搜尋
首頁資料庫mysql教程oracle的存储提纲简介

从oracle 10g开始,oracle推出了存储提纲用来固定sql语句的执行计划,在oracle 11g后存储提纲被sql计划基线(sql plan baseline)取而代之,sql plan baseline也和存储提纲一样被用来提供稳定的执行计划,简单来讲也是固化sql语句执行计划的,而同样固化执行

从oracle 10g开始,oracle推出了存储提纲用来固定sql语句的执行计划,在oracle 11g后存储提纲被sql计划基线(sql plan baseline)取而代之,sql plan baseline也和存储提纲一样被用来提供稳定的执行计划,简单来讲也是固化sql语句执行计划的,而同样固化执行计划的还有hint、sql profile、存储提纲等,下面小鱼简单来对存储提纲和sql计划基线做一定的介绍。

Oracle stored outline(存储提纲)和sql计划基线最主要的作用就是用来保持固定sql语句的执行计划,让sql语句的执行计划在数据库环境变更(统计信息、优化器参数、表结果变更等)后还能保持原来的执行计划。

比如我们升降级数据库会由于优化器版本的不同造成执行计划差异、统计信息不准确导致执行计划可能出现波动、优化器的bug等造成执行计划不合理等,我们都可以采取oracle的存储提纲和sql计划基线来固化sql的执行计划。

下面来看看oracle的stored outline是如何工作的:
存储提纲是一个和sql语句相关的对象,存储在数据字典里的,优化器正是根据存储提纲关联的执行计划来固化sql语句执行计划。

首先对sql语句进行标准化,移除空白并转换非字段值的部分为大写,为标准化的sql语句计算一个签名。注意该签名是一个hash value,然后当发现相同签名的存储提纲时,就会去检查当前执行的sql语句和存储提纲记录的sql语句是否相同,如果相同则使用存储提纲内的执行计划。

关于创建存储提纲有两种方法,分别是自动创建和手动创建,自动创建需要结合初始化参数create_stored_outlines,手动创建可以用create outline或者dbms_outln.create_outline来创建。

这里小鱼主要来演示下手动创建存储提纲。

SQL> create table t_out01 as select * from dba_objects;

Table created.
SQL> create or replace outline outline01 for category outline on select object_name from t_out01 where object_id=1099;

Outline created.
SQL> select name,category,used,enabled,sql_text from user_outlines;

NAME CATEGORY USED ENABLED
------------------------------ ------------------------------ ------ --------
SQL_TEXT
--------------------------------------------------------------------------------
OUTLINE01 OUTLINE UNUSED ENABLED
select object_name from t_out01 where object_id=1099

SQL> select hint from user_outline_hints where name='OUTLINE01';

HINT
--------------------------------------------------------------------------------
FULL(@"SEL$1" "T_OUT01"@"SEL$1")
OUTLINE_LEAF(@"SEL$1")
ALL_ROWS
OPT_PARAM('_push_join_union_view' 'false')
OPT_PARAM('_push_join_predicate' 'false')
OPTIMIZER_FEATURES_ENABLE('10.2.0.4')
IGNORE_OPTIM_EMBEDDED_HINTS

7 rows selected.

SQL> alter system set use_stored_outlines=OUTLINE;

System altered.

SQL> select object_name from t_out01 where object_id=1099;

OBJECT_NAME
--------------------------------------------------------------------------------------------------------------------------------
V$PARAMETER

SQL> set linesize 140
SQL> select * from table(dbms_xplan.display_cursor(null,null));

PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------------------------------------------------------------------
SQL_ID a5fdfsf61dk3f, child number 0
-------------------------------------
select object_name from t_out01 where object_id=1099

Plan hash value: 43222384

-----------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
-----------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | | | 234 (100)| |
|* 1 | TABLE ACCESS FULL| T_OUT01 | 1 | 26 | 234 (1)| 00:00:03 |

PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------------------------------------------------------------------
-----------------------------------------------------------------------------

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

1 - filter("OBJECT_ID"=1099)

18 rows selected.

