读懂执行计划有什么用呢？
执行计划贯穿Oracle调优始终。
了解执行计划的真实执行过程，将有助于优化。
对亍Oracle的原理理解有一定帮助。
读懂执行计划，SQL调优的第一步。
什么是SQL Execution Plan执行计划？
SQL是声明型语言，她只说我要去哪里，但很少告诉你到底如何去？
SQL语句的执行最终会落实为Oracle执行步骤的组合 =>【SQL执行计划】
查看执行计划的方法
SQLPLUS AUTOTRACE
Explain Plan For SQL
SQL_TRACE
使用DBMS_XPLAN包
V$SQL和V$SQL_PLAN
Enterprise Manager
其他第三方工具
如何使用sqlplus autotrace.
SQL> set autotrace help
Usage: SET AUTOT[RACE] {OFF | ON | TRACE[ONLY]} [EXP[LAIN]] [STAT[ISTICS]]SQL> conn scott/tiger
Connected.
SQL> set autotrace on
SP2-0618: Cannot find the Session Identifier. Check PLUSTRACE role is enabled
SP2-0611: Error enabling STATISTICS report普通用户要使用这个功能，必须建立plustrace角色，并且赋给该用户。Oracle已经为我们提供了这个脚本。
SQL> conn / as sysdba
Connected.
SQL> @?/sqlplus/admin/plustrce.sql
SQL>
SQL> drop role plustrace;
drop role plustrace
*
ERROR at line 1:
ORA-01919: role 'PLUSTRACE' does not exist
SQL> create role plustrace;
Role created.
SQL>
SQL> grant select on v_$sesstat to plustrace;
Grant succeeded.
SQL> grant select on v_$statname to plustrace;
Grant succeeded.
SQL> grant select on v_$mystat to plustrace;
Grant succeeded.
SQL> grant plustrace to dba with admin option;
Grant succeeded.
SQL>
SQL> set echo off我们将plustrace角色赋予scott用户
SQL> grant plustrace to scott;
Grant succeeded.再次执行set autotrace
SQL> conn scott/tiger
Connected.
SQL> set autotrace on
SQL> select * from dept;
DEPTNO DNAME LOC
---------- -------------------- ---------------------------------------
10 ACCOUNTING NEW YORK
20 RESEARCH DALLAS
30 SALES CHICAGO
40 OPERATIONS BOSTON
Execution Plan
----------------------------------------------------------
Plan hash value: 3383998547
--------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
--------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 4 | 80 | 3 (0)| 00:00:01 |
| 1 | TABLE ACCESS FULL| DEPT | 4 | 80 | 3 (0)| 00:00:01 |
--------------------------------------------------------------------------
Statistics
----------------------------------------------------------
65 recursive calls
0 db block gets
66 consistent gets
6 physical reads
0 redo size
802 bytes sent via SQL*Net to client
523 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
6 sorts (memory)
0 sorts (disk)
4 rows processed如上，结果分三部分
查询结果集、执行计划、统计信息。
set autotrace on 后面可以跟三个类型的参数：
traceonly -- 表示不执行真正的查询，只是把执行计划与统计信息打印出来。
explain -- 只打印查询结果和执行计划。
stat -- 只打印查询结果和统计信息。
执行计划解析：
Id 表示每一步的编号，并不表示执行的序列号。
Operation 表示执行步骤的名称
