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sql-查看执行计划的方法

sql执行计划：把SQL语句拆分为每个的操作步骤组合，按照一定的顺序执行得出结果，查看并看懂执行计划是调优的关键步骤

查看执行计划的方法

DBMS_XPLAN包
sql*plus AUTO trace
V$SQL_PLAN、DBA_HIST_SQL_PLAN
?/rdbms/admin/awrsqrpt.sql
工具类：toad、pl/SQL DEV
跟踪dump：10046,10053

大多数人比较喜欢用工具直接看，以下来说明这些方式的不同用处

一、DBMS_XPLAN包

10g以后可以查看AWR中的语句执行计划，也可以查看当前内存中游标的执行计划。

主要有以下五个方法：

DISPLAY - 格式化并显示plan table中内容，类似工具的F5（EXPLAIN PLAN FOR …）
DISPLAY_AWR -格式和显示存储在AWR中的SQL语句的执行计划。数据来源: DBA_HIST_SQL_PLAN,DBA_HIST_SQLTEXT
DISPLAY_CURSOR -格式和显示任何加载游标执行计划的内容。数据来源：V$SQL_PLAN和V$SQL_PLAN_STATISTICS_ALL
DISPLAY_SQL_PLAN_BASELINE - 显示一个或多个执行计划的SQL语句通过SQL handle 标识。数据来源：DBA_SQL_PLAN_BASELINES
DISPLAY_SQLSET - 格式和显示存储在sql调优集中的执行计划内容。数据来源：ALL_SQLSET_STATEMENTS、ALL_SQLSET_PLANS

最常用的DISPLAY_AWR和DISPLAY_CURSOR，来阐述具体的调用方式，显示的内容

（一）、DISPLAY_CURSOR

显示当前shared pool->library cache中的执行计划

DBMS_XPLAN.DISPLAY_CURSOR(
   sql_id            IN  VARCHAR2  DEFAULT  NULL,
   cursor_child_no   IN  NUMBER    DEFAULT  0, 
   format            IN  VARCHAR2  DEFAULT  'TYPICAL');

参数	说明（常用说明）
sql_id	SQL的唯一标识，取SELECT SQL_ID FROM V$SQL，为null的情况下，取上一条语句的执行计划
cursor_child_no	子游标的id号，为null，取出全部子游标的执行计划
format	输出格式化默认TYPICAL ADVANCED +PEEKED_BINDS `ALLSTATS`

例子查看

#默认格式输出select * from  table(dbms_xplan.display_cursor('bjqjt2dfvya84',null))

SQL_ID  bjqjt2dfvya84, child number 0
-------------------------------------
select *　from emp where empno=7521

Plan hash value: 2949544139

--------------------------------------------------------------------------------------
| Id  | Operation                   | Name   | Rows  | Bytes | Cost (%CPU)| Time     |
--------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT            |        |       |       |     1 (100)|          |
|   1 |  TABLE ACCESS BY INDEX ROWID| EMP    |     1 |    38 |     1   (0)| 00:00:01 |
|*  2 |   INDEX UNIQUE SCAN         | PK_EMP |     1 |       |     0   (0)|          |
--------------------------------------------------------------------------------------

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

   2 - access("EMPNO"=7521)

＃格式化为ADVANCED +PEEKED_BINDS
select * from  table(dbms_xplan.display_cursor('bjqjt2dfvya84',null,'ADVANCED +PEEKED_BINDS'))

SQL_ID  bjqjt2dfvya84, child number 0
-------------------------------------
select *　from emp where empno=7521

Plan hash value: 2949544139

--------------------------------------------------------------------------------------
| Id  | Operation                   | Name   | Rows  | Bytes | Cost (%CPU)| Time     |
--------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT            |        |       |       |     1 (100)|          |
|   1 |  TABLE ACCESS BY INDEX ROWID| EMP    |     1 |    38 |     1   (0)| 00:00:01 |
|*  2 |   INDEX UNIQUE SCAN         | PK_EMP |     1 |       |     0   (0)|          |
--------------------------------------------------------------------------------------

