oracle 統計資訊檢視與收集

SQL> alter session set NLS_DATE_FORMAT='YYYY-MM-DD HH24:MI:SS';
SQL> select t.TABLE_NAME,t.NUM_ROWS,t.BLOCKS,t.LAST_ANALYZED from user_tables t where table_name='WOO';

備註：透過指令碼檢視統計資訊,參考MOS：SCRIPT - Select to show Optimizer Statistics for CBO (Doc ID 31412.1)

二、檢視錶上的索引資訊

select table_name,index_name,t.blevel,t.num_rows,t.leaf_blocks,t.last_analyzed 
  from user_indexes t 
  where table_name='DUMP_TABLE';
  
SQL> col table_name format a11
SQL> col index_name format a16
SQL> select table_name,index_name,t.blevel,t.num_rows,t.leaf_blocks,t.last_analyzed 
  2             from user_indexes t 
  3             where table_name='DUMP_TABLE';
TABLE_NAME  INDEX_NAME           BLEVEL   NUM_ROWS LEAF_BLOCKS LAST_ANAL
----------- ---------------- ---------- ---------- ----------- ---------
DUMP_TABLE  WORNUM_IND                0         10           1 18-MAR-20

  
三、檢查當前統計資訊收集策略

set linesize 140
col WINDOW_NAME format a17
col REPEAT_INTERVAL for a55
col DURATION for a15
select t1.window_name,t1.repeat_interval,t1.duration from 
 dba_scheduler_windows t1,dba_scheduler_wingroup_members t2  
 where t1.window_name=t2.window_name 
  and t2.window_group_name 
  in ('MAINTENANCE_WINDOW_GROUP','BSLN_MAINTAIN_STATS_SCHED');
  
  
SQL> set linesize 140
SQL> col WINDOW_NAME format a17
SQL> col REPEAT_INTERVAL for a55
SQL> col DURATION for a15
SQL> select t1.window_name,t1.repeat_interval,t1.duration from 
  2     dba_scheduler_windows t1,dba_scheduler_wingroup_members t2  
  3     where t1.window_name=t2.window_name 
  4             and t2.window_group_name 
  5             in ('MAINTENANCE_WINDOW_GROUP','BSLN_MAINTAIN_STATS_SCHED');
  
WINDOW_NAME       REPEAT_INTERVAL                                         DURATION
----------------- ------------------------------------------------------- ---------------
MONDAY_WINDOW     freq=daily;byday=MON;byhour=22;byminute=0; bysecond=0   +000 04:00:00
TUESDAY_WINDOW    freq=daily;byday=TUE;byhour=22;byminute=0; bysecond=0   +000 04:00:00
WEDNESDAY_WINDOW  freq=daily;byday=WED;byhour=22;byminute=0; bysecond=0   +000 04:00:00
THURSDAY_WINDOW   freq=daily;byday=THU;byhour=22;byminute=0; bysecond=0   +000 04:00:00
FRIDAY_WINDOW     freq=daily;byday=FRI;byhour=22;byminute=0; bysecond=0   +000 04:00:00
SATURDAY_WINDOW   freq=daily;byday=SAT;byhour=6;byminute=0; bysecond=0    +000 20:00:00
SUNDAY_WINDOW     freq=daily;byday=SUN;byhour=6;byminute=0; bysecond=0    +000 20:00:00
7 rows selected.

BEGIN  
 DBMS_SCHEDULER.DISABLE(  
 name => '"SYS"."SATURDAY_WINDOW"',  
 force => TRUE);
END;
/

3.2 修改自動統計資訊持續時間

BEGIN  
 DBMS_SCHEDULER.SET_ATTRIBUTE(  
 name => '"SYS"."SATURDAY_WINDOW"',  
 attribute => 'DURATION',  
 value => numtodsinterval(180,'minute'));
END; 
/

3.3 修改自動統計資訊開始時間，每週六22點開始

BEGIN  
 DBMS_SCHEDULER.SET_ATTRIBUTE(  
 name => '"SYS"."SATURDAY_WINDOW"',  
 attribute => 'REPEAT_INTERVAL',  
 value => 'freq=daily;byday=SAT;byhour=22;byminute=0;bysecond=0 ');
END;
/

