oracle查看执行计划之DBMS_XPLAN
使用DBMS_XPLAN包中的方法是在oracle数据库中得到目标SQL的执行计划的另一种方法。针对不同的应用场景吗，你可以选择如下四种方法中的一种：
select * from table(dbms_xplan.display)
select * from table(dbms_xplan.display_cursor(null,null,'advenced'));
select * from table(dbms_xplan.display_cursor('sql_id/hash_value',child_cursor_number,'advanced'));
select * from table(dbms_xplan.display_awr('sql_id'));
方法1是执行select * from table(dbms_xplan.display)，这需要与explain plan命令配合使用，它用于查看使用explain plan命令后得到的执行计划。
方法2是执行select * from table(dbms_xplan.display_cursor(null,null,'advenced'));它用于查看刚刚执行过的sql的执行计划，这里针对dbms_xplan.display_cursor所传入的第一个和第二参数的值均为null，第三参数的值是“advanced”，第三个输入参数的值也可以是“all”，只不过用“advanced”后的显示结果会比用“all”的显示结果更详细些。
SQL> conn scott/scott;
Connected.
SQL> set linesize 800
SQL> set pagesize 900
SQL> col plan_table_output for a200
SQL> select empno,ename,dname from emp,dept where emp.deptno=dept.deptno;
EMPNO ENAME DNAME
---------- ---------- --------------
7782 CLARK ACCOUNTING
7839 KING ACCOUNTING14 rows selected.
SQL> select * from table(dbms_xplan.display_cursor(null,null,'advanced'));
PLAN_TABLE_OUTPUT
-------------------------------------------------------------------------------------------
SQL_ID 7ww0fhpbqqt0n, child number 0
-------------------------------------
select empno,ename,dname from emp,dept where emp.deptno=dept.deptno
Plan hash value: 844388907
----------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
----------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | | | 6 (100)| |
| 1 | MERGE JOIN | | 14 | 364 | 6 (17)| 00:00:01 |
| 2 | TABLE ACCESS BY INDEX ROWID| DEPT | 4 | 52 | 2 (0)| 00:00:01 |
| 3 | INDEX FULL SCAN | PK_DEPT | 4 | | 1 (0)| 00:00:01 |
|* 4 | SORT JOIN | | 14 | 182 | 4 (25)| 00:00:01 |
| 5 | TABLE ACCESS FULL | EMP | 14 | 182 | 3 (0)| 00:00:01 |
----------------------------------------------------------------------------------------
Query Block Name / Object Alias (identified by operation id):
-------------------------------------------------------------
1 - SEL$1
2 - SEL$1 / DEPT@SEL$1
3 - SEL$1 / DEPT@SEL$1
5 - SEL$1 / EMP@SEL$1
Outline Data
-------------
/*+
BEGIN_OUTLINE_DATA
IGNORE_OPTIM_EMBEDDED_HINTS
OPTIMIZER_FEATURES_ENABLE('11.2.0.4')
DB_VERSION('11.2.0.4')
ALL_ROWS
OUTLINE_LEAF(@"SEL$1")
INDEX(@"SEL$1" "DEPT"@"SEL$1" ("DEPT"."DEPTNO"))
FULL(@"SEL$1" "EMP"@"SEL$1")
LEADING(@"SEL$1" "DEPT"@"SEL$1" "EMP"@"SEL$1")
USE_MERGE(@"SEL$1" "EMP"@"SEL$1")
END_OUTLINE_DATA
*/
Predicate Information (identified by operation id):
---------------------------------------------------
4 - access("EMP"."DEPTNO"="DEPT"."DEPTNO")
filter("EMP"."DEPTNO"="DEPT"."DEPTNO")
Column Projection Information (identified by operation id):
-----------------------------------------------------------
1 - "DNAME"[VARCHAR2,14], "EMPNO"[NUMBER,22], "ENAME"[VARCHAR2,10]
2 - "DEPT"."DEPTNO"[NUMBER,22], "DNAME"[VARCHAR2,14]
3 - "DEPT".ROWID[ROWID,10], "DEPT"."DEPTNO"[NUMBER,22]
4 - (#keys=1) "EMP"."DEPTNO"[NUMBER,22], "EMPNO"[NUMBER,22],
"ENAME"[VARCHAR2,10]
5 - "EMPNO"[NUMBER,22], "ENAME"[VARCHAR2,10], "EMP"."DEPTNO"[NUMBER,22]
58 rows selected.