Query Block Name / Object Alias (identified by operation id):
-------------------------------------------------------------

   1 - SEL$1 / EMP@SEL$1
   2 - SEL$1 / EMP@SEL$1

Outline Data
-------------

  /*+
      BEGIN_OUTLINE_DATA
      IGNORE_OPTIM_EMBEDDED_HINTS
      OPTIMIZER_FEATURES_ENABLE('11.2.0.3')
      DB_VERSION('11.2.0.3')
      OPT_PARAM('optimizer_dynamic_sampling' 0)
      ALL_ROWS
      OUTLINE_LEAF(@"SEL$1")
      INDEX_RS_ASC(@"SEL$1" "EMP"@"SEL$1" ("EMP"."EMPNO"))
      END_OUTLINE_DATA
  */

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

   2 - access("EMPNO"=7521)

Column Projection Information (identified by operation id):
-----------------------------------------------------------

   1 - "EMPNO"[NUMBER,22], "EMP"."ENAME"[VARCHAR2,10],
       "EMP"."JOB"[VARCHAR2,9], "EMP"."MGR"[NUMBER,22], "EMP"."HIREDATE"[DATE,7],
       "EMP"."SAL"[NUMBER,22], "EMP"."COMM"[NUMBER,22], "EMP"."DEPTNO"[NUMBER,22]
   2 - "EMP".ROWID[ROWID,10], "EMPNO"[NUMBER,22]

＃格式化ALLSTATS
两种处理方式： * hint 'gather_plan_statistics' is used for the statement or
       * parameter 'statistics_level' is set to 'ALL', at session or system level
select /*+gather_plan_statistics*/  *　from emp where empno=7521

select * from  table(dbms_xplan.display_cursor('dvj95t2z1gh2a',null,'ALLSTATS'))

SQL_ID  dvj95t2z1gh2a, child number 0
-------------------------------------
select /*+gather_plan_statistics*/  *　from emp where empno=7521

Plan hash value: 2949544139

------------------------------------------------------------------------------------------------
| Id  | Operation                   | Name   | Starts | E-Rows | A-Rows |   A-Time   | Buffers |
------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT            |        |      1 |        |      1 |00:00:00.01 |       2 |
|   1 |  TABLE ACCESS BY INDEX ROWID| EMP    |      1 |      1 |      1 |00:00:00.01 |       2 |
|*  2 |   INDEX UNIQUE SCAN         | PK_EMP |      1 |      1 |      1 |00:00:00.01 |       1 |
------------------------------------------------------------------------------------------------

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

   2 - access("EMPNO"=7521)

A-ROW是实际的行数，E-ROW是优化器评估的

（二）、DISPLAY_AWR

显示AWR中的SQL的执行计划，对分析历史SQL慢的相当有帮组

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);

参数	常用说明
SQL_ID	SQL的唯一标识，取SELECT SQL_ID FROM DBA_HIST_SQLTEXT
PLAN_HASH_VALUE	指定SQL语句的PLAN_HASH_VALUE,忽略取全部的SQL_ID下的执行计划
DB_ID	默认取V$DATABASE.DATABASE_ID
FORMAT	输出格式化默认TYPICAL ADVANCED +PEEKED_BINDS

例子查看

#默认输出的格式
select * from  table(dbms_xplan.display_awr('bjqjt2dfvya84'));

SQL_ID bjqjt2dfvya84
--------------------
select *　from emp where empno=7521

Plan hash value: 2949544139

--------------------------------------------------------------------------------------
| Id  | Operation                   | Name   | Rows  | Bytes | Cost (%CPU)| Time     |
--------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT            |        |       |       |     1 (100)|          |
|   1 |  TABLE ACCESS BY INDEX ROWID| EMP    |     1 |    38 |     1   (0)| 00:00:01 |
|   2 |   INDEX UNIQUE SCAN         | PK_EMP |     1 |       |     0   (0)|          |
--------------------------------------------------------------------------------------


