DBMS_XPLAN.DISPLAY

之前有用户在AWR中定位到问题SQL语句后想要了解该SQL statement的具体执行计划，于是就用AWR报告中得到的SQL ID去V$SQL等几个动态性能视图中查询，但发现V$SQL或V$SQL_PLAN视图都已经找不到对应SQL ID的记录，一般来说这些语句已经从shared pool共享池中被替换出去了。

这个时候我们可以尝试使用DBMS_XPLAN.DISPLAY_AWR存储过程来将Oracle Automatic Workload Repository自动负载仓库中记录的SQL语句相关信息抽取出来，如:

SQL> set linesize 200 pagesize 2000;

SQL> select * from global_name;

GLOBAL_NAME
--------------------------------------------------------------------------------
askmac.cn

SQL> select /* extract_me */ count(*) from maclean;

  COUNT(*)
----------
      9564

SQL> select sql_id from v$sql where sql_text like '%extract_me%' and sql_text not like '%like%';

SQL_ID
-------------
8vff23q8qp9fj

SQL> exec dbms_workload_repository.create_snapshot;
PL/SQL procedure successfully completed.

QL> select * from table(dbms_xplan.display_cursor('8vff23q8qp9fj',0));

PLAN_TABLE_OUTPUT
-------------------------------------
SQL_ID  8vff23q8qp9fj, child number 0
-------------------------------------
select /* extract_me */ count(*) from maclean

Plan hash value: 1679547536

----------------------------------------------------------------------
| Id  | Operation          | Name    | Rows  | Cost (%CPU)| Time     |
----------------------------------------------------------------------
|   0 | SELECT STATEMENT   |         |       |    34 (100)|          |
|   1 |  SORT AGGREGATE    |         |     1 |            |          |
|   2 |   TABLE ACCESS FULL| MACLEAN | 10438 |    34   (0)| 00:00:01 |
----------------------------------------------------------------------

Note
-----
   - dynamic sampling used for this statement

18 rows selected.

/* 冲刷共享池后v$SQL/V$SQL_PLAN等动态视图内的记录会消失,
     需要注意的是如果在AWR快照自动生成之前冲刷了共享池，那么可能丢失SQL的执行统计信息
 */

SQL> alter system flush shared_pool;
System altered.

SQL> select * from table(dbms_xplan.display_cursor('8vff23q8qp9fj',0));

PLAN_TABLE_OUTPUT
---------------------------------------------------------------------
SQL_ID: 8vff23q8qp9fj, child number: 0 cannot be found

/* 此时就可以利用dbms_xplan.display_awr存储过程来抓取该SQL_ID对应的执行计划 */

SQL>  select * from table(dbms_xplan.display_awr('8vff23q8qp9fj'));

PLAN_TABLE_OUTPUT
--------------------------------------------------
SQL_ID 8vff23q8qp9fj
--------------------
select /* extract_me */ count(*) from maclean

Plan hash value: 1679547536

----------------------------------------------------------------------
| Id  | Operation          | Name    | Rows  | Cost (%CPU)| Time     |
----------------------------------------------------------------------
|   0 | SELECT STATEMENT   |         |       |    34 (100)|          |
|   1 |  SORT AGGREGATE    |         |     1 |            |          |
|   2 |   TABLE ACCESS FULL| MACLEAN | 10438 |    34   (0)| 00:00:01 |
----------------------------------------------------------------------

Note
-----
   - dynamic sampling used for this statement

18 rows selected.

/* 这里可以代入'all'选项获取更细致的计划信息 */

SQL> select * from table(dbms_xplan.display_awr('8vff23q8qp9fj',null,null,'all'));

PLAN_TABLE_OUTPUT
----------------------------------------------------------------------------
SQL_ID 8vff23q8qp9fj
--------------------
select /* extract_me */ count(*) from maclean

Plan hash value: 1679547536

----------------------------------------------------------------------
| Id  | Operation          | Name    | Rows  | Cost (%CPU)| Time     |
----------------------------------------------------------------------
|   0 | SELECT STATEMENT   |         |       |    34 (100)|          |
|   1 |  SORT AGGREGATE    |         |     1 |            |          |
|   2 |   TABLE ACCESS FULL| MACLEAN | 10438 |    34   (0)| 00:00:01 |
----------------------------------------------------------------------

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

   1 - SEL$1
   2 - SEL$1 / MACLEAN@SEL$1

Note
-----
   - dynamic sampling used for this statement

24 rows selected.

/* 也可以从 dba_hist_sql_plan/dba_hist_sqltext等awr历史视图中直接观察该SQL ID对应的语句 */

SQL> select OPERATION,OPTIONS,OBJECT_NAME from dba_hist_sql_plan where sql_id='8vff23q8qp9fj';

OPERATION                      OPTIONS                        OBJECT_NAME
------------------------------ ------------------------------ -------------------------------
SELECT STATEMENT
SORT                           AGGREGATE
TABLE ACCESS                   FULL                           MACLEAN

Extract SQL Plan from AWR