Name 表示对象的名称
Rows 表示查询结果返回的行数
Bytes 表示返回结果集的大小
Cost 表示执行计划的成本，用来衡量执行sql的速度，你可以把它想象成一个虚拟的时间单位。它的 计算方式比较复杂，依赖于系统的cpu、io等因素。
Time 语句执行的耗时
统计信息解析：
recursive calls ：递归调用次数，为你执行的sql所执行的sql语句的条目
db block gets：用当前读方式从buffer cache中读取块数
consistent reads：用一致性读的方式从buffer cache中读取的块数。
physical reads：物理读，从磁盘上读取了多少个块。
redo size： sql产生的redo大小
bytes sent via SQL*Net to client：从服务器发往客户端的字节总数
bytes received via SQL*Net from client：客户机接受的字节数
SQL*Net roundtrips to/from client：从客户机到服务器之间发生SQL*Net的次数
sorts (memory)：在内存中排序
sorts (disk)：磁盘中排序
rows processed：影响数据的行数
下面我们看一个比较复杂的sql执行计划
SQL> set pagesize 200
SQL> set linesize 200
SQL> set autot on
SQL> select * from tab where rownum<=1;
TNAME TABTYPE CLUSTERID
------------------------------------------------------------------------------------------ --------------------- ----------
ACCESS$ TABLE
Execution Plan
----------------------------------------------------------
Plan hash value: 3245953645
-----------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
-----------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 106 | 4 (0)| 00:00:01 |
|* 1 | COUNT STOPKEY | | | | | |
|* 2 | FILTER | | | | | |
| 3 | NESTED LOOPS OUTER | | 1 | 106 | 4 (0)| 00:00:01 |
| 4 | NESTED LOOPS | | 1 | 99 | 3 (0)| 00:00:01 |
|* 5 | INDEX RANGE SCAN | I_OBJ5 | 1 | 77 | 2 (0)| 00:00:01 |
|* 6 | INDEX RANGE SCAN | I_USER2 | 1 | 22 | 1 (0)| 00:00:01 |
| 7 | TABLE ACCESS CLUSTER| TAB$ | 1 | 7 | 1 (0)| 00:00:01 |
|* 8 | INDEX UNIQUE SCAN | I_OBJ# | 1 | | 0 (0)| 00:00:01 |
| 9 | NESTED LOOPS | | 1 | 29 | 2 (0)| 00:00:01 |
|* 10 | INDEX SKIP SCAN | I_USER2 | 1 | 20 | 1 (0)| 00:00:01 |
|* 11 | INDEX RANGE SCAN | I_OBJ4 | 1 | 9 | 1 (0)| 00:00:01 |
-----------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - filter(ROWNUM<=1)
2 - filter("O"."TYPE#"<>4 AND "O"."TYPE#"<>5 AND "O"."TYPE#"<>7 AND
"O"."TYPE#"<>8 AND "O"."TYPE#"<>9 AND "O"."TYPE#"<>10 AND "O"."TYPE#"<>11
AND "O"."TYPE#"<>12 AND "O"."TYPE#"<>13 AND "O"."TYPE#"<>14 AND
"O"."TYPE#"<>22 AND "O"."TYPE#"<>87 AND "O"."TYPE#"<>88 OR
BITAND("U"."SPARE1",16)=0 OR ("O"."TYPE#"=4 OR "O"."TYPE#"=5) AND
(SYS_CONTEXT('userenv','current_edition_name')='ORA$BASE' AND
"U"."TYPE#"<>2 OR "U"."TYPE#"=2 AND "U"."SPARE2"=TO_NUMBER(SYS_CONTEXT('use
renv','current_edition_id')) OR EXISTS (SELECT 0 FROM SYS."USER$"
"U2",SYS."OBJ$" "O2" WHERE "O2"."OWNER#"="U2"."USER#" AND "O2"."TYPE#"=88