SQL> create index ind_obj_id on t_out01(object_id);

Index created.
SQL> select object_name from t_out01 where object_id=1099;

OBJECT_NAME
--------------------------------------------------------------------------------------------------------------------------------
V$PARAMETER

Execution Plan
----------------------------------------------------------
Plan hash value: 2483087502

------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 26 | 2 (0)| 00:00:01 |
| 1 | TABLE ACCESS BY INDEX ROWID| T_OUT01 | 1 | 26 | 2 (0)| 00:00:01 |
|* 2 | INDEX RANGE SCAN | IND_OBJ_ID | 1 | | 1 (0)| 00:00:01 |
------------------------------------------------------------------------------------------

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

2 - access("OBJECT_ID"=1099)

这个数据库版本是linux的10.2.0.4.0的版本,又尝试了windows的一个10.2.0.4.0版本的数据库,结果还是如此,就是创建的outline优化器并不去使用它,刚开始小鱼觉得可能是否和bug有关的,于是换了一个11.2.0.1的库还是如此,群里的一个热情的朋友测试存储提纲也没问题,人品真的很有点差啊,不过对于这类问题我们可不能就直接扔到一边去,小鱼一直坚信能遇见就是幸运的。

对于上述测试小鱼均都是使用的sys用户测试的,我们换一个用户来试试看
SQL> show user;
USER is "XIAOYU"
SQL> create table t_out01 as select * from dba_objects;

Table created.
SQL> create or replace outline outline1 for category cate on select object_name
from t_out01 where object_id=1009;

Outline created.
SQL> set autotrace on exp
SQL> set linesize 140;
SQL> select object_name from t_out01 where object_id=1009;

OBJECT_NAME
--------------------------------------------------------------------------------
------------------------------------------------
V$LOG

Execution Plan
----------------------------------------------------------
Plan hash value: 43222384

-----------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
-----------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 8 | 632 | 158 (1)| 00:00:02 |
|* 1 | TABLE ACCESS FULL| T_OUT01 | 8 | 632 | 158 (1)| 00:00:02 |
-----------------------------------------------------------------------------

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

1 - filter("OBJECT_ID"=1009)

Note
-----
- dynamic sampling used for this statement

SQL> set autotrace off
SQL> select name,category,used,sql_text from user_outlines;

NAME CATEGORY USED
------------------------------ ------------------------------ ------
SQL_TEXT
--------------------------------------------------------------------------------

OUTLINE1 CATE UNUSED
select object_name from t_out01 where object_id=1009

SQL> alter session set use_stored_outlines=cate;

Session altered.
SQL> set autotrace on exp
SQL> select object_name from t_out01 where object_id=1009;

OBJECT_NAME
--------------------------------------------------------------------------------
------------------------------------------------
V$LOG

Execution Plan
----------------------------------------------------------
Plan hash value: 43222384

-----------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
-----------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 581 | 45899 | 158 (1)| 00:00:02 |
|* 1 | TABLE ACCESS FULL| T_OUT01 | 581 | 45899 | 158 (1)| 00:00:02 |
-----------------------------------------------------------------------------

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

1 - filter("OBJECT_ID"=1009)

Note
-----
- outline "OUTLINE1" used for this statement

看出这里的note表示已经使用了outline OUTLINE1,下面我们建立索引
SQL> create index indid on t_out01(object_id);

Index created.
SQL> select object_name from t_out01 where object_id=1009;

OBJECT_NAME
--------------------------------------------------------------------------------
------------------------------------------------
V$LOG

Execution Plan
----------------------------------------------------------
Plan hash value: 1679505401

--------------------------------------------------------------------------------
-------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Tim
e |
--------------------------------------------------------------------------------
-------
| 0 | SELECT STATEMENT | | 581 | 45899 | 4 (0)| 00:
00:01 |
| 1 | TABLE ACCESS BY INDEX ROWID| T_OUT01 | 581 | 45899 | 4 (0)| 00:
00:01 |
|* 2 | INDEX RANGE SCAN | INDID | 232 | | 1 (0)| 00:
00:01 |
--------------------------------------------------------------------------------
-------
Predicate Information (identified by operation id):
---------------------------------------------------

2 - access("OBJECT_ID"=1009)