#通过格式化ADVANCED +PEEKED_BINDS
select * from  table(dbms_xplan.display_awr('bjqjt2dfvya84',FORMAT=>'ADVANCED +PEEKED_BINDS'));
SQL_ID bjqjt2dfvya84
--------------------
select *　from emp where empno=7521

Plan hash value: 2949544139

--------------------------------------------------------------------------------------
| Id  | Operation                   | Name   | Rows  | Bytes | Cost (%CPU)| Time     |
--------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT            |        |       |       |     1 (100)|          |
|   1 |  TABLE ACCESS BY INDEX ROWID| EMP    |     1 |    38 |     1   (0)| 00:00:01 |
|   2 |   INDEX UNIQUE SCAN         | PK_EMP |     1 |       |     0   (0)|          |
--------------------------------------------------------------------------------------

Query Block Name / Object Alias (identified by operation id):
-------------------------------------------------------------

   1 - SEL$1 / EMP@SEL$1
   2 - SEL$1 / EMP@SEL$1

Outline Data
-------------

  /*+
      BEGIN_OUTLINE_DATA
      IGNORE_OPTIM_EMBEDDED_HINTS
      OPTIMIZER_FEATURES_ENABLE('11.2.0.3')
      DB_VERSION('11.2.0.3')
      OPT_PARAM('optimizer_dynamic_sampling' 0)
      ALL_ROWS
      OUTLINE_LEAF(@"SEL$1")
      INDEX_RS_ASC(@"SEL$1" "EMP"@"SEL$1" ("EMP"."EMPNO"))
      END_OUTLINE_DATA
  */

二、sqlplus autotrace

scott@GULL> set autotrace
用法: SET AUTOT[RACE] {OFF | ON | TRACE[ONLY]} [EXP[LAIN]] [STAT[ISTICS]]

可以体现执行语句的执行计划和统计信息

scott@GULL> SET autotrace  trace
scott@GULL> select *　from emp where empno=7521;


执行计划
----------------------------------------------------------
Plan hash value: 2949544139

--------------------------------------------------------------------------------------
| Id  | Operation                   | Name   | Rows  | Bytes | Cost (%CPU)| Time     |
--------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT            |        |     1 |    38 |     1   (0)| 00:00:01 |
|   1 |  TABLE ACCESS BY INDEX ROWID| EMP    |     1 |    38 |     1   (0)| 00:00:01 |
|*  2 |   INDEX UNIQUE SCAN         | PK_EMP |     1 |       |     0   (0)| 00:00:01 |
--------------------------------------------------------------------------------------

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

   2 - access("EMPNO"=7521)


统计信息
----------------------------------------------------------
          0  recursive calls
          0  db block gets
          2  consistent gets
          0  physical reads
          0  redo size
        902  bytes sent via SQL*Net to client
        508  bytes received via SQL*Net from client
          1  SQL*Net roundtrips to/from client
          0  sorts (memory)
          0  sorts (disk)
          1  rows processed

scott@GULL>

三、V$SQL_PLAN

直接取数据字典的源数据

scott@GULL> col id format 99;
scott@GULL> col parent_id format 99999;
scott@GULL> col operation format a25;
scott@GULL> col options format a20;
scott@GULL> select id,parent_id,operation,options from V$SQL_PLAN where sql_id='bjqjt2dfvya84';

 ID PARENT_ID OPERATION                 OPTIONS
--- --------- ------------------------- --------------------
  0           SELECT STATEMENT
  1         0 TABLE ACCESS              BY INDEX ROWID
  2         1 INDEX                     UNIQUE SCAN

