FILTER的执行次数和驱动表问题

drop table test1;
create table test1 as select * from dba_objects where rownum<1000;
 
drop table test2;
create table test2 as select * from dba_objects where rownum<1000;
 
insert into test1 select * from test1;
 
update test2 set owner='SCOTT';
 
BEGIN
  DBMS_STATS.GATHER_TABLE_STATS(ownname          => 'SCOTT',
                                tabname          => 'TEST1',
                                estimate_percent => 100,
                                method_opt       => 'for  columns owner size 200',
                                no_invalidate    => FALSE,
                                degree           => 1,
                                cascade          => TRUE);
END;
/
 
BEGIN
  DBMS_STATS.GATHER_TABLE_STATS(ownname          => 'SCOTT',
                                tabname          => 'TEST2',
                                estimate_percent => 100,
                                method_opt       => 'for  columns owner size 200',
                                no_invalidate    => FALSE,
                                degree           => 1,
                                cascade          => TRUE);
END;
/
 
SQL> select * from table(dbms_xplan.display_cursor(null,null,'ALLSTATS LAST'));
 
PLAN_TABLE_OUTPUT
------------------------------------------------------------------------------------------------------------------------------------------------------------
 
--------------------------------------------
SQL_ID	a23r1uchdaafg, child number 0
-------------------------------------
An uncaught error happened in prepare_sql_statement : ORA-01403: no data found
 
Plan hash value: 1896454807
 
--------------------------------------------------------------------------------------
| Id  | Operation	   | Name  | Starts | E-Rows | A-Rows |   A-Time   | Buffers |
--------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT   |	   |	  1 |	     |	 1998 |00:00:00.07 |   13763 |
|*  1 |  FILTER 	   |	   |	  1 |	     |	 1998 |00:00:00.07 |   13763 |
|   2 |   TABLE ACCESS FULL| TEST1 |	  1 |	 999 |	 1998 |00:00:00.01 |	 163 |
|*  3 |   TABLE ACCESS FULL| TEST2 |   1346 |	   1 |	 1346 |00:00:00.06 |   13600 |
--------------------------------------------------------------------------------------
 
Predicate Information (identified by operation id):
---------------------------------------------------
 
   1 - filter(("OWNER"='SCOTT' OR  IS NOT NULL))
   3 - filter(("OWNER"='SCOTT' AND "OBJECT_ID"=:B1))
 
21 rows selected.
 
查看FILTER的执行次数,此时 被驱动表TEST2执行了1346次,那这个1346次是怎么计算的呢？
 
SQL> select count(*) from test1;
 
  COUNT(*)
----------
      1998
 
SQL> select count(distinct object_id) from test1;       
 
COUNT(DISTINCTOBJECT_ID)
------------------------
		     999
 
网上有人说是count(distinct join列),看来结果不对,有待研究
 
FILTER能改变驱动表？
SQL> select /*+ leading(test2)*/ * from test1 where owner='SCOTT' or object_id in(select object_id from test2 where owner='SCOTT')
  2  ;
 
1998 rows selected.
 
Execution Plan
----------------------------------------------------------
Plan hash value: 1896454807
 
----------------------------------------------------------------------------
| Id  | Operation	   | Name  | Rows  | Bytes | Cost (%CPU)| Time	   |
----------------------------------------------------------------------------
|   0 | SELECT STATEMENT   |	   |	52 |  4420 |	 5   (0)| 00:00:01 |
|*  1 |  FILTER 	   |	   |	   |	   |		|	   |
|   2 |   TABLE ACCESS FULL| TEST1 |   999 | 84915 |	 5   (0)| 00:00:01 |
|*  3 |   TABLE ACCESS FULL| TEST2 |	 1 |	18 |	 5   (0)| 00:00:01 |
----------------------------------------------------------------------------
 
FILTER无法改变驱动表
 
1. 减少扫描 次数 
 
2. 无法减少扫描次数，减少扫描体积