如何使用dbms_xplan查看执行计划

发布时间：2021-11-09 10:03:26 来源：亿速云阅读：163 作者：小新栏目：关系型数据库

小编给大家分享一下如何使用dbms_xplan查看执行计划，相信大部分人都还不怎么了解，因此分享这篇文章给大家参考一下，希望大家阅读完这篇文章后大有收获，下面让我们一起去了解一下吧！

概述

dbms_xplan包提供了多样的，预定义的方式去解释执行计划。sql执行计划，执行时间等信息都存储与v$sql_plan,v$sql_plan_statistics_all视图中。此包运行的权限是执行用户，不是包的拥有者sys。

当执行diplay_awr时，需要DBA_HIST_SQL_PLAN, DBA_HIST_SQLTEXT, and V$DATABASE的查询权限

当执行display_cursor时需要V$SQL_PLAN, V$SESSION and V$SQL_PLAN_STATISTICS_ALL的查询权限

当执行display_sql_plan_baseline时，需要DBA_SQL_PLAN_BASELINES的查询权限

当执行display_sqlset时，需要ALL_SQLSET_STATEMENTS and ALL_SQLSET_PLANS的查询权限

以上的所有权限都在SELECT_CATALOG角色中，所以直接赋权SELECT_CATALOG就可以了。

dbms_xplan中有许多功能，我这里着重研究其中几个常用的

SQL> desc dbms_xplan;

…

FUNCTION DISPLAY_AWR RETURNS DBMS_XPLAN_TYPE_TABLE

Argument Name Type In/Out Default?

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

SQL_ID VARCHAR2 IN

PLAN_HASH_VALUE NUMBER(38) IN DEFAULT

DB_ID NUMBER(38) IN DEFAULT

FORMAT VARCHAR2 IN DEFAULT

FUNCTION DISPLAY_CURSOR RETURNS DBMS_XPLAN_TYPE_TABLE

Argument Name Type In/Out Default?

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

SQL_ID VARCHAR2 IN DEFAULT

CURSOR_CHILD_NO NUMBER(38) IN DEFAULT

FORMAT VARCHAR2 IN DEFAULT

FUNCTION DISPLAY_PLAN RETURNS CLOB

Argument Name Type In/Out Default?

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

TABLE_NAME VARCHAR2 IN DEFAULT

STATEMENT_ID VARCHAR2 IN DEFAULT

FORMAT VARCHAR2 IN DEFAULT

FILTER_PREDS VARCHAR2 IN DEFAULT

TYPE VARCHAR2 IN DEFAULT

FUNCTION DISPLAY_SQLSET RETURNS DBMS_XPLAN_TYPE_TABLE

Argument Name Type In/Out Default?

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

SQLSET_NAME VARCHAR2 IN

SQL_ID VARCHAR2 IN

PLAN_HASH_VALUE NUMBER(38) IN DEFAULT

FORMAT VARCHAR2 IN DEFAULT

SQLSET_OWNER VARCHAR2 IN DEFAULT

FUNCTION DISPLAY_SQL_PLAN_BASELINE RETURNS DBMS_XPLAN_TYPE_TABLE

Argument Name Type In/Out Default?

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

SQL_HANDLE VARCHAR2 IN DEFAULT

PLAN_NAME VARCHAR2 IN DEFAULT

FORMAT VARCHAR2 IN DEFAULT

…

dbms_xplan.display

展示执行计划内容

简单的执行一次display

SQL> explain plan for insert into scott.emp values(1111,'xplan','','','','','','');

Explained.

SQL> select * from table(dbms_xplan.display);

7 rows selected.