SQL> select * from table(dbms_xplan.display_cursor(null,null,'all'));
PLAN_TABLE_OUTPUT
-------------------------------------------------------------------------------------------
SQL_ID 7ww0fhpbqqt0n, child number 0
-------------------------------------
select empno,ename,dname from emp,dept where emp.deptno=dept.deptno
Plan hash value: 844388907
----------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
----------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | | | 6 (100)| |
| 1 | MERGE JOIN | | 14 | 364 | 6 (17)| 00:00:01 |
| 2 | TABLE ACCESS BY INDEX ROWID| DEPT | 4 | 52 | 2 (0)| 00:00:01 |
| 3 | INDEX FULL SCAN | PK_DEPT | 4 | | 1 (0)| 00:00:01 |
|* 4 | SORT JOIN | | 14 | 182 | 4 (25)| 00:00:01 |
| 5 | TABLE ACCESS FULL | EMP | 14 | 182 | 3 (0)| 00:00:01 |
----------------------------------------------------------------------------------------
Query Block Name / Object Alias (identified by operation id):
-------------------------------------------------------------
1 - SEL$1
2 - SEL$1 / DEPT@SEL$1
3 - SEL$1 / DEPT@SEL$1
5 - SEL$1 / EMP@SEL$1
Predicate Information (identified by operation id):
---------------------------------------------------
4 - access("EMP"."DEPTNO"="DEPT"."DEPTNO")
filter("EMP"."DEPTNO"="DEPT"."DEPTNO")
Column Projection Information (identified by operation id):
-----------------------------------------------------------
1 - "DNAME"[VARCHAR2,14], "EMPNO"[NUMBER,22], "ENAME"[VARCHAR2,10]
2 - "DEPT"."DEPTNO"[NUMBER,22], "DNAME"[VARCHAR2,14]
3 - "DEPT".ROWID[ROWID,10], "DEPT"."DEPTNO"[NUMBER,22]
4 - (#keys=1) "EMP"."DEPTNO"[NUMBER,22], "EMPNO"[NUMBER,22],
"ENAME"[VARCHAR2,10]
5 - "EMPNO"[NUMBER,22], "ENAME"[VARCHAR2,10], "EMP"."DEPTNO"[NUMBER,22]
41 rows selected.
当参数传入all，显示结果中了“Qutline Data”部分的内容：
方法3是执行 select * from table(dbms_xplan.display_cursor('sql_id/hash_value',child_cursor_number,'advanced'));它用于查看指定sql的执行计划。这里针对方法dbms_xplan.display_cursor所传人的第一个参数的值是指定sql的sql_id或者sql hash value,第二参数的值是要看执行计划所在的child cursor number，第三个参数是advcanced或者all
SQL> select sql_text,sql_id,hash_value,child_number from v$sql where sql_text like 'select empno,ename,dname%';
SQL_TEXT
select empno,ename,dname from emp,dept where emp.deptno=dept.deptno
SQL_ID HASH_VALUE CHILD_NUMBER
------------- ---------- ------------
7ww0fhpbqqt0n 1466655764 0
只要目标sql的执行计划所在的child cursor还没有被page out出shared pool，就可以使用方法3查看该sql的执行计划：
SQL> select * from table(dbms_xplan.display_cursor('2qm0f3qgsqqyc',0,'advanced'));
PLAN_TABLE_OUTPUT
-------------------------------------------------------------------------------------------
SQL_ID 2qm0f3qgsqqyc, child number 0
-------------------------------------
select empno,ename,dname from scott.emp,scott.dept where
scott.emp.deptno=scott.dept.deptno
Plan hash value: 844388907
----------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
----------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | | | 6 (100)| |
| 1 | MERGE JOIN | | 14 | 364 | 6 (17)| 00:00:01 |
| 2 | TABLE ACCESS BY INDEX ROWID| DEPT | 4 | 52 | 2 (0)| 00:00:01 |
| 3 | INDEX FULL SCAN | PK_DEPT | 4 | | 1 (0)| 00:00:01 |
|* 4 | SORT JOIN | | 14 | 182 | 4 (25)| 00:00:01 |
| 5 | TABLE ACCESS FULL | EMP | 14 | 182 | 3 (0)| 00:00:01 |
----------------------------------------------------------------------------------------
Query Block Name / Object Alias (identified by operation id):
-------------------------------------------------------------
1 - SEL$1
2 - SEL$1 / DEPT@SEL$1
3 - SEL$1 / DEPT@SEL$1
5 - SEL$1 / EMP@SEL$1
Outline Data
-------------
/*+
BEGIN_OUTLINE_DATA
IGNORE_OPTIM_EMBEDDED_HINTS
OPTIMIZER_FEATURES_ENABLE('11.2.0.4')
DB_VERSION('11.2.0.4')
ALL_ROWS
OUTLINE_LEAF(@"SEL$1")
INDEX(@"SEL$1" "DEPT"@"SEL$1" ("DEPT"."DEPTNO"))
FULL(@"SEL$1" "EMP"@"SEL$1")
LEADING(@"SEL$1" "DEPT"@"SEL$1" "EMP"@"SEL$1")
USE_MERGE(@"SEL$1" "EMP"@"SEL$1")
END_OUTLINE_DATA
*/
Predicate Information (identified by operation id):
---------------------------------------------------
4 - access("EMP"."DEPTNO"="DEPT"."DEPTNO")
filter("EMP"."DEPTNO"="DEPT"."DEPTNO")
Column Projection Information (identified by operation id):
-----------------------------------------------------------
1 - "DNAME"[VARCHAR2,14], "EMPNO"[NUMBER,22], "ENAME"[VARCHAR2,10]
2 - "DEPT"."DEPTNO"[NUMBER,22], "DNAME"[VARCHAR2,14]
3 - "DEPT".ROWID[ROWID,10], "DEPT"."DEPTNO"[NUMBER,22]
4 - (#keys=1) "EMP"."DEPTNO"[NUMBER,22], "EMPNO"[NUMBER,22],
"ENAME"[VARCHAR2,10]
5 - "EMPNO"[NUMBER,22], "ENAME"[VARCHAR2,10], "EMP"."DEPTNO"[NUMBER,22]
59 rows selected.
我们可以通过dbms_xplan.display_awr来得到该sql的所有历史执行计划：
SQL> set lines 100
SQL> select * from table(dbms_xplan.display_awr('cy097a90nu4fk'));
PLAN_TABLE_OUTPUT
SQL_ID cy097a90nu4fk
--------------------
Plan hash value: 1999179007
-------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
Inst |IN-OUT|
-------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | | | 11 (100)| |
| |
| 1 | HASH GROUP BY | | 1 | 101 | 11 (19)| 00:00:01 |
| |
| 2 | VIEW | | 1 | 101 | 10 (10)| 00:00:01 |
| |
| 3 | HASH GROUP BY | | 1 | 261 | 10 (10)| 00:00:01 |
| |
| 4 | FILTER | | | | | |
| |
| 5 | NESTED LOOPS | | | | | |
| |
| 6 | NESTED LOOPS | | 1 | 261 | 9 (0)| 00:00:01 |
| |
| 7 | REMOTE | | 1 | 176 | 5 (0)| 00:00:01 |
DBLK_~ | R->S |
| 8 | INDEX RANGE SCAN | PRODUCTSPEC_PK | 1 | | 1 (0)| 00:00:01 |
| |
| 9 | TABLE ACCESS BY INDEX ROWID| PRODUCTSPEC | 1 | 41 | 2 (0)| 00:00:01 |
| |
-------------------------------------------------------------------------------------------
Remote SQL Information (identified by operation id):
----------------------------------------------------
7 - SELECT "A1"."EVENTTIMEKEY","A1"."EVENTID","A1"."EVENTTIME","A1"."FOLLOTID","A1"."PRODUCTSPECI
D","A1"
."PROCESSFLOWID","A1"."OLDOPERATIONID","A1"."QUANTITY","A1"."EQUIPMENTID","A2"."PROCESSFLOWID
","A2"."REWORK
TYPE" FROM "LOTHISTORY" "A1","PROCESSFLOW" "A2" WHERE "A2"."REWORKTYPE"='Normal' AND
"A1"."PROCESSFLOWID"="A2"."PROCESSFLOWID" AND "A1"."EVENTID"='TrackIn' AND "A1"."OLDOPERATION
ID"='BFOP001'
AND (SUBSTR("A1"."FOLLOTID",1,1)='V' OR SUBSTR("A1"."FOLLOTID",1,1)='P') AND
"A1"."EVENTTIME">=TO_DATE('20140918080001','YYYY-MM-DD HH24:MI:SS') AND
"A1"."EVENTTIME"<=TO_DATE('20140919080000','YYYY-MM-DD HH24:MI:SS') (accessing 'DBLK_RPT_EOL_
PRD' )
55 rows selected.
不过此方法显示执行计划中看不到执行步骤对应的谓词条件。