Oracle中创建包含部分主键的物化视图时无法设置ON COMMIT刷新属性

Question

我需要将作为主键一部分的列的唯一值从表中提取到物化视图中。如果使用“刷新完成”，我可以创建物化视图，但在尝试使用“提交时快速刷新”时却没有运气。谁能指出我是否错过了什么或者Oracle不支持这样的操作。

下面列出了示例输出。谢谢。

SQL> create table TEST( col1 number, col2 number, col3 varchar(32), CONSTRAINT test_pk Primary Key (col1, col2));

Table created.

SQL> create materialized view test_mv build immediate refresh fast on commit as select distinct col2 from test;
create materialized view test_mv build immediate refresh fast on commit as select distinct col2 from test
                                                                                                     *
ERROR at line 1:
ORA-12054: cannot set the ON COMMIT refresh attribute for the materialized view


SQL> create materialized view test_mv build immediate refresh complete as select distinct col2 from test;

Materialized view created.

SQL> drop materialized view test_mv;

Materialized view dropped.

SQL> create materialized view log on test;

Materialized view log created.

SQL> create materialized view test_mv build immediate refresh fast on commit as select distinct col2 from test;
create materialized view test_mv build immediate refresh fast on commit as select distinct col2 from test
                                                                                                     *
ERROR at line 1:
ORA-12054: cannot set the ON COMMIT refresh attribute for the materialized view

Answer 1

您的观点的主要问题是 DISTINCT 子句。提交时快速刷新对底层查询非常敏感。物化视图必须满足许多规则才能支持快速刷新。DISTINCT 可以防止这种情况发生。

您可以使用以下过程检查物化视图的功能DBMS_MVIEW.EXPLAIN_MVIEW：

DECLARE
    result SYS.EXPLAINMVARRAYTYPE := SYS.EXPLAINMVARRAYTYPE();
BEGIN
    DBMS_MVIEW.EXPLAIN_MVIEW('TEST_MV', result);

    FOR i IN result.FIRST..result.LAST LOOP
        DBMS_OUTPUT.PUT_LINE(result(i).CAPABILITY_NAME || ': ' || CASE WHEN result(i).POSSIBLE = 'T' THEN 'Yes' ELSE 'No' || CASE WHEN result(i).RELATED_TEXT IS NOT NULL THEN ' because of ' || result(i).RELATED_TEXT END || '; ' || result(i).MSGTXT END);
    END LOOP;
END;

您可以在文档中找到更多信息http://docs.oracle.com/cd/B28359_01/server.111/b28313/basicmv.htm#i1007007