adative cursor sharing 自己测试脚本
建立测试表：
create table acsdemo1 as select * from all_objects ;
SQL> select count(*) from acsdemo1 ;
COUNT(*)
----------
72189
设置倾斜数据 ， 10 和 9 ， 9 只有一条
QL> update acsdemo1 set object_id = 10 where rownum < 72189 ;
72188 rows updated
SQL> commit;
Commit complete
SQL> update acsdemo1 set object_id = 9 where object_id != 10 ;
1 row updated
SQL> commit;
Commit complete
SQL>
建立索引；
create index ind_acsdemoid on acsdemo1 ( object_id) ;
分析表，并建立直方图：
exec DBMS_STATS.GATHER_TABLE_STATS( OwnName => 'SCOTT' ,TabName => 'ACSDEMO1',Estimate_Percent => 100 ,Cascade => TRUE ,No_Invalidate => FALSE,method_opt => 'for all indexed columns');
查询直方图：
SQL> select * from user_histograms where table_name = 'ACSDEMO1' ;
TABLE_NAME COLUMN_NAME ENDPOINT_NUMBER ENDPOINT_VALUE ENDPOINT_ACTUAL_VALUE
------------------------------ -------------------------------------------------------------------------------- --------------- -------------- --------------------------------------------------------------------------------
ACSDEMO1 OBJECT_ID 1 9
ACSDEMO1 OBJECT_ID 72189 10
SQL> select * from user_tab_histograms where table_name = 'ACSDEMO1' ;
TABLE_NAME COLUMN_NAME ENDPOINT_NUMBER ENDPOINT_VALUE ENDPOINT_ACTUAL_VALUE
------------------------------ -------------------------------------------------------------------------------- --------------- -------------- --------------------------------------------------------------------------------
ACSDEMO1 OBJECT_ID 1 9
ACSDEMO1 OBJECT_ID 72189 10
SQL>
进行三次 查询， 第一次 9 ， 第二次， 第三次 10 ： autotrace 出来 ：
必须是 绑定变量 , 所以不能用普通的脚本，要使用绑定变量来进行，同时 脚本必须完全相同 ：
exec :oid := 10 ;
select count(*) , max(object_id) from acsdemo1 where object_id = :oid;
select count(*) , max(object_id) from acsdemo1 where object_id = :oid;
SQL> select * from v$sql where sql_text like '%acsdemo1%' ;
SQL_TEXT SQL_FULLTEXT SQL_ID
-------------------------------------------------------------------------------- -------------------------------------------------------------------------------- -------------
select * from v$sql where sql_text like '%acsdemo1%' select * from v$sql where sql_text like '%acsdemo1%' 5tmx859jruxcy
select count(*) , max(object_id) from acsdemo1 where object_id = :oid select count(*) , max(object_id) from acsdemo1 where object_id = :oid 6wqm8dsh83zcg
select count(*) , max(object_id) from acsdemo1 where object_id = :oid select count(*) , max(object_id) from acsdemo1 where object_id = :oid 6wqm8dsh83zcg
SQL>
运行sql ：
var oid number ;
exec :oid := 9 ;
select count(*) , max(object_id) from acsdemo1 where object_id = :oid;
exec :oid := 10 ;
select count(*) , max(object_id) from acsdemo1 where object_id = :oid;
exec :oid := 20 ;
select count(*) , max(object_id) from acsdemo1 where object_id = :oid;
exec :oid := 9 ;
select count(*) , max(object_id) from acsdemo1 where object_id = :oid;
SQL> select a.SQL_ID, a.CHILD_NUMBER , a.EXECUTIONS , a.BUFFER_GETS , a.IS_BIND_SENSITIVE , a.IS_BIND_AWARE , a.IS_SHAREABLE from v$sql a where a.SQL_ID in ('6wqm8dsh83zcg' ) ;
SQL_ID CHILD_NUMBER EXECUTIONS BUFFER_GETS IS_BIND_SENSITIVE IS_BIND_AWARE IS_SHAREABLE
------------- ------------ ---------- ----------- ----------------- ------------- ------------
6wqm8dsh83zcg 0 2 396 Y N N
6wqm8dsh83zcg 1 18 2682 Y Y Y
6wqm8dsh83zcg 2 3 6 Y Y N
6wqm8dsh83zcg 3 10 20 Y Y Y
SQL>
必须使用这个：
select * from table(dbms_xplan.display_cursor('6wqm8dsh83zcg',1 ));
分别查询 出各个子游标对应的 执行计划
SQL> select * from table(dbms_xplan.display_cursor('6wqm8dsh83zcg',0 ));
PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
SQL_ID 6wqm8dsh83zcg, child number 0
-------------------------------------
select count(*) , max(object_id) from acsdemo1 where object_id = :oid
Plan hash value: 1278124634
--------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time
--------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | | | 1 (100)|
| 1 | SORT AGGREGATE | | 1 | 3 | |
|* 2 | INDEX RANGE SCAN| IND_ACSDEMOID | 1 | 3 | 1 (0)| 00:00:0
--------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
2 - access("OBJECT_ID"=:OID)
19 rows selected
SQL> select * from table(dbms_xplan.display_cursor('6wqm8dsh83zcg',1 ));
PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
SQL_ID 6wqm8dsh83zcg, child number 1
-------------------------------------
select count(*) , max(object_id) from acsdemo1 where object_id = :oid
Plan hash value: 1645313489
--------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Tim
--------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | | | 41 (100)|
| 1 | SORT AGGREGATE | | 1 | 3 | |
|* 2 | INDEX FAST FULL SCAN| IND_ACSDEMOID | 72188 | 211K| 41 (3)| 00:
--------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
2 - filter("OBJECT_ID"=:OID)
19 rows selected
SQL> select * from table(dbms_xplan.display_cursor('6wqm8dsh83zcg',2 ));
PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
SQL_ID 6wqm8dsh83zcg, child number 2
-------------------------------------
select count(*) , max(object_id) from acsdemo1 where object_id = :oid
Plan hash value: 1278124634
--------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time
--------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | | | 1 (100)|
| 1 | SORT AGGREGATE | | 1 | 3 | |
|* 2 | INDEX RANGE SCAN| IND_ACSDEMOID | 1 | 3 | 1 (0)| 00:00:0
--------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
2 - access("OBJECT_ID"=:OID)
19 rows selected
SQL> select * from table(dbms_xplan.display_cursor('6wqm8dsh83zcg',3 ));
PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
SQL_ID 6wqm8dsh83zcg, child number 3
-------------------------------------
select count(*) , max(object_id) from acsdemo1 where object_id = :oid
Plan hash value: 1278124634
--------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time
--------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | | | 1 (100)|
| 1 | SORT AGGREGATE | | 1 | 3 | |
|* 2 | INDEX RANGE SCAN| IND_ACSDEMOID | 1 | 3 | 1 (0)| 00:00:0
--------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
2 - access("OBJECT_ID"=:OID)
19 rows selected
SQL>
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转载于:http://blog.itpub.net/16993226/viewspace-774228/