On Thu, Sep 12, 2013 at 10:03 PM, <wangshuo@highgo.com.cn> wrote:
> Second, I tested the check and the foreign key constraint as your test
> above.
> And no error found, as fellow:
You're missing the point. Peter wasn't worried that your patch throws
an error; he's concerned about the fact that it doesn't.
In PostgreSQL, you can only create the following view because test1
has a primary key over column a:
=> create table test1 (a int constraint pk primary key, b text);
=> create view test2 as select a, b from test1 group by a;
=> alter table test1 drop constraint pk;
The reason that, if the primary key weren't there, it would be
ambiguous which row should be returned as among multiple values where
a is equal and b is not. If you can disable the constraint, then you
can create precisely that problem.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