AND "O2"."DATAOBJ#"=:B1 AND "U2"."TYPE#"=2 AND
"U2"."SPARE2"=TO_NUMBER(SYS_CONTEXT('userenv','current_edition_id')))))
5 - access("O"."SPARE3"=USERENV('SCHEMAID') AND "O"."TYPE#">=2 AND
"O"."LINKNAME" IS NULL AND "O"."TYPE#"<=5)
filter("O"."TYPE#"<=5 AND "O"."TYPE#">=2 AND "O"."LINKNAME" IS NULL)
6 - access("O"."OWNER#"="U"."USER#")
8 - access("O"."OBJ#"="T"."OBJ#"(+))
10 - access("U2"."TYPE#"=2 AND "U2"."SPARE2"=TO_NUMBER(SYS_CONTEXT('usere
nv','current_edition_id')))
filter("U2"."TYPE#"=2 AND "U2"."SPARE2"=TO_NUMBER(SYS_CONTEXT('usere
nv','current_edition_id')))
11 - access("O2"."DATAOBJ#"=:B1 AND "O2"."TYPE#"=88 AND
"O2"."OWNER#"="U2"."USER#")
Statistics
----------------------------------------------------------
0 recursive calls
0 db block gets
153 consistent gets
0 physical reads
0 redo size
675 bytes sent via SQL*Net to client
523 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
1 rows processed这个执行计划，不单复杂，而且多出了一块
Predicate Information (identified by operation id):
前面的序号，和执行计划中的id对应。filter表示表过滤条件，access表示索引过滤。
执行计划到底该怎么解读呢？
我们先把执行计划以‘树’的形式画出来。
从0开始，用缩进表示父子关系。
0的儿子为1
1的儿子为2
2的儿子为3和9
3的儿子为4和7
4的儿子为5,6
7的儿子为8
9的儿子为10,11
如下图：
正确的计划树形图解析顺序
树形图的解析过程：
1.从顶部开始。
2.在树中向左下移，直至到达左节点(没有子节点的节点)。首先执行此节点。
3.查看此行源的同级行源。接下来执行这些行源。
4.执行子行源后，接着执行父行源。
5.在树中不断上移，直至用完所有行源为止。
上图的执行顺序：
1.左下移动5节点没有子节点，优先执行5
2.遍历5的同级别行源6，执行6
3.执行4
4.遍历同级节点7，执行其子节点8
5.执行3
6.遍历同级节点，执行其最左下节点，执行10
7.执行11
8.执行9
9.执行2
10.执行1
11.执行0
二、Explain Plan For SQL
SQL> explain plan for select * from emp;
Explained.显示执行计划
SQL> @?/rdbms/admin/utlxpls
PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Plan hash value: 3956160932
--------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
--------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 14 | 532 | 3 (0)| 00:00:01 |
| 1 | TABLE ACCESS FULL| EMP | 14 | 532 | 3 (0)| 00:00:01 |
--------------------------------------------------------------------------
8 rows selected.这种方法并没有真正的执行sql语句，查看执行计划也比较麻烦，基本上不使用。
三、SQL_TRACE
SQL_TRACE是Oracle的一个非常强大的工具。打开SQL_TRACE就可以逐步捕获任何一个会话的数据库活动，或者捕获整个数据库的活动，并将数据库活动记录成跟踪文件。每次使用完之后需要关闭跟踪,否则会降低系统的性能。
跟踪整个数据库实例。
只需要简单的修改参数文件(pfile/spfile)参数 SQL_TRACE = TRUE ，在全局启用SQL_TRACE会导致所有进程的活动被跟踪，包括后台进程及所有用户进程,这样也会数据库导致性能下降比较明显。
会话级跟踪。
SQL_TRACE的通常使用方式是仅跟踪一个会话。被跟踪的会话可以是您自己的，也可以是其它用户的会话。如果是自己的会话，只需要在SQL*PLUS中运行一下命令即可：
SQL> alter session set sql_trace = true; 类似的如果取消对会话的跟踪，运行一下命令：
SQL> alter session set sql_trace = false; 如果需要跟踪一个特定的会话，首先需要获取会话的SID和Serial#，这些信息可以在视图V$SESSION中获得，一旦知道了这两个参数，就可以运行一下命令：
