SQL> select rownum rn ,a.* from cnmir.ew_auctions a where rownum<50000;
Execution Plan
----------------------------------------------------------Plan hash value: 721966694----------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |----------------------------------------------------------------------------------| 0 | SELECT STATEMENT | | 49999 | 4833K| 163 (2)| 00:00:02 ||* 1 | COUNT STOPKEY | | | | | || 2 | TABLE ACCESS FULL| EW_AUCTIONS | 49999 | 4833K| 163 (2)| 00:00:02 |----------------------------------------------------------------------------------SQL> select * from cnmir.ew_auctions where issue_id<80;
Execution Plan
----------------------------------------------------------Plan hash value: 518049957---------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |---------------------------------------------------------------------------------| 0 | SELECT STATEMENT | | 1 | 99 | 1379 (2)| 00:00:17 ||* 1 | TABLE ACCESS FULL| EW_AUCTIONS | 1 | 99 | 1379 (2)| 00:00:17 |---------------------------------------------------------------------------------可见COUNT STOPKEY 机制是只针对rownum而设定的!