,但是最好通过SQL访问建议器(SQL
Access Advisor
SAA)结合整个数据库的工作量来深入分析,那样就能给出考虑了索引维护和空间消耗等因素的更加合理的建议。
最后,报告还给出了原有的查询计划,以及采用优化建议以后的查询计划的对比。可以看出COST值大大下降。
五、删除优化任务
通过调用dbms_sqltune.drop_tuning_task可以删除已经存在的优化任务
SQL>exec
dbms_sqltune.drop_tuning_task('tuning_sql_test');
PL/SQL procedure successfully completed.
注: 整理自网络
转自:http://blog.csdn.net/tianlesoftware/article/details/5630888
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