我们需要使用绑定(bind)变量实现查询重写，因为我们没有修改 Web 应用程序源代码的选项。例子:
BEGIN
SYS.DBMS_ADVANCED_REWRITE.declare_rewrite_equivalence (
name => 'test_rewrite2',
source_stmt => 'select COUNT(*) from ViewX where columnA = :1',
destination_stmt => 'select COUNT(*) from ViewY where columnA = :1',
validate => FALSE,
rewrite_mode => 'recursive');
END;
上面的命令会报错，因为有一个绑定(bind)变量:
30353. 00000 - "expression not supported for query rewrite"
*Cause: The SELECT clause referenced UID, USER, ROWNUM, SYSDATE,
CURRENT_TIMESTAMP, MAXVALUE, a sequence number, a bind variable,
correlation variable, a set result, a trigger return variable, a
parallel table queue column, collection iterator, a non-deterministic
date format token RR, etc.
*Action: Remove the offending expression or disable the REWRITE option on
the materialized view.
我正在阅读 here有一个解决方法，但我只是无法在网上的任何地方找到该文档。
你能告诉我周围的工作是什么吗？
最佳答案
您不能指定绑定(bind)参数，但它应该已经按照您的意愿工作了。关键是recursive您作为 mode 传递的参数.recursive和 general模式将拦截所有涉及表(或 View )的语句，忽略过滤器，并将它们转换为以第二个表(或 View )为目标，调整原始语句中的过滤条件 .
(如果您将其定义为 TEXT_MATCH ，它将检查原始语句和目标语句中是否存在相同的过滤器以触发转换。)
在下面的示例中可以看到，即使我们没有定义任何绑定(bind)条件，过滤器 id = 2尽管如此，还是被应用了；换句话说，它实际上正在改变 SELECT * FROM A1 where id = 2进入 SELECT * FROM A2 where id = 2
set LINESIZE 300
drop table A1;
drop view A2;
drop index A1_IDX;
EXEC SYS.DBMS_ADVANCED_REWRITE.drop_rewrite_equivalence (name => 'test_rewrite');
create table A1 (id number, name varchar2(20));
insert into A1 values(1, 'hello world');
insert into A1 values(2, 'hola mundo');
create index A1_IDX on A1(id);
select * from A1;
ALTER SESSION SET QUERY_REWRITE_INTEGRITY = TRUSTED;
CREATE OR REPLACE VIEW A2 AS
SELECT id,
INITCAP(name) AS name
FROM A1
ORDER BY id desc;
BEGIN
SYS.DBMS_ADVANCED_REWRITE.declare_rewrite_equivalence (
name => 'test_rewrite',
source_stmt => 'SELECT * FROM A1',
destination_stmt => 'SELECT * FROM A2',
validate => FALSE,
rewrite_mode => 'recursive');
END;
/
select * from A1;
ID NAME
---------- --------------------
2 Hola Mundo
1 Hello World
select * from A1 where id = 2;
ID NAME
---------- --------------------
2 Hola Mundo
explain plan for
select * from A1 where id = 2;
select * from table(dbms_xplan.display);
PLAN_TABLE_OUTPUT
----------------------------------------------------------------------------------------
Plan hash value: 1034670462
----------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
----------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 25 | 2 (0)| 00:00:01 |
| 1 | VIEW | A2 | 1 | 25 | 2 (0)| 00:00:01 |
| 2 | TABLE ACCESS BY INDEX ROWID | A1 | 1 | 25 | 2 (0)| 00:00:01 |
|* 3 | INDEX RANGE SCAN DESCENDING| A1_IDX | 1 | | 1 (0)| 00:00:01 |
----------------------------------------------------------------------------------------
PLAN_TABLE_OUTPUT
---------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
3 - access("ID"=2)
Note
-----
- dynamic sampling used for this statement (level=2)
- automatic DOP: Computed Degree of Parallelism is 1 because of parallel threshold
20 rows selected
如你看到的
A1 中提取值.它不是盲目地从 A2 中提取所有值然后应用过滤器，因此保留了性能。 关于oracle - 如何将 Oracle DBMS_ADVANCED_REWRITE 与绑定(bind)变量一起使用？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/27387887/