Note
-----
- outline "OUTLINE1" used for this statement
但是建议索引后,执行计划好像还是变化了,从之前的全表扫描变为了索引扫描。
SQL> set autotrace off
SQL> select name,category,used,sql_text from user_outlines;

NAME CATEGORY USED
------------------------------ ------------------------------ ------
SQL_TEXT
--------------------------------------------------------------------------------

OUTLINE1 CATE USED
select object_name from t_out01 where object_id=1009

SQL> select hint from dba_outline_hints where name='OUTLINE1';

HINT
--------------------------------------------------------------------------------
FULL(@"SEL$1" "T_OUT01"@"SEL$1")
OUTLINE_LEAF(@"SEL$1")
ALL_ROWS
OPTIMIZER_FEATURES_ENABLE('10.2.0.4')
IGNORE_OPTIM_EMBEDDED_HINTS

防止set autotrace的执行计划不准,我们用dbms_xplan.display_cursor看看真实的执行计划
SQL> select * from table(dbms_xplan.display_cursor(null,null));

PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
------------------------------------------------------------
SQL_ID 7k0h3uvq0xufh, child number 0
-------------------------------------
select object_name from t_out01 where object_id=1009

Plan hash value: 1679505401

--------------------------------------------------------------------------------
-------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Tim
e |
--------------------------------------------------------------------------------
-------
| 0 | SELECT STATEMENT | | | | 4 (100)|
|
| 1 | TABLE ACCESS BY INDEX ROWID| T_OUT01 | 581 | 45899 | 4 (0)| 00:
00:01 |
|* 2 | INDEX RANGE SCAN | INDID | 232 | | 1 (0)| 00:
00:01 |
--------------------------------------------------------------------------------
-------

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

2 - access("OBJECT_ID"=1009)

Note
-----
- outline "OUTLINE1" used for this statement
Note是显示使用了outline outline1,但是执行计划依然还是索引扫描,而我们查看outline outline1对应的hint中还是原来的全表扫描的执行计划,对于这个问题问了一些朋友,都没有合适的答案。

首先这里我们确定了stored outline对于sys用户无效,这个还没有找到合适的资料和文档来说明,第二个是10.2.0.4版本的数据库,虽然执行计划提示使用了存储提纲,但是执行计划确没有使用stored outline的执行计划,找了半天在mos上发现了一篇关于stored outline的bug ,有兴趣的朋友可以试试打patch看看!
Bug 6455659 - Stored outlines do not work in multibyte DB

而在oracle性能诊断艺术那本书中也提到了即使是使用了存储提纲,执行计划依然可能变化,也正是这个原因,存储提纲很少在生产环境中大批量的使用。

小鱼再找来一个11.2.0.1的数据库来进行存储提纲的测试:
SQL> select * from v$version;

BANNER
--------------------------------------------------------------------------------
Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - 64bit Production
PL/SQL Release 11.2.0.1.0 - Production
CORE 11.2.0.1.0 Production
TNS for Linux: Version 11.2.0.1.0 - Production
NLSRTL Version 11.2.0.1.0 - Production

SQL> create table t as select * from dba_objects;

Table created.

SQL> create or replace outline outline01 for category cate on select object_name from t where object_id=1090;

Outline created.

SQL> show user;
USER is "TEST"
SQL> set autotrace on exp
SQL> set linesize 140
SQL> select object_name from t where object_id=1090;

OBJECT_NAME
--------------------------------------------------------------------------------------------------------------------------------
SYS_LOB0000001087C00012$$

Execution Plan
----------------------------------------------------------
Plan hash value: 1601196873

--------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
--------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 12 | 948 | 299 (1)| 00:00:04 |
|* 1 | TABLE ACCESS FULL| T | 12 | 948 | 299 (1)| 00:00:04 |
--------------------------------------------------------------------------

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

1 - filter("OBJECT_ID"=1090)

Note
-----
- dynamic sampling used for this statement (level=2)

SQL> create index ind_id on t(object_id);

Index created.

