Question

SELECT COUNT (*)
  FROM rps2_workflow
 WHERE     workflow_added > TO_DATE ('01.09.2011', 'dd.mm.yyyy')
       AND workflow_finished < TO_DATE ('wtf', 'dd.mm.yyyy')
       AND workflow_status IN (7, 12, 17)
       AND workflow_worker = 159

我希望此查询失败，因为日期无效，但它返回0

此查询的计划显示，在第8步，无效条款已处理：

8 TABLE ACCESS BY INDEX ROWID TABLE RPS2.RPS2_WORKFLOW Object Instance: 1  Filter Predicates: ("WORKFLOW_STATUS"=7 OR "WORKFLOW_STATUS"=12 OR "WORKFLOW_STATUS"=17) AND SYS_EXTRACT_UTC("WORKFLOW_FINISHED")<SYS_EXTRACT_UTC(TO_DATE('wtf','dd.mm.yyyy'))  Cost: 11  Bytes: 33  Cardinality: 1  CPU Cost: 8 M  IO Cost: 10  Time: 1

如果我们评论AND workflow_status IN (7, 12, 17)条件 - 那么我们应该得到ORA-01858: a non-numeric character was found where a numeric was expected

如果我们注释掉AND workflow_finished < TO_DATE ('wtf', 'dd.mm.yyyy')，那么我们会得到符合条件的记录数量（＆gt; 0）

这怎么可能？

UPD ：

提示/*+no_index(rps2_workflow) */不会改变任何内容（而在计划中我们看到执行了fullscan）

SELECT STATEMENT  ALL_ROWSCost: 254  Bytes: 31  Cardinality: 1  CPU Cost: 34 M  IO Cost: 248  Time: 4       
2 SORT AGGREGATE  Bytes: 31  Cardinality: 1     
    1 TABLE ACCESS FULL TABLE RPS2.RPS2_WORKFLOW Object Instance: 1  Filter Predicates: "WORKFLOW_WORKER"=159 AND ("WORKFLOW_STATUS"=7 OR "WORKFLOW_STATUS"=12 OR "WORKFLOW_STATUS"=17) AND SYS_EXTRACT_UTC("WORKFLOW_ADDED")>SYS_EXTRACT_UTC(TIMESTAMP' 2011-09-01 00:00:00') AND SYS_EXTRACT_UTC("WORKFLOW_FINISHED")<SYS_EXTRACT_UTC(TO_DATE('wtf','dd.mm.yyyy'))  Cost: 254  Bytes: 31  Cardinality: 1  CPU Cost: 34 M  IO Cost: 248  Time: 4

Answer 1

如果优化器决定它不需要评估函数，它就不会，所以函数永远不会抛出异常：

select 1 from dual where 1 = 1 OR to_date('asdasdasd','asdasdasdas') > sysdate ;

         1
----------
         1

该函数仅在实际得到评估时引发异常：

SQL> select 1 from dual where 1 = 1 AND to_date('asdasd','asdas') > sysdate ;
select 1 from dual where 1 = 1 AND to_date('asdasd','asdas') > sysdate
                                                    *
ERROR at line 1:
ORA-01821: date format not recognized

但是，如果解析器可以判断静态该查询是无效的 - 因为该函数具有错误类型的参数或者查询具有无效类型，则解析器将在优化器之前引发异常得到一个摆动：

SQL> select 1 from dual where 1 = 1 or to_date('asdasdasd',0) > sysdate ;
select 1 from dual where 1 = 1 or to_date('asdasdasd',0) > sysdate
                                                         *
ERROR at line 1:
ORA-00932: inconsistent datatypes: expected DATE got NUMBER


SQL> select 1 from dual where 1 = 1 or to_date('asdasdasd','asdasdasdas') > 42 ;
select 1 from dual where 1 = 1 or to_date('asdasdasd','asdasdasdas') > 42
                                                                        *
ERROR at line 1:
ORA-00932: inconsistent datatypes: expected DATE got NUMBER

Answer 2

可能发现满足所有其他条件的每条记录都有一个NULL workflow_finished字段。

与NULL进行比较的任何内容都是未知的，因此不需要评估其他操作数。

意外查询成功

2 个答案: