3.解释执行计划的方法
2013-08-06
－－－－－－－－－－－－－－解释执行计划的方法－－－－－－－－－－－－－－－－－－－－－－－－－－－－
用autotrace前提：
SQL> @/u01/oracle/product/10.2.0/db_1/sqlplus/admin/plustrce.sql --sys用户下执行
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> 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> set echo off
SQL> grant plustrace to scott; －－将权限授予SCOTT可以用autotrace
Grant succeeded.
-------------------------------------------------------------
1、autotrace工具详解
SQL> set autotrace off ――默认情况下是关闭的
SQL> set autotrace on exp －－显示查询结果、执行计划
SQL> select * from t where rownum=1;
OWNER OBJECT_TYPE
------------------------------ -------------------
PUBLIC SYNONYM
Execution Plan
----------------------------------------------------------
Plan hash value: 508354683
---------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
---------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 28 | 2 (0)| 00:00:01 |
|* 1 | COUNT STOPKEY | | | | | |
| 2 | TABLE ACCESS FULL| T | 45659 | 1248K| 2 (0)| 00:00:01 |
---------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - filter(ROWNUM=1)
Note
-----
- dynamic sampling used for this statement
SQL> set autotrace on --显示查询结果、执行计划、执行的物理统计信息
SQL> select * from t where rownum=1;
OBJECT_NAME OBJECT_TYPE
------------------------------ -------------------
DUAL TABLE
Execution Plan
----------------------------------------------------------
Plan hash value: 508354683
---------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
---------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 28 | 2 (0)| 00:00:01 |
|* 1 | COUNT STOPKEY | | | | | |
| 2 | TABLE ACCESS FULL| T | 43751 | 1196K| 2 (0)| 00:00:01 |
---------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - filter(ROWNUM=1)
Note
-----
- dynamic sampling used for this statement
Statistics
----------------------------------------------------------
71 recursive calls
0 db block gets
146 consistent gets
155 physical reads
0 redo size
483 bytes sent via SQL*Net to client
400 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
1 rows processed
SQL> set autotrace on stat －－显示查询结果、执行的物理统计信息
SQL> select * from t where rownum=1;
OBJECT_NAME OBJECT_TYPE
------------------------------ -------------------
DUAL TABLE
Statistics
----------------------------------------------------------
0 recursive calls
0 db block gets
4 consistent gets
0 physical reads
0 redo size
483 bytes sent via SQL*Net to client
400 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
1 rows processed
SQL> set autotrace trace exp －－显示执行计划
SQL> select * from t where rownum=1;
Execution Plan
----------------------------------------------------------
Plan hash value: 508354683
---------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
---------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 28 | 2 (0)| 00:00:01 |
|* 1 | COUNT STOPKEY | | | | | |
| 2 | TABLE ACCESS FULL| T | 43751 | 1196K| 2 (0)| 00:00:01 |
---------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - filter(ROWNUM=1)
Note
-----
- dynamic sampling used for this statement
SQL> set autotrace trace exp stat －－显示执行计划和物理统计信息
SQL> select * from t where rownum=1;
Execution Plan
----------------------------------------------------------
Plan hash value: 508354683
---------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
---------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 28 | 2 (0)| 00:00:01 |
|* 1 | COUNT STOPKEY | | | | | |
| 2 | TABLE ACCESS FULL| T | 43751 | 1196K| 2 (0)| 00:00:01 |
---------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - filter(ROWNUM=1)
Note
-----
- dynamic sampling used for this statement
Statistics
----------------------------------------------------------
0 recursive calls
0 db block gets
4 consistent gets
0 physical reads
0 redo size
483 bytes sent via SQL*Net to client
400 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
1 rows processed
SQL> set autotrace trace stat －－显示物理统计信息
SQL> select * from t where rownum=1;
Statistics
----------------------------------------------------------
0 recursive calls
0 db block gets
4 consistent gets
0 physical reads
0 redo size
483 bytes sent via SQL*Net to client
400 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
1 rows processed
---------------------------------------------------------------
总结：
set autotrace on ＝ set autotrace on exp stat
set autotrace on exp stat
on exp
on stat
trace ＝ trace exp stat
trace exp stat
trace exp
trace stat
只要有on，一定会显示数据，只要有trace，就不显示数据。
--------------------------------------------------------------------
2、dbms_xplan --通过内部的包，仅仅显示执行计划
解释执行计划
SQL> explain plan for select * from t where rownum=1;
Explained.
查看执行计划
SQL> select * from table(dbms_xplan.display);
PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
Plan hash value: 508354683
---------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
---------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 28 | 2 (0)| 00:00:01 |
|* 1 | COUNT STOPKEY | | | | | |
| 2 | TABLE ACCESS FULL| T | 43751 | 1196K| 2 (0)| 00:00:01 |
---------------------------------------------------------------------------
Predicate Information (identified by operation id):
PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
1 - filter(ROWNUM=1)
Note
-----
- dynamic sampling used for this statement
18 rows selected.