SQL> select object_name from t where object_id=1090;

OBJECT_NAME
--------------------------------------------------------------------------------------------------------------------------------
SYS_LOB0000001087C00012$$

Execution Plan
----------------------------------------------------------
Plan hash value: 4043158466

--------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
--------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 79 | 2 (0)| 00:00:01 |
| 1 | TABLE ACCESS BY INDEX ROWID| T | 1 | 79 | 2 (0)| 00:00:01 |
|* 2 | INDEX RANGE SCAN | IND_ID | 1 | | 1 (0)| 00:00:01 |
--------------------------------------------------------------------------------------

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

2 - access("OBJECT_ID"=1090)

Note
-----
- dynamic sampling used for this statement (level=2)

SQL> alter system set use_stored_outlines=cate;

System altered.

SQL> select object_name from t where object_id=1090;

OBJECT_NAME
--------------------------------------------------------------------------------------------------------------------------------
SYS_LOB0000001087C00012$$

Execution Plan
----------------------------------------------------------
Plan hash value: 1601196873

--------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
--------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 895 | 70705 | 300 (1)| 00:00:04 |
|* 1 | TABLE ACCESS FULL| T | 895 | 70705 | 300 (1)| 00:00:04 |
--------------------------------------------------------------------------

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

1 - filter("OBJECT_ID"=1090)

Note
-----
- outline "OUTLINE01" used for this statement

SQL> alter session set use_stored_outlines=false;

Session altered.

SQL> select object_name from t where object_id=1090;

OBJECT_NAME
--------------------------------------------------------------------------------------------------------------------------------
SYS_LOB0000001087C00012$$

Execution Plan
----------------------------------------------------------
Plan hash value: 4043158466

--------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
--------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 79 | 2 (0)| 00:00:01 |
| 1 | TABLE ACCESS BY INDEX ROWID| T | 1 | 79 | 2 (0)| 00:00:01 |
|* 2 | INDEX RANGE SCAN | IND_ID | 1 | | 1 (0)| 00:00:01 |
--------------------------------------------------------------------------------------

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

2 - access("OBJECT_ID"=1090)

Note
-----
- dynamic sampling used for this statement (level=2)

此时我们发现同样的测试在11.2.0.1上面则优化器使用了outline记录的hint 全表扫描,小鱼又找了几个10.2.0.4的库都是上述的情况,而这个测试更加给我们一个清晰的认识,就是一般而言我们不要在生产环境中大量使用存储提纲,即使设置了优化器也可能稀里糊涂的不去用outline的执行计划。

还有一种手动创建存储提纲的办法就是利用dbms_outln.create_outline 来创建存储提纲,dbms_outln包还有很多关于outline的procedure和function,有兴趣的同学可以倒腾下

SQL> desc dbms_outln;
PROCEDURE CREATE_OUTLINE
Argument Name Type In/Out Default?
------------------------------ ----------------------- ------ --------
HASH_VALUE NUMBER IN
CHILD_NUMBER NUMBER IN
CATEGORY VARCHAR2 IN DEFAULT

SQL> drop table t;

Table dropped.

SQL> create table t as select * from dba_objects;

Table created.

SQL> select object_name,object_type from t where object_id=1099;

OBJECT_NAME
--------------------------------------------------------------------------------
OBJECT_TYPE
-------------------
LOGMNR_SESSION_PK
INDEX

SQL> select hash_value from v$sql where sql_text like 'select object_name,object_type from t where object_id=1099%';

HASH_VALUE
----------
300252238

SQL> declare
2 begin
3 dbms_outln.create_outline(
4 hash_value=>300252238,
5 child_number=>0);
6 end;
7 /
declare
*
ERROR at line 1:
ORA-16953: Type of SQL statement not supported.
ORA-06512: at "SYS.OUTLN_PKG", line 324
ORA-06512: at "SYS.OUTLN_PKG", line 368
ORA-06512: at line 3

这里又报出错误了,查了半天资料没有发现一个合理的说法,现在测试的版本是11.2.0.1,而在别的版本中dbms_outln.create_outline是可以创建cache cursor的stored outline的,小鱼个人推断这个又可能是个bug,测试这个运气确实有点背

上面介绍了手动收集,下面简单来讲下自动收集,自动收集outline需要一个很重要的参数就是create_stored_outlines

SQL> create table t_auto01 as select * from dba_objects;

Table created.

