Oracle 锁定临时表统计信息及锁住后是否能用动态采集的hint

  全局临时表的统计信息是不能被收集的，如果被收集，它的统计信息肯定为0，会造成执行计划不准，所以要锁定它的统计信息，禁止系统自动收集。

--先解锁表的统计信息，然后删除表的统计信息，最后锁住表的统计信息

declare
  v_sqlvarchar2(500);
 
cursor rowList1 is
  
select'begin dbms_stats.unlock_table_stats(user,''' || table_name ||'''); end;'
    
from user_tables s
  
where s.temporary =
'Y'; 
 
cursor rowList2 is
  
select'begin dbms_stats.delete_table_stats(user,''' || table_name ||'''); end;'
    
from user_tables s
  
where s.temporary =
'Y';
 
cursor rowList3 is
  
select'begin dbms_stats.lock_table_stats(user,''' || table_name ||'''); end;'
    
from user_tables s
  
where s.temporary =
'Y';  
begin
 
open rowList1;
 
open rowList2;
 
open rowList3;
 
loop
   
fetch rowList1  into v_sql;
      
executeimmediate v_sql;
   
exitwhen rowList1%notfound;
 
endloop;
 
loop
   
fetch rowList2  into v_sql;
      
executeimmediate v_sql;
   
exitwhen rowList2%notfound;
 
endloop;
 
loop
   
fetch rowList3  into v_sql;
      
executeimmediate v_sql;
   
exitwhen rowList3%notfound;
 
endloop;   
 
close rowList1;
 
close rowList2;
 
close rowList3;
end;
-- STATTYPE_LOCKED='ALL'意思是表的统计信息被锁

select s.table_name,s.STATTYPE_LOCKED  from user_TAB_STATISTICS s  where
s.STATTYPE_LOCKED='ALL';
--当表的统计信息被锁后，用动态采集的hint是否生效，实验结果是hint是生效的
SQL> drop table test purge;

SQL> create table test as select * from dba_objects;

SQL> exec dbms_stats.lock_table_stats(user,'test');

SQL> select s.num_rows, s.last_analyzed

      from user_tables s

     where s.table_name = 'TEST';

  NUM_ROWS LAST_ANALYZED

---------- --------------
--说明表被锁了

SQL> select s.STATTYPE_LOCKED from user_TAB_STATISTICS s

     where s.table_name='TEST';

STATTYPE_L

----------

ALL

SQL> select count(*) from test;

  COUNT(*)

----------

     70384

SQL> set autotrace traceonly

SQL> select /*+ dynamic_sampling(test 1) */ * from test;

已选择70384行。

执行计划

----------------------------------------------------------

Plan hash value: 1357081020

--------------------------------------------------------------------------

| Id  | Operation         | Name | Rows  | Bytes | Cost (%CPU)| Time     |

--------------------------------------------------------------------------

|   0 | SELECT STATEMENT  |      |   160K|    31M|   199   (3)| 00:00:03 |

|   1 |  TABLE ACCESS FULL| TEST |   160K|    31M|   199   (3)| 00:00:03 |

--------------------------------------------------------------------------

Note

-----

   - dynamic sampling used for this statement (level=2)

统计信息

----------------------------------------------------------

          4  recursive calls

          0  db block gets

       5239  consistent gets

          0  physical reads

          0  redo size

    3186713  bytes sent via SQL*Net to client

      51949  bytes received via SQL*Net from client

       4694  SQL*Net roundtrips to/from client

          0  sorts (memory)

          0  sorts (disk)

      70384  rows processed

SQL> select /*+ dynamic_sampling(test 5) */ * from test;

已选择70384行。

执行计划

----------------------------------------------------------

Plan hash value: 1357081020

--------------------------------------------------------------------------

| Id  | Operation         | Name | Rows  | Bytes | Cost (%CPU)| Time     |

--------------------------------------------------------------------------

|   0 | SELECT STATEMENT  |      |  9747 |  1970K|   195   (0)| 00:00:03 |

|   1 |  TABLE ACCESS FULL| TEST |  9747 |  1970K|   195   (0)| 00:00:03 |

--------------------------------------------------------------------------

Note

-----

   - dynamic sampling used for this statement (level=2)

统计信息

----------------------------------------------------------

          4  recursive calls

          0  db block gets

       5239  consistent gets

          0  physical reads

          0  redo size

    3186713  bytes sent via SQL*Net to client

      51949  bytes received via SQL*Net from client

       4694  SQL*Net roundtrips to/from client

          0  sorts (memory)

          0  sorts (disk)

      70384  rows processed

SQL> select /*+ dynamic_sampling(test 10) */ * from test;

已选择70384行。

执行计划

----------------------------------------------------------

Plan hash value: 1357081020

--------------------------------------------------------------------------

| Id  | Operation         | Name | Rows  | Bytes | Cost (%CPU)| Time     |

--------------------------------------------------------------------------

|   0 | SELECT STATEMENT  |      | 70384 |    13M|   197   (2)| 00:00:03 |

|   1 |  TABLE ACCESS FULL| TEST | 70384 |    13M|   197   (2)| 00:00:03 |

--------------------------------------------------------------------------

Note

-----

   - dynamic sampling used for this statement (level=2)

统计信息

----------------------------------------------------------

          0  recursive calls

          0  db block gets

       5165  consistent gets

          0  physical reads

          0  redo size

    3186713  bytes sent via SQL*Net to client

      51949  bytes received via SQL*Net from client

       4694  SQL*Net roundtrips to/from client

          0  sorts (memory)

          0  sorts (disk)

      70384  rows processed