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