四、?/rdbms/admin/awrsqrpt.sql

查看AWR中执行计划，调用这个脚本后，相关的直观展现

scott@GULL> @?/rdbms/admin/awrsqrpt.sql

Current Instance
~~~~~~~~~~~~~~~~

   DB Id    DB Name      Inst Num Instance
----------- ------------ -------- ------------
 3239200222 GULL                1 gullstby


Specify the Report Type
~~~~~~~~~~~~~~~~~~~~~~~
Would you like an HTML report, or a plain text report?
Enter 'html' for an HTML report, or 'text' for plain text
Defaults to 'html'
输入 report_type 的值:  html

Type Specified:  html


Instances in this Workload Repository schema
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

   DB Id     Inst Num DB Name      Instance     Host
------------ -------- ------------ ------------ ------------
* 3239200222        1 GULL         gullstby     gull02

Using 3239200222 for database Id
Using          1 for instance number


Specify the number of days of snapshots to choose from
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Entering the number of days (n) will result in the most recent
(n) days of snapshots being listed.  Pressing <return> without
specifying a number lists all completed snapshots.


输入 num_days 的值:  1

Listing the last day's Completed Snapshots

                                                        Snap
Instance     DB Name        Snap Id    Snap Started    Level
------------ ------------ --------- ------------------ -----
gullstby     GULL               368 01 6月  2016 10:08     1
                                369 01 6月  2016 10:12     1



Specify the Begin and End Snapshot Ids
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
输入 begin_snap 的值:  368
Begin Snapshot Id specified: 368

输入 end_snap 的值:  369
End   Snapshot Id specified: 369




Specify the SQL Id
~~~~~~~~~~~~~~~~~~
输入 sql_id 的值:  bjqjt2dfvya84
SQL ID specified:  bjqjt2dfvya84

Specify the Report Name
~~~~~~~~~~~~~~~~~~~~~~~
The default report file name is awrsqlrpt_1_368_369.html.  To use this name,
press <return> to continue, otherwise enter an alternative.

输入 report_name 的值:  /home/oracle/0601.html

五、工具类：toad（ctrl+e）、pl/SQL DEV(f5)

工具类查看执行计划，非常快捷、简单、能清楚知道每部步骤的优先级，但是他们实际调用的是EXPLAIN PLAN for，写入plan_TABLE，是优化器的预评估，不是正在SQL执行时的执行计划。简单分析是有用的，但是在你的应用程序中SQL很慢，常用的SQL用toad等很快，此时就不要在用工具快捷方式去查看执行计划，要去分析正在执行的执行计划，采用以上的内容方式。

toad(ctrl+e)

五、10046

10046这个事件是查看SQL具体的执行步骤，等待的是什么事件，实际内部调用的是哪些SQL。SQL语句执行很慢时，可以查看具体等待的是什么，导致执行这么慢。还有对我们了解create 、truncate具体在执行哪些语句有帮组。

SQL> conn /as sysdba
已连接。
SQL> ALTER SESSION SET EVENTS '10046 trace name context forever, level 28';

会话已更改。

SQL> select *　from scott.emp where empno=7521;

SQL> select c.value || '/' || d.instance_name || '_ora_' ||
  2            a.spid || '.trc' ||
  3             case when e.value is not null then '_'||e.value end trace
  4        from v$process a, v$session b, v$parameter c, v$instance d, v$parameter e
  5       where a.addr = b.paddr
  6         and b.sid = userenv('sid')
  7         and c.name = 'user_dump_dest'
  8         and e.name = 'tracefile_identifier';