SQL> execute SYS.dbms_system.set_sql_trace_in_session(13,9,true);同样也可以使用这个过程关闭会话跟踪：
SQL> execute SYS.dbms_system.set_sql_trace_in_session(13,9,false);跟踪文件的位置：
一旦为会话激活了SQL_TRACE，ORACLE就会在udump管理区创建跟踪文件，文件的目标位置由参数user_dump_dest来确定。每个操作都不会覆盖原来的文件，新的跟踪记录将会被追加到文件末尾。通常情况下，可以根据文件的修改时间判断目录下哪个文件是最新的文件。
SQL> show parameter user_dump_dest
NAME TYPE VALUE
------------------------------------ --------------------------------- ------------------------------
user_dump_dest string /u01/app/oracle/diag/rdbms/11g
dg1/dgtst/trace
SQL>也可以通过以下SQL来确定文件名：
SQL> SELECT d.VALUE
|| '/'
|| LOWER (RTRIM (i.instance, CHR (0)))
|| '_ora_'
|| p.spid
|| '.trc'
trace_file_name
FROM (SELECT p.spid
FROM v$mystat m, v$session s, v$process p
WHERE m.statistic# = 1 AND s.sid = m.sid AND p.addr = s.paddr) p,
(SELECT t.instance
FROM v$thread t, v$parameter v
WHERE v.name = 'thread'
AND (v.VALUE = 0 OR t.thread# = TO_NUMBER (v.VALUE))) i,
(SELECT VALUE
FROM v$parameter
WHERE name = 'user_dump_dest') d;
TRACE_FILE_NAME
-----------------------------------------------------------------------------------------
/u01/app/oracle/diag/rdbms/11gdg1/dgtst/trace/dgtst_ora_11347.trc计时信息：
为了最大限度的利用跟踪文件，应该打开计时标志,通过参数TIMED_STATISTICTS=TRUE进行设置，这样可以对每个SQL语句的执行时间等进行记录，这个功能对系统性能的负担很小。
打开会话的计时信息:
SQL> alter session set timed_statistics = true ;打开数据库系统的计时信息
SQL> alter system set timed_statistics = true ;我们来做一个实验：
SQL> alter session set sql_trace=true;
ERROR:
ORA-01031: insufficient privilegesSQL> conn / as sysdba
Connected.
SQL> grant alter session to scott;
Grant succeeded.执行一个查询
SQL> alter session set sql_trace=true;
Session altered.
SQL> select * from emp,dept where emp.deptno=dept.deptno;获取trace_file_name
TRACE_FILE_NAME
----------------------------------------------------------------------------------------------------
/u01/app/oracle/diag/rdbms/11gdg1/dgtst/trace/dgtst_ora_11450.trc查看trace file
11gdg1-> cat /u01/app/oracle/diag/rdbms/11gdg1/dgtst/trace/dgtst_ora_11450.trc
Trace file /u01/app/oracle/diag/rdbms/11gdg1/dgtst/trace/dgtst_ora_11450.trc
Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
ORACLE_HOME = /u01/app/oracle/product/11.2.0/db_1
System name: Linux
Node name: 11gdg1.localdomain.com
Release: 2.6.39-400.17.1.el6uek.x86_64
Version: #1 SMP Fri Feb 22 18:16:18 PST 2013
Machine: x86_64
VM name: VMWare Version: 6
Instance name: dgtst