SQL> alter session set create_stored_outlines=true;

Session altered.

SQL> select object_name from t_auto01 where object_id=1000;

OBJECT_NAME
--------------------------------------------------------------------------------------------------------------------------------
EXPACT$

SQL> select object_name from t_auto01 where object_id=1001;

OBJECT_NAME
--------------------------------------------------------------------------------------------------------------------------------
NOEXP$

SQL> alter session set create_stored_outlines=false;

Session altered.

SQL> create index ind_auto_id on t_auto01(object_id);

Index created.

SQL> select name,category,used,sql_text from user_outlines;

NAME CATEGORY USED
------------------------------ ------------------------------ ------
SQL_TEXT
--------------------------------------------------------------------------------
SYS_OUTLINE_14061917391589506 DEFAULT UNUSED
SELECT /* OPT_DYN_SAMP */ /*+ ALL_ROWS IGNORE_WHERE_CLAUSE NO_PARALLEL(SAMPLESUB

SYS_OUTLINE_14061917391589305 DEFAULT UNUSED
select object_name from t_auto01 where object_id=1000

SYS_OUTLINE_14061917393895607 DEFAULT UNUSED
select object_name from t_auto01 where object_id=1001

这里设置create_stored_outlines=true后,默认这个session就开始收集sql语句并创建对应的outlines
SQL> set autotrace on exp
SQL> select object_name from t_auto01 where object_id=1000;

OBJECT_NAME
--------------------------------------------------------------------------------------------------------------------------------
EXPACT$

Execution Plan
----------------------------------------------------------
Plan hash value: 2314754062

-------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
-------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 79 | 2 (0)| 00:00:01 |
| 1 | TABLE ACCESS BY INDEX ROWID| T_AUTO01 | 1 | 79 | 2 (0)| 00:00:01 |
|* 2 | INDEX RANGE SCAN | IND_AUTO_ID | 1 | | 1 (0)| 00:00:01 |
-------------------------------------------------------------------------------------------

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

2 - access("OBJECT_ID"=1000)

Note
-----
- dynamic sampling used for this statement (level=2)

SQL> alter session set use_stored_outlines=true;

Session altered.

SQL> select object_name from t_auto01 where object_id=1000;

OBJECT_NAME
--------------------------------------------------------------------------------------------------------------------------------
EXPACT$

Execution Plan
----------------------------------------------------------
Plan hash value: 795571617

------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 895 | 70705 | 300 (1)| 00:00:04 |
|* 1 | TABLE ACCESS FULL| T_AUTO01 | 895 | 70705 | 300 (1)| 00:00:04 |
------------------------------------------------------------------------------

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

1 - filter("OBJECT_ID"=1000)

Note
-----
- outline "SYS_OUTLINE_14061917391589305" used for this statement

SQL> select object_name from t_auto01 where object_id=1001;

OBJECT_NAME
--------------------------------------------------------------------------------------------------------------------------------
NOEXP$

Execution Plan
----------------------------------------------------------
Plan hash value: 795571617

------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 895 | 70705 | 300 (1)| 00:00:04 |
|* 1 | TABLE ACCESS FULL| T_AUTO01 | 895 | 70705 | 300 (1)| 00:00:04 |
------------------------------------------------------------------------------

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

1 - filter("OBJECT_ID"=1001)

Note
-----
- outline "SYS_OUTLINE_14061917393895607" used for this statement

SQL> select object_name from t_auto01 where object_id=1002;

OBJECT_NAME
--------------------------------------------------------------------------------------------------------------------------------
EXPPKGOBJ$

Execution Plan
----------------------------------------------------------
Plan hash value: 2314754062

-------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
-------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 79 | 2 (0)| 00:00:01 |
| 1 | TABLE ACCESS BY INDEX ROWID| T_AUTO01 | 1 | 79 | 2 (0)| 00:00:01 |
|* 2 | INDEX RANGE SCAN | IND_AUTO_ID | 1 | | 1 (0)| 00:00:01 |
-------------------------------------------------------------------------------------------

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

2 - access("OBJECT_ID"=1002)

Note
-----
- dynamic sampling used for this statement (level=2)

这里最后一个sql语句由于sql_text不相同,所以没有配对的outline hint可供使用。

而如果是针对一类sql语句,我们不太可能每个去创建outline,可以针对该sql改成bind value然后直接对bind后的sql创建outline
SQL> variable v_id number;
SQL> exec :v_id:=10000;

PL/SQL procedure successfully completed.