TRACE
--------------------------------------------------------------------------------
/u01/app/oracle/diag/rdbms/orclstby/orcl/trace/orcl_ora_3288.trc 查看日志文件的内容
....
PARSING IN CURSOR #139774981787448 len=41 dep=0 uid=0 oct=3 lid=0 tim=1464851500943287 hv=3602254372 ad='d4180e00' sqlid='89mgdagbbc2j4'
select *　from scott.emp where empno=7521
END OF STMT
PARSE #139774981787448:c=60990,e=224928,p=20,cr=444,cu=0,mis=1,r=0,dep=0,og=1,plh=2949544139,tim=1464851500943287
EXEC #139774981787448:c=0,e=0,p=0,cr=0,cu=0,mis=0,r=0,dep=0,og=1,plh=2949544139,tim=1464851500943287
WAIT #139774981787448: nam='SQL*Net message to client' ela= 1 driver id=1650815232 #bytes=1 p3=0 obj#=5473 tim=1464851500943295
WAIT #139774981787448: nam='Disk file operations I/O' ela= 29 FileOperation=2 fileno=4 filetype=2 obj#=75336 tim=1464851500943586
WAIT #139774981787448: nam='db file sequential read' ela= 11120 file#=4 block#=155 blocks=1 obj#=75336 tim=1464851500954730
WAIT #139774981787448: nam='db file sequential read' ela= 428 file#=4 block#=151 blocks=1 obj#=75335 tim=1464851500955277
FETCH #139774981787448:c=0,e=12010,p=2,cr=2,cu=0,mis=0,r=1,dep=0,og=1,plh=2949544139,tim=1464851500955332
STAT #139774981787448 id=1 cnt=1 pid=0 pos=1 obj=75335 op='TABLE ACCESS BY INDEX ROWID EMP (cr=2 pr=2 pw=0 time=11994 us cost=1 size=38 card=1)'
STAT #139774981787448 id=2 cnt=1 pid=1 pos=1 obj=75336 op='INDEX UNIQUE SCAN PK_EMP (cr=1 pr=1 pw=0 time=11487 us cost=0 size=0 card=1)'
WAIT #139774981787448: nam='SQL*Net message from client' ela= 297 driver id=1650815232 #bytes=1 p3=0 obj#=75335 tim=1464851500955736
FETCH #139774981787448:c=0,e=2,p=0,cr=0,cu=0,mis=0,r=0,dep=0,og=0,plh=2949544139,tim=1464851500955773
WAIT #139774981787448: nam='SQL*Net message to client' ela= 1 driver id=1650815232 #bytes=1 p3=0 obj#=75335 tim=1464851500955791
采用tkprof格式化10046，看起来更加的清晰
[oracle@gull2 ~]$ tkprof /u01/app/oracle/diag/rdbms/orclstby/orcl/trace/orcl_ora_3288.trc /home/oracle/3288.trc
查看3288.trc
SQL ID: 89mgdagbbc2j4 Plan Hash: 2949544139

select *afrom scott.emp where empno=7521


call     count       cpu    elapsed       disk      query    current        rows
------- ------  -------- ---------- ---------- ---------- ----------  ----------
Parse        1      0.06       0.22          0        444          0           0
Execute      1      0.00       0.00          0          0          0           0
Fetch        2      0.00       0.01          2          2          0           1
------- ------  -------- ---------- ---------- ---------- ----------  ----------
total        4      0.06       0.23          2        446          0           1

Misses in library cache during parse: 1
Optimizer mode: ALL_ROWS
Parsing user id: SYS
Number of plan statistics captured: 1

Rows (1st) Rows (avg) Rows (max)  Row Source Operation
---------- ---------- ----------  ---------------------------------------------------
         1          1          1  TABLE ACCESS BY INDEX ROWID EMP (cr=2 pr=2 pw=0 time=11994 us cost=1 size=38 card=1)
         1          1          1   INDEX UNIQUE SCAN PK_EMP (cr=1 pr=1 pw=0 time=11487 us cost=0 size=0 card=1)(object id 75336)


Elapsed times include waiting on following events:
  Event waited on                             Times   Max. Wait  Total Waited
  ----------------------------------------   Waited  ----------  ------------
  SQL*Net break/reset to client                   2        0.00          0.00
  SQL*Net message to client                       3        0.00          0.00
  SQL*Net message from client                     2       11.43         11.43
  Disk file operations I/O                        1        0.00          0.00
  db file sequential read                         2        0.01          0.01