3.4 開啟自動統計資訊收集

BEGIN  
 DBMS_SCHEDULER.ENABLE(  
 name => '"SYS"."SATURDAY_WINDOW"');
END;
/

set linesize 200
col REPEAT_INTERVAL for a60
col DURATION for a30
select t1.window_name,t1.repeat_interval,t1.duration 
 from dba_scheduler_windows t1,dba_scheduler_wingroup_members t2
  where t1.window_name=t2.window_name 
   and t2.window_group_name 
   in ('MAINTENANCE_WINDOW_GROUP','BSLN_MAINTAIN_STATS_SCHED');
WINDOW_NAME                    REPEAT_INTERVAL                                              DURATION
------------------------------ ------------------------------------------------------------ ------------------------------
MONDAY_WINDOW                  freq=daily;byday=MON;byhour=22;byminute=0; bysecond=0        +000 04:00:00
TUESDAY_WINDOW                 freq=daily;byday=TUE;byhour=22;byminute=0; bysecond=0        +000 04:00:00
WEDNESDAY_WINDOW               freq=daily;byday=WED;byhour=22;byminute=0; bysecond=0        +000 04:00:00
THURSDAY_WINDOW                freq=daily;byday=THU;byhour=22;byminute=0; bysecond=0        +000 04:00:00
FRIDAY_WINDOW                  freq=daily;byday=FRI;byhour=22;byminute=0; bysecond=0        +000 04:00:00
SATURDAY_WINDOW                freq=daily;byday=SAT;byhour=22;byminute=0;bysecond=0         +000 20:00:00
SUNDAY_WINDOW                  freq=daily;byday=SUN;byhour=6;byminute=0; bysecond=0         +000 20:00:00
7 rows selected.

四、手工收集統計資訊

4.1 收集索引統計資訊

exec dbms_stats.gather_index_stats(ownname => 'WOO',indname => 'WORNUM_IND',estimate_percent => '10',degree => '4');

exec dbms_stats.gather_table_stats(ownname => 'WOO',tabname => 'DUMP_TABLE',estimate_percent => 10,method_opt=> 'for all indexed columns',cascade=>TRUE);

4.3 收集表的統計資訊

exec dbms_stats.gather_table_stats(ownname => 'WOO',tabname => 'DUMP_TABLE',estimate_percent => 10,method_opt=> 'for all indexed columns');

 
 4.4 收集分割槽表統計資訊

exec dbms_stats.gather_table_stats(ownname => 'WOO',tabname => 'DUMP_TABLE',partname => 'p_20190318',estimate_percent => 10,method_opt=> 'for all indexed columns',cascade=>TRUE);

4.5 收集某個使用者的統計資訊

exec dbms_stats.gather_schema_stats(ownname=>'WOO',estimate_percent=>10,degree=>8,cascade=>true,granularity=>'ALL');

exec dbms_stats.gather_database_stats(estimate_percent=>10,degree=>8,cascade=>true,granularity=>'ALL');

五、動態取樣：

SQL> set linesize 200
SQL> set autotrace traceonly
SQL> select  * from DUMP_TABLE;
10 rows selected.
Execution Plan
----------------------------------------------------------
Plan hash value: 1795212136
--------------------------------------------------------------------------------
| Id  | Operation         | Name       | Rows  | Bytes | Cost (%CPU)| Time     |
--------------------------------------------------------------------------------
|   0 | SELECT STATEMENT  |            |    10 | 20390 |     3   (0)| 00:00:01 |
|   1 |  TABLE ACCESS FULL| DUMP_TABLE |    10 | 20390 |     3   (0)| 00:00:01 |
--------------------------------------------------------------------------------
Note
-----
   - dynamic sampling used for this statement (level=2)
Statistics
----------------------------------------------------------
          4  recursive calls
          0  db block gets
          9  consistent gets
          0  physical reads
          0  redo size
       1305  bytes sent via SQL*Net to client
        523  bytes received via SQL*Net from client
          2  SQL*Net roundtrips to/from client
          0  sorts (memory)
          0  sorts (disk)
         10  rows processed

我們們透過user_tables檢視結果也是一樣的

SQL> set autotrace off;
SQL> select num_rows, blocks, last_analyzed from user_tables where table_name = 'DUMP_TABLE';
  NUM_ROWS     BLOCKS LAST_ANAL
---------- ---------- ---------
SQL>

六、統計資訊收集完之後：

SQL> set linesize 200
SQL> set autotrace traceonly
SQL> select  * from DUMP_TABLE;
10 rows selected.
Execution Plan
----------------------------------------------------------
Plan hash value: 1795212136
--------------------------------------------------------------------------------
| Id  | Operation         | Name       | Rows  | Bytes | Cost (%CPU)| Time     |
--------------------------------------------------------------------------------
|   0 | SELECT STATEMENT  |            |    10 |   470 |     3   (0)| 00:00:01 |
|   1 |  TABLE ACCESS FULL| DUMP_TABLE |    10 |   470 |     3   (0)| 00:00:01 |
--------------------------------------------------------------------------------
Statistics
----------------------------------------------------------
         33  recursive calls
          0  db block gets
         56  consistent gets
          0  physical reads
          0  redo size
       1305  bytes sent via SQL*Net to client
        523  bytes received via SQL*Net from client
          2  SQL*Net roundtrips to/from client
          6  sorts (memory)
          0  sorts (disk)
         10  rows processed
         
SQL> set autotrace off;
SQL> alter session set NLS_DATE_FORMAT='YYYY-MM-DD HH24:MI:SS';
SQL> select num_rows, blocks, last_analyzed from user_tables where table_name = 'DUMP_TABLE';
  NUM_ROWS     BLOCKS LAST_ANALYZED
---------- ---------- -------------------
        10          4 2020-03-18 17:06:16
SQL>