Execution Plan

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

Plan hash value: 2137789089

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

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

| 0 | SELECT STATEMENT | | 8168 | 16336 | 29 (0)| 00:00:01 |

| 1 | COLLECTION ITERATOR PICKLER FETCH| DISPLAY | 8168 | 16336 | 29 (0)| 00:00:01 |

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

Statistics

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

1890 recursive calls

40 db block gets

3635 consistent gets

0 physical reads

0 redo size

1102 bytes sent via SQL*Net to client

523 bytes received via SQL*Net from client

2 SQL*Net roundtrips to/from client

38 sorts (memory)

0 sorts (disk)

7 rows processed

SQL> select * from scott.emp where empno=1111;

no rows selected

—explain plan for ，dbms_xplan.display都没有执行sql。explain plan for是产生sql的执行计划并保存在PLAN_TABLE表中，dbms_xplan.display从PLAN_TABLE中提取计划并展示出来。

定义

DBMS_XPLAN.DISPLAY(

table_name IN VARCHAR2 DEFAULT 'PLAN_TABLE',

statement_id IN VARCHAR2 DEFAULT NULL,

format IN VARCHAR2 DEFAULT 'TYPICAL',

filter_preds IN VARCHAR2 DEFAULT NULL);

table_name：指定的是计划的存储表表名（不是执行表的表名）。默认是PLAN_TABLE。

statement_id：指定计划的statement_id，如果没有指定，则该值为explain plan的statement_id , 如果没有expain plan，则该值为最近一次解释的执行计划。

format：解释计划的level

? BASIC: Displays the minimum information in the plan—the operation ID, the operation name and its option.展示最少的信息

? TYPICAL: This is the default. Displays the most relevant information in the plan (operation id, name and option, #rows, #bytes and optimizer cost). Pruning, parallel and predicate information are only displayed when applicable. Excludes only PROJECTION, ALIAS and REMOTE SQL information (see below).默认值

? SERIAL: Like TYPICAL except that the parallel information is not displayed, even if the plan executes in parallel.没有并发信息

? ALL: Maximum user level. Includes information displayed with the TYPICAL level with additional information (PROJECTION, ALIAS and information about REMOTE SQL if the operation is distributed).展示最多的信息，包含了分布式操作的远程sql执行信息

filter_preds：sql过滤，限制从计划表中返回的行。

dbms_xplan.display_awr

展示在awr中存储的sql的执行计划

定义

DBMS_XPLAN.DISPLAY_AWR(

sql_id IN VARCHAR2,

plan_hash_value IN NUMBER DEFAULT NULL,

db_id IN NUMBER DEFAULT NULL,

format IN VARCHAR2 DEFAULT TYPICAL);

sql_id:在dba_hist_sqltext中可以找到sql_id

plan_hash_value:sql执行计划的hash值。如果该值被忽略，则函数返回sql_id中的所有执行计划

db_id：database_id。如果不知道则该值为V$DATABASE视图中的database_id，也就是本地数据库。

format：与display类似。总共有4个level：BASIC，TYPICAL,SERIAL,ALL。

SQL> select * from scott.emp where rownum<=1;

EMPNO ENAME JOB MGR HIREDATE SAL COMM

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

DEPTNO

----------

7369 SMITH CLERK 7902 17-DEC-80 800

—手动生成快照

SQL> EXECUTE DBMS_WORKLOAD_REPOSITORY.CREATE_SNAPSHOT();

PL/SQL procedure successfully completed.

SQL> select sql_id,sql_text from dba_hist_sqltext where sql_text like '%rownum%';

SQL_ID

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

SQL_TEXT

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

6yzbcy3x0yr1j

insert into wrh$_dispatcher (snap_id, dbid, instance_number, name, serial#,

fsbqktj5vw6n9

select next_run_date, obj#, run_job, sch_job from (select decode(bitand(a.flags,

cv959u044n88s

select 1 from sys.aq$_subscriber_table where rownum < 2 and subscriber_id <> 0 a

…

SQL_ID

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

SQL_TEXT

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

bd3tcy3ar02px

select * from scott.emp where rownum<=1

7 rows selected.

