Re: ENABLE/DISABLE CONSTRAINT NAME

On Tue, Sep 24, 2013 at 5:58 AM, Bernd Helmle <mailings@oopsware.de> wrote:
> --On 13. September 2013 20:17:19 -0400 Robert Haas <robertmhaas@gmail.com>
> wrote:
>> 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.
>
> Hmm not sure i understand this argument either: this patch doesn't allow
> disabling a primary key. It only supports FKs and CHECK constraints
> explicitly.

Well, that is certainly one way of skating around the specific concern
Peter raised.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company