SQL> create outline outline02 on select object_name,object_type from t where object_id=:v_id;

Outline created.
SQL> select name,category,used,sql_text from user_outlines where name='OUTLINE02';

NAME CATEGORY USED
------------------------------ ------------------------------ ------
SQL_TEXT
--------------------------------------------------------------------------------
OUTLINE02 DEFAULT UNUSED
select object_name,object_type from t where object_id=:v_id

下面创建了object_id上的索引
SQL> create index ind_id on t(object_id);

Index created.
SQL> alter session set use_stored_outlines=false;

Session altered.

SQL> select object_name,object_type from t where object_id=:v_id;

OBJECT_NAME
--------------------------------------------------------------------------------------------------------------------------------
OBJECT_TYPE
-------------------
KU$_EQNTABLE_BYTES_ALLOC_VIEW
VIEW

Execution Plan
----------------------------------------------------------
Plan hash value: 4043158466

--------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
--------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 855 | 76950 | 6 (0)| 00:00:01 |
| 1 | TABLE ACCESS BY INDEX ROWID| T | 855 | 76950 | 6 (0)| 00:00:01 |
|* 2 | INDEX RANGE SCAN | IND_ID | 342 | | 1 (0)| 00:00:01 |
--------------------------------------------------------------------------------------

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

2 - access("OBJECT_ID"=TO_NUMBER(:V_ID))

Note
-----
- dynamic sampling used for this statement (level=2)

当设置use_stored_outlines=true后,优化器采取的outline中的执行计划。
SQL> alter session set use_stored_outlines=true;

Session altered.

SQL> select object_name,object_type from t where object_id=:v_id;

OBJECT_NAME
--------------------------------------------------------------------------------------------------------------------------------
OBJECT_TYPE
-------------------
KU$_EQNTABLE_BYTES_ALLOC_VIEW
VIEW

Execution Plan
----------------------------------------------------------
Plan hash value: 1601196873

--------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
--------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 895 | 80550 | 300 (1)| 00:00:04 |
|* 1 | TABLE ACCESS FULL| T | 895 | 80550 | 300 (1)| 00:00:04 |
--------------------------------------------------------------------------

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

1 - filter("OBJECT_ID"=TO_NUMBER(:V_ID))

Note
-----
- outline "OUTLINE02" used for this statement

陳述
本文內容由網友自願投稿,版權歸原作者所有。本站不承擔相應的法律責任。如發現涉嫌抄襲或侵權的內容,請聯絡admin@php.cn
MySQL的許可與其他數據庫系統相比如何?MySQL的許可與其他數據庫系統相比如何?Apr 25, 2025 am 12:26 AM

MySQL使用的是GPL許可證。 1)GPL許可證允許自由使用、修改和分發MySQL,但修改後的分發需遵循GPL。 2)商業許可證可避免公開修改,適合需要保密的商業應用。

您什麼時候選擇InnoDB而不是Myisam,反之亦然?您什麼時候選擇InnoDB而不是Myisam,反之亦然?Apr 25, 2025 am 12:22 AM

選擇InnoDB而不是MyISAM的情況包括:1)需要事務支持,2)高並發環境,3)需要高數據一致性;反之,選擇MyISAM的情況包括:1)主要是讀操作,2)不需要事務支持。 InnoDB適合需要高數據一致性和事務處理的應用,如電商平台,而MyISAM適合讀密集型且無需事務的應用,如博客系統。

在MySQL中解釋外鍵的目的。在MySQL中解釋外鍵的目的。Apr 25, 2025 am 12:17 AM

在MySQL中,外鍵的作用是建立表與表之間的關係,確保數據的一致性和完整性。外鍵通過引用完整性檢查和級聯操作維護數據的有效性,使用時需注意性能優化和避免常見錯誤。

