为什么 Oracle 同义词会向基础表返回不同数量的行？

Question

我遇到了一个非常不寻常的情况，我希望有人能够阐明这一点。 我对 Oracle 同义词的理解是，它基本上是另一个模式中表的别名。

当我根据同义词进行计数时，它返回零行。 当我对基础表执行相同操作时，它返回 12000 行。

我无法解释这种差异。 有人可以帮忙吗？

select * from dba_synonyms
where synonym_name = 'CS_INCIDENTS_B_SEC';

OWNER  SYNONYM_NAME        TABLE_OWNER  TABLE_NAME          DB_LINK
------ ------------------- ------------ ------------------- -------
APPS   CS_INCIDENTS_B_SEC  CS           CS_INCIDENTS_ALL_B         



select count(*) from CS.CS_INCIDENTS_ALL_B;

COUNT(*)               
---------------------- 
12549                  

select count(*) from APPS.CS_INCIDENTS_B_SEC;

COUNT(*)               
---------------------- 
0                      

解释计划：

直接在表上...

EXPLAIN PLAN FOR
SELECT  *
FROM    CS.CS_INCIDENTS_ALL_B

PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------
| Id  | Operation         | Name               | Rows | Bytes| Cost(%CPU)|
--------------------------------------------------------------------------
|   0 | SELECT STATEMENT  |                    | 6056 | 1549K|  122   (3)|
|   1 |  TABLE ACCESS FULL| CS_INCIDENTS_ALL_B | 6056 | 1549K|  122   (3)|
--------------------------------------------------------------------------

通过同义词...

EXPLAIN PLAN FOR
SELECT  *
FROM    APPS.CS_INCIDENTS_B_SEC

PLAN_TABLE_OUTPUT
---------------------------------------------------------------------------
| Id  | Operation          | Name               | Rows | Bytes| Cost(%CPU)|
---------------------------------------------------------------------------
|   0 | SELECT STATEMENT   |                    |    1 |  262 |    0   (0)|
|*  1 |  FILTER            |                    |      |      |           |
|   2 |   TABLE ACCESS FULL| CS_INCIDENTS_ALL_B | 6056 | 1549K|  122   (3)|
---------------------------------------------------------------------------

1 - filter(NULL IS NOT NULL)

同义词链...

SQL> SELECT  *
  2  FROM    dba_synonyms
  3  START WITH
  4          owner = 'CS'
  5          AND synonym_name = 'CS_INCIDENTS_ALL_B'
  6  CONNECT BY
  7          owner = PRIOR table_owner
  8          AND synonym_name = PRIOR table_name
  9  /

no rows selected

SQL> SELECT  *
  2  FROM    dba_synonyms
  3  START WITH
  4          owner = 'APPS'
  5          AND synonym_name = 'CS_INCIDENTS_B_SEC'
  6  CONNECT BY
  7          owner = PRIOR table_owner
  8          AND synonym_name = PRIOR table_name
  9  /

检查数据库策略...

SQL> SELECT *
  2  FROM dba_policies
  3  WHERE OBJECT_NAME = 'CS_INCIDENTS_B_SEC'
  4  /

OBJECT_OWNER  OBJECT_NAME         POLICY_GROUP  POLICY_NAME          
------------- ------------------- ------------- -------------------- 
APPS          CS_INCIDENTS_B_SEC  SYS_DEFAULT   CS_SR_SEC_SR_ACCESS  


PF_OWNER  PACKAGE            FUNCTION       SEL INS UPD DEL IDX CHK 
--------- ------------------ -------------- --- --- --- --- --- --- 
APPS      FND_GENERIC_POLICY GET_PREDICATE  YES NO  NO  NO  NO  NO  


ENABLE STATIC_POLICY POLICY_TYPE  LONG_PREDICATE
------ ------------- ------------ --------------
YES    NO            DYNAMIC      YES

Answer 1

更新：

您有已启用行级安全性。

每次访问表时都会调用用户函数 FND_GENERIC_POLICY.GET_PREDICATE 并限制对某些行的访问。

它会返回不同的结果，具体取决于您访问表的方式：直接访问或通过SYNONYM。

您需要查看该函数并了解发生了什么（或在此处发布函数文本）。

Answer 2

您是否 100% 确定 CS.CS_INCIDENTS_ALL_B 实际上是表而不是视图？ 如果它是一个视图，也许它在 WHERE 子句中做了一些相当不寻常的事情。

select object_type from dba_objects where owner = 'CS' and object_name = 'CS_INCIDENTS_ALL_B'

Answer 3

检查以确保 APPS 拥有的其他对象（视图或表）没有与您的同义词同名。

select object_type,object_name
from   dba_objects
where  object_name='CS_INCIDENTS_B_SEC'
and    owner='APPS'
and    object_type!='SYNONYM'