Redo thread mounted by this instance: 1
Oracle process number: 23
Unix process pid: 11450, p_w_picpath: [email protected] (TNS V1-V3)
*** 2015-07-13 09:38:29.695
*** SESSION ID:(42.57) 2015-07-13 09:38:29.695
*** CLIENT ID:() 2015-07-13 09:38:29.695
*** SERVICE NAME:(SYS$USERS) 2015-07-13 09:38:29.695
*** MODULE NAME:(SQL*Plus) 2015-07-13 09:38:29.695
*** ACTION NAME:() 2015-07-13 09:38:29.695
=====================
PARSING IN CURSOR #139672104506696 len=32 dep=0 uid=83 oct=42 lid=83 tim=1436751509693664 hv=1569151342 ad='7f07f227fe10' sqlid='4tk6t8tfsfqbf'
alter session set sql_trace=true
END OF STMT
EXEC #139672104506696:c=0,e=601,p=0,cr=0,cu=0,mis=1,r=0,dep=0,og=1,plh=0,tim=1436751509693625
*** 2015-07-13 09:38:47.624
CLOSE #139672104506696:c=0,e=17,dep=0,type=0,tim=1436751527624224
=====================
PARSING IN CURSOR #139672104506696 len=51 dep=0 uid=83 oct=3 lid=83 tim=1436751527625170 hv=4289413451 ad='8bd40480' sqlid='arvwqrbzuqhab'
select * from emp,dept where emp.deptno=dept.deptno
END OF STMT
PARSE #139672104506696:c=0,e=814,p=0,cr=0,cu=0,mis=0,r=0,dep=0,og=1,plh=844388907,tim=1436751527625164
EXEC #139672104506696:c=0,e=315,p=0,cr=0,cu=0,mis=0,r=0,dep=0,og=1,plh=844388907,tim=1436751527625549
FETCH #139672104506696:c=1000,e=1189,p=0,cr=8,cu=0,mis=0,r=1,dep=0,og=1,plh=844388907,tim=1436751527641018
FETCH #139672104506696:c=0,e=52,p=0,cr=2,cu=0,mis=0,r=13,dep=0,og=1,plh=844388907,tim=1436751527641868
STAT #139672104506696 id=1 cnt=14 pid=0 pos=1 obj=0 op='MERGE JOIN (cr=10 pr=0 pw=0 time=1393 us cost=6 size=812 card=14)'
STAT #139672104506696 id=2 cnt=4 pid=1 pos=1 obj=75333 op='TABLE ACCESS BY INDEX ROWID DEPT (cr=4 pr=0 pw=0 time=605 us cost=2 size=80 card=4)'
STAT #139672104506696 id=3 cnt=4 pid=2 pos=1 obj=75334 op='INDEX FULL SCAN PK_DEPT (cr=2 pr=0 pw=0 time=286 us cost=1 size=0 card=4)'
STAT #139672104506696 id=4 cnt=14 pid=1 pos=2 obj=0 op='SORT JOIN (cr=6 pr=0 pw=0 time=818 us cost=4 size=532 card=14)'
STAT #139672104506696 id=5 cnt=14 pid=4 pos=1 obj=75335 op='TABLE ACCESS FULL EMP (cr=6 pr=0 pw=0 time=766 us cost=3 size=532 card=14)'如果你直接用cat命令查看上面的文件的话，根本看不懂。Oracle提供了一个工具TKPROF
11gdg1-> tkprof /u01/app/oracle/diag/rdbms/11gdg1/dgtst/trace/dgtst_ora_11450.trc trace.sql TKPROF: Release 11.2.0.3.0 - Development on Mon Jul 13 09:41:05 2015 Copyright (c) 1982, 2011, Oracle and/or its affiliates. All rights reserved.