MySQL中有哪些不同類型的索引?MySQL中有哪些不同類型的索引?Apr 25, 2025 am 12:12 AM

MySQL中有四種主要的索引類型:B-Tree索引、哈希索引、全文索引和空間索引。 1.B-Tree索引適用於範圍查詢、排序和分組,適合在employees表的name列上創建。 2.哈希索引適用於等值查詢,適合在MEMORY存儲引擎的hash_table表的id列上創建。 3.全文索引用於文本搜索,適合在articles表的content列上創建。 4.空間索引用於地理空間查詢,適合在locations表的geom列上創建。

您如何在MySQL中創建索引?您如何在MySQL中創建索引?Apr 25, 2025 am 12:06 AM

toCreateAnIndexinMysql,usethecReateIndexStatement.1)forasingLecolumn,使用“ createIndexIdx_lastNameEnemployees(lastName); 2)foracompositeIndex,使用“ createIndexIndexIndexIndexIndexDx_nameOmplayees(lastName,firstName,firstName);” 3)forauniqe instex,creationexexexexex,

MySQL與Sqlite有何不同?MySQL與Sqlite有何不同?Apr 24, 2025 am 12:12 AM

MySQL和SQLite的主要區別在於設計理念和使用場景:1.MySQL適用於大型應用和企業級解決方案,支持高性能和高並發;2.SQLite適合移動應用和桌面軟件,輕量級且易於嵌入。

MySQL中的索引是什麼?它們如何提高性能?MySQL中的索引是什麼?它們如何提高性能?Apr 24, 2025 am 12:09 AM

MySQL中的索引是數據庫表中一列或多列的有序結構,用於加速數據檢索。 1)索引通過減少掃描數據量提升查詢速度。 2)B-Tree索引利用平衡樹結構,適合範圍查詢和排序。 3)創建索引使用CREATEINDEX語句,如CREATEINDEXidx_customer_idONorders(customer_id)。 4)複合索引可優化多列查詢,如CREATEINDEXidx_customer_orderONorders(customer_id,order_date)。 5)使用EXPLAIN分析查詢計劃,避

說明如何使用MySQL中的交易來確保數據一致性。說明如何使用MySQL中的交易來確保數據一致性。Apr 24, 2025 am 12:09 AM

在MySQL中使用事務可以確保數據一致性。 1)通過STARTTRANSACTION開始事務,執行SQL操作後用COMMIT提交或ROLLBACK回滾。 2)使用SAVEPOINT可以設置保存點,允許部分回滾。 3)性能優化建議包括縮短事務時間、避免大規模查詢和合理使用隔離級別。

See all articles

熱AI工具

Undresser.AI Undress

Undresser.AI Undress

人工智慧驅動的應用程序,用於創建逼真的裸體照片

AI Clothes Remover

AI Clothes Remover

用於從照片中去除衣服的線上人工智慧工具。

Undress AI Tool

Undress AI Tool

免費脫衣圖片

Clothoff.io

Clothoff.io

AI脫衣器

Video Face Swap

Video Face Swap

使用我們完全免費的人工智慧換臉工具,輕鬆在任何影片中換臉!

熱工具

SublimeText3 Mac版

SublimeText3 Mac版

神級程式碼編輯軟體(SublimeText3)

SecLists

SecLists

SecLists是最終安全測試人員的伙伴。它是一個包含各種類型清單的集合,這些清單在安全評估過程中經常使用,而且都在一個地方。 SecLists透過方便地提供安全測試人員可能需要的所有列表,幫助提高安全測試的效率和生產力。清單類型包括使用者名稱、密碼、URL、模糊測試有效載荷、敏感資料模式、Web shell等等。測試人員只需將此儲存庫拉到新的測試機上,他就可以存取所需的每種類型的清單。

SublimeText3 英文版

SublimeText3 英文版

推薦:為Win版本,支援程式碼提示!

Atom編輯器mac版下載

Atom編輯器mac版下載

最受歡迎的的開源編輯器

禪工作室 13.0.1

禪工作室 13.0.1

強大的PHP整合開發環境