大家过年好！我是个oracle新手，有个问题感觉想不通，请各位前辈指教，问题如下：

在生产库上监控到一个delete操作引起了大量磁盘排序，感觉很迷惑，在测试环境下做了个测试：

SQL> select tablespace_name,bytes/1024/1024 from dba_temp_files;
 
TABLESPACE_NAME                BYTES/1024/1024
------------------------------ ---------------
TEMP2                                      200
TEMP                                         2

SQL> alter database default temporary tablespace temp2;
 
Database altered.
 
SQL>  select count(*) from test;
 
  COUNT(*)
----------
    200000
 
SQL> select count(distinct object_id) from test;
 
COUNT(DISTINCTOBJECT_ID)
------------------------
                  200000
 
SQL> create unique index idx_test1 on test(object_id);
 
Index created.
 
SQL> alter database default temporary tablespace temp;
 
Database altered.
 
SQL> delete from test where object_id>0;
delete from test where object_id>0
            *
ERROR at line 1:
ORA-01652: unable to extend temp segment by 128 in tablespace TEMP

SQL> delete /*+ full(test) */ from test where object_id>0;
 
200000 rows deleted.

显然走索引范围扫描时需要排序，而全表扫描的情况下，是不需要排序。为什么delete时采用了索引范围扫描就需要排序呢，望各位前辈指点迷津，多谢了！