11gdg1-> cat trace.sql TKPROF: Release 11.2.0.3.0 - Development on Mon Jul 13 09:41:05 2015 Copyright (c) 1982, 2011, Oracle and/or its affiliates. All rights reserved. Trace file: /u01/app/oracle/diag/rdbms/11gdg1/dgtst/trace/dgtst_ora_11450.trc Sort options: default ******************************************************************************** count = number of times OCI procedure was executed cpu = cpu time in seconds executing elapsed = elapsed time in seconds executing disk = number of physical reads of buffers from disk query = number of buffers gotten for consistent read current = number of buffers gotten in current mode (usually for update) rows = number of rows processed by the fetch or execute call ******************************************************************************** SQL ID: 4tk6t8tfsfqbf Plan Hash: 0 alter session set sql_trace=true call count cpu elapsed disk query current rows ------- ------ -------- ---------- ---------- ---------- ---------- ---------- Parse 0 0.00 0.00 0 0 0 0 Execute 1 0.00 0.00 0 0 0 0 Fetch 0 0.00 0.00 0 0 0 0 ------- ------ -------- ---------- ---------- ---------- ---------- ---------- total 1 0.00 0.00 0 0 0 0 Misses in library cache during parse: 0 Misses in library cache during execute: 1 Optimizer mode: ALL_ROWS Parsing user id: 83 ******************************************************************************** SQL ID: arvwqrbzuqhab Plan Hash: 844388907 select * from emp,dept where emp.deptno=dept.deptno call count cpu elapsed disk query current rows ------- ------ -------- ---------- ---------- ---------- ---------- ---------- Parse 1 0.00 0.00 0 0 0 0 Execute 1 0.00 0.00 0 0 0 0 Fetch 2 0.00 0.00 0 10 0 14 ------- ------ -------- ---------- ---------- ---------- ---------- ---------- total 4 0.00 0.00 0 10 0 14 Misses in library cache during parse: 0 Optimizer mode: ALL_ROWS Parsing user id: 83 Number of plan statistics captured: 1 Rows (1st) Rows (avg) Rows (max) Row Source Operation ---------- ---------- ---------- --------------------------------------------------- 14 14 14 MERGE JOIN (cr=10 pr=0 pw=0 time=1393 us cost=6 size=812 card=14) 4 4 4 TABLE ACCESS BY INDEX ROWID DEPT (cr=4 pr=0 pw=0 time=605 us cost=2 size=80 card=4) 4 4 4 INDEX FULL SCAN PK_DEPT (cr=2 pr=0 pw=0 time=286 us cost=1 size=0 card=4)(object id 75334) 14 14 14 SORT JOIN (cr=6 pr=0 pw=0 time=818 us cost=4 size=532 card=14) 14 14 14 TABLE ACCESS FULL EMP (cr=6 pr=0 pw=0 time=766 us cost=3 size=532 card=14) ******************************************************************************** OVERALL TOTALS FOR ALL NON-RECURSIVE STATEMENTS call count cpu elapsed disk query current rows ------- ------ -------- ---------- ---------- ---------- ---------- ---------- Parse 1 0.00 0.00 0 0 0 0 Execute 2 0.00 0.00 0 0 0 0 Fetch 2 0.00 0.00 0 10 0 14 ------- ------ -------- ---------- ---------- ---------- ---------- ---------- total 5 0.00 0.00 0 10 0 14 Misses in library cache during parse: 0 Misses in library cache during execute: 1 OVERALL TOTALS FOR ALL RECURSIVE STATEMENTS call count cpu elapsed disk query current rows ------- ------ -------- ---------- ---------- ---------- ---------- ---------- Parse 0 0.00 0.00 0 0 0 0 Execute 0 0.00 0.00 0 0 0 0 Fetch 0 0.00 0.00 0 0 0 0 ------- ------ -------- ---------- ---------- ---------- ---------- ---------- total 0 0.00 0.00 0 0 0 0 Misses in library cache during parse: 0 2 user SQL statements in session. 0 internal SQL statements in session. 2 SQL statements in session. ******************************************************************************** Trace file: /u01/app/oracle/diag/rdbms/11gdg1/dgtst/trace/dgtst_ora_11450.trc Trace file compatibility: 11.1.0.7 Sort options: default 1 session in tracefile. 2 user SQL statements in trace file. 0 internal SQL statements in trace file. 2 SQL statements in trace file. 2 unique SQL statements in trace file. 44 lines in trace file. 17 elapsed seconds in trace file.