六、10053

10053这个事件是查看为什么SQL语句评估出发的执行计划是这样的，优化器如何评估出来这个执行计划的，记录优化器的计算值

SQL> conn /as sysdba
已连接。
SQL>  oradebug setmypid;
已处理的语句
SQL>  oradebug event 10053 trace name context forever ,level 1;
已处理的语句
SQL>  select *　from  scott.emp   where    empno=7521;

     EMPNO ENAME                          JOB                                MGR
---------- ------------------------------ --------------------------- ----------
HIREDATE              SAL       COMM     DEPTNO
-------------- ---------- ---------- ----------
      7521 WARD                           SALESMAN                          7698
22-2月 -81           1250        500         30


SQL> oradebug tracefile_name
/u01/app/oracle/diag/rdbms/orclstby/orcl/trace/orcl_ora_9109.trc
.......
Starting SQL statement dump

user_id=0 user_name=SYS module=sqlplus@gull2 (TNS V1-V3) action=
sql_id=b250dw0hyz0rs plan_hash_value=-1345423157 problem_type=3
----- Current SQL Statement for this session (sql_id=b250dw0hyz0rs) -----
 select *　from  scott.emp   where    empno=7521
sql_text_length=49
sql= select *　from  scott.emp   where    empno=7521
----- Explain Plan Dump -----
----- Plan Table -----

============
Plan Table
============
-----------------------------------------------+-----------------------------------+
| Id  | Operation                    | Name    | Rows  | Bytes | Cost  | Time      |
-----------------------------------------------+-----------------------------------+
| 0   | SELECT STATEMENT             |         |       |       |     1 |           |
| 1   |  TABLE ACCESS BY INDEX ROWID | EMP     |     1 |    38 |     1 |  00:00:01 |
| 2   |   INDEX UNIQUE SCAN          | PK_EMP  |     1 |       |     0 |           |
-----------------------------------------------+-----------------------------------+
Predicate Information:
----------------------
2 - access("EMPNO"=7521)

Content of other_xml column
===========================
  db_version     : 11.2.0.3
  parse_schema   : SYS
  plan_hash      : 2949544139
  plan_hash_2    : 1767686164
  Outline Data:
  /*+
    BEGIN_OUTLINE_DATA
      IGNORE_OPTIM_EMBEDDED_HINTS
      OPTIMIZER_FEATURES_ENABLE('11.2.0.3')
      DB_VERSION('11.2.0.3')
      ALL_ROWS
      OUTLINE_LEAF(@"SEL$1")
      INDEX_RS_ASC(@"SEL$1" "EMP"@"SEL$1" ("EMP"."EMPNO"))
    END_OUTLINE_DATA
  */

总结

1、查看真实的执行计划，使用DBMS_XPLAN.DISPLAY_CUROR这个过程，可以清晰的展示SHARED_POOL-》libarary中的执行计划，不需要你重新去运行SQL语句，根据不同的格式输出你需要的内容，可以查看出统计信息是否陈旧、谓词中的字段类型是否有隐式转化（导致索引不能使用）等

2、DBMS_XPLAN.DISPLAY_AWR，查看AWR中的执行计划，是否存在多个执行计划，代价比较高-》消耗性能厉害的，更加直观的可以调用?/rdbms/admin/awrsqrpt.sql

3、sql*plus autotrace 需要重新去运行一遍SQL语句，查看现在运行的这个语句的执行计划，无法查看到，你程序中运行的那条语句的执行计划

4、工具调用（如toad 、PL/SQL DEV），实际采用的EXPLAIN PLAN FOR... 保存到plan_TABLE，是优化器的预评估。

5、10046的事件使用的范围在调试一个语句执行很慢，想清楚具体等待的是什么，慢在哪个阶段，还可以查看一些DDL的语句，内部语句的构造的方式，但查看执行计划，10046不是特别的方便，需要重新执行SQL语句，到服务器端拿日志文件

6、10053的事件可以用来分析 SQL语句为什么会做这个执行计划（如没有走索引，而是走了全表扫描）

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原文地址：https://www.cnblogs.com/gull/p/5547905.html