SQL>

—指定awr中存在sql

SQL> select * from table(dbms_xplan.display_awr('bd3tcy3ar02px'));

PLAN_TABLE_OUTPUT

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

SQL_ID bd3tcy3ar02px

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

select * from scott.emp where rownum<=1

Plan hash value: 1973284518

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

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

| 0 | SELECT STATEMENT | | | | 2 (100)| |

| 1 | COUNT STOPKEY | | | | | |

PLAN_TABLE_OUTPUT

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

| 2 | TABLE ACCESS FULL| EMP | 15 | 1305 | 2 (0)| 00:00:01 |

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

Note

-----

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

18 rows selected.

SQL>

dbms_xplan.display_cursor

展示cursor中的执行计划

定义

DBMS_XPLAN.DISPLAY_CURSOR(

sql_id IN VARCHAR2 DEFAULT NULL,

cursor_child_no IN NUMBER DEFAULT 0,

format IN VARCHAR2 DEFAULT ‘TYPICAL');

sql_id

cursor_child_no:子游标标志。如果没有指定，则展示sql_id下的所有执行计划

format

默认值执行

SQL> select * from scott.emp where rownum<=2;

EMPNO ENAME JOB MGR HIREDATE SAL COMM

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

DEPTNO

----------

7369 SMITH CLERK 7902 17-DEC-80 800

7499 ALLEN SALESMAN 7698 20-FEB-81 1600 300

—默认查询了当前session最后一次执行sql

SQL> select * from table(dbms_xplan.display_cursor);

PLAN_TABLE_OUTPUT

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

SQL_ID 90ud69jbjz75c, child number 0

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

select * from scott.emp where rownum<=2

Plan hash value: 1973284518

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

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

| 0 | SELECT STATEMENT | | | | 2 (100)| |

|* 1 | COUNT STOPKEY | | | | | |

PLAN_TABLE_OUTPUT

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

| 2 | TABLE ACCESS FULL| EMP | 15 | 1305 | 2 (0)| 00:00:01 |

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

Predicate Information (identified by operation id):

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

1 - filter(ROWNUM<=2)

Note

-----

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

PLAN_TABLE_OUTPUT

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

23 rows selected.

SQL>

指定sql_id查找plan，首先要找到sql_id

SQL> select sql_id,sql_text from v$sqlarea where sql_text like '%rownum<=2%';

SQL_ID

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

SQL_TEXT

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

75gpskbx0uk8w

select sql_id,sql_text from v$sqlarea where sql_text like '%rownum<=2%'

90ud69jbjz75c

select * from scott.emp where rownum<=2

SQL> select * from table(dbms_xplan.display_cursor('90ud69jbjz75c'));

PLAN_TABLE_OUTPUT

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

SQL_ID 90ud69jbjz75c, child number 0

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

select * from scott.emp where rownum<=2

Plan hash value: 1973284518

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

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

| 0 | SELECT STATEMENT | | | | 2 (100)| |

|* 1 | COUNT STOPKEY | | | | | |

PLAN_TABLE_OUTPUT

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

| 2 | TABLE ACCESS FULL| EMP | 15 | 1305 | 2 (0)| 00:00:01 |

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

Predicate Information (identified by operation id):

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

1 - filter(ROWNUM<=2)

Note

-----

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

PLAN_TABLE_OUTPUT

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

23 rows selected.

SQL>

如果sql不在内存中，则不能通过cursor方式查询

SQL> select * from table(dbms_xplan.display_cursor('90ud69jbjz75c'));

PLAN_TABLE_OUTPUT

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

SQL_ID: 90ud69jbjz75c, child number: 0 cannot be found

这时就可以通过生成快照的方式从awr中查询plan

以上是“如何使用dbms_xplan查看执行计划”这篇文章的所有内容，感谢各位的阅读！相信大家都有了一定的了解，希望分享的内容对大家有所帮助，如果还想学习更多知识，欢迎关注亿速云行业资讯频道！

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如何使用dbms_xplan查看执行计划

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