四、使用DBMS_XPLAY
DBMS_XPLAN提供了5个函数
DISPLAY - 格式化和显示plan table中的内容。
DISPLAY_AWR - 格式化和显示存储在AWR中的sql语句的执行计划。
DISPLAY_CURSOR - 格式化和显示任意shared pool中加载的sql语句的执行计划。
DISPLAY_SQL_PLAN_BASELINE - 显示被SQL handle标识的SQL语句的一个或者多个执行计划。
DISPLAY_SQLSET - 格式化和显示存储在SQL tuning set中的sql语句的执行计划
1.DISPLAY
SQL> EXPLAIN PLAN FOR
SELECT * FROM emp e, dept d
WHERE e.deptno = d.deptno
AND e.ename='benoit';
Explained.
SQL> SET LINESIZE 130
SQL> SET PAGESIZE 0
SQL> SELECT * FROM table(DBMS_XPLAN.DISPLAY);
Plan hash value: 3625962092
----------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
----------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 58 | 4 (0)| 00:00:01 |
| 1 | NESTED LOOPS | | | | | |
| 2 | NESTED LOOPS | | 1 | 58 | 4 (0)| 00:00:01 |
|* 3 | TABLE ACCESS FULL | EMP | 1 | 38 | 3 (0)| 00:00:01 |
|* 4 | INDEX UNIQUE SCAN | PK_DEPT | 1 | | 0 (0)| 00:00:01 |
| 5 | TABLE ACCESS BY INDEX ROWID| DEPT | 1 | 20 | 1 (0)| 00:00:01 |
----------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
3 - filter("E"."ENAME"='benoit')
4 - access("E"."DEPTNO"="D"."DEPTNO")
18 rows selected.2. DISPLAY_AWR
SQL> SELECT SQL_ID FROM DBA_HIST_SQLTEXT WHERE ROWNUM<=1;
424h0nf7bhqzd
SQL> SELECT * FROM TABLE(DBMS_XPLAN.DISPLAY_AWR('424h0nf7bhqzd'));查看历史查询中包含TOTO的语句的执行计划
SELECT tf.*
FROM DBA_HIST_SQLTEXT ht,
TABLE (DBMS_XPLAN.DISPLAY_AWR (ht.sql_id,
NULL,
NULL,
'ALL')) tf
WHERE ht.sql_text LIKE '%TOTO%';3.DISPLAY_CURSOR
SQL> CONN SCOTT/tiger
Connected.
SQL> select * from emp where ename='KING';
EMPNO ENAME JOB MGR
---------- ------------------------------ --------------------------- ----------
HIREDATE SAL COMM DEPTNO
------------------- ---------- ---------- ----------
7839 KING PRESIDENT
1981/11/17 00:00:00 5000 10
SQL> set pagesize 200
SQL> select * from table(dbms_xplan.display_cursor);
PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
SQL_ID 7y29yzz506y9t, child number 0
-------------------------------------
select * from emp where ename='KING'
Plan hash value: 3956160932
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| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
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| 0 | SELECT STATEMENT | | | | 3 (100)| |
|* 1 | TABLE ACCESS FULL| EMP | 1 | 38 | 3 (0)| 00:00:01 |
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Predicate Information (identified by operation id):
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1 - filter("ENAME"='KING')
18 rows selected.DISPLAY_CURSOR还有很多丰富的用法，我们看看官方文档是怎么描述的。
查看一个具体sql_id的执行计划
SQL> SELECT SQL_ID FROM V$SQLAREA WHERE ROWNUM<=1;
SQL_ID
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4dy1xm4nxc0gf
SQL> select * from table(dbms_xplan.display_cursor('4dy1xm4nxc0gf',NULL,'ALL ALLSTATS'));4.DISPLAY_SQL_PLAN_BASELINE
SET LINESIZE 150
SET PAGESIZE 2000
SELECT t.*
FROM (SELECT DISTINCT sql_handle
FROM dba_sql_plan_baselines
WHERE sql_text LIKE '%DEPT%') pb,
TABLE (
DBMS_XPLAN.DISPLAY_SQL_PLAN_BASELINE (pb.sql_handle, NULL, 'BASIC')) t;