Re: Materialized views vs. primary keys

On 2016/04/06 8:48, David Fetter wrote:
> On Tue, Apr 05, 2016 at 07:10:56PM -0400, Robert Haas wrote:
>> On Tue, Apr 5, 2016 at 6:50 PM, David Fetter <david(at)fetter(dot)org> wrote:
>>> Is there a reason other than lack of tuits for this restriction?
>>
>> "this" lacks an antecedent.
>
> Try to put a primary key on a materialized view, for example:
>
> CREATE TABLE foo(id SERIAL PRIMARY KEY, t text);
>
> CREATE MATERIALIZED VIEW bar AS SELECT * FROM foo;
>
> REFRESH MATERIALIZED VIEW bar;
>
> ALTER MATERIALIZED VIEW bar ADD PRIMARY KEY(id);
>
> At that last step, you get an error that bar is not a table. You get
> an identical error with the hoary old trick of
>
> ALTER TABLE bar ADD PRIMARY KEY(id);

Initially I thought it may be just an oversight of forgetting to pass
ATT_MATVIEW to ATSimplePermissions() in ALTER TABLE processing and that
there are no deeper technical reasons why that is so. But, there seem to
be. On inspecting a little, it seems I can create unique indexes on a
matview, but couldn't manage to set its columns to NOT NULL. Only allowed
relations in the latter case are plain tables and foreign tables. I guess
that follows from how NOT NULL constraints are enforced.

> This lack prevents things that depend on primary keys (foreign keys,
> logical replication, etc.) from operating on the materialized views.

Thanks,
Amit