Thread: Can you make a simple view non-updatable?

Zitat von Ryan Murphy <ryanfmurphy@gmail.com>:

> Is there any way to set a VIEW to be read-only -- specifically, can I do
> this for a view that is automatically updatable due to being simple?

Without saying anything about if this is directly possible, using  
different users with appropriate grants Comes to my mind, i. e. maybe  
it is time to overhaul the security concept.


Cheer, Thiemo

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maybe it is time to overhaul the security concept.

I could see how I could revoke permissions from, say, all users that aren't superusers to INSERT or UPDATE certain views.  However, if possible it would be nice to get an error message about the VIEW not being updatable, rather than a user access error, which could be misleading.

When I try to insert into a non-updatable VIEWs, I get this message:

ERROR:  cannot insert into view "test_view"

DETAIL:  Views containing GROUP BY are not automatically updatable.
HINT:  To enable inserting into the view, provide an INSTEAD OF INSERT trigger or an unconditional ON INSERT DO INSTEAD rule.

It would be great to see something like this when trying to insert into a simple VIEW that I had made non-updatable:

ERROR:  cannot insert into view "test_view2"

DETAIL:  This view has manually been made non-updatable.

Zitat von Ryan Murphy <ryanfmurphy@gmail.com>:

> I could see how I could revoke permissions from, say, all users that aren't
> superusers to INSERT or UPDATE certain views.  However, if possible it
> would be nice to get an error message about the VIEW not being updatable,
> rather than a user access error, which could be misleading.

I feel it would be the other way round. If you deny something that is
technically possible, I would be puzzled to get an error about a
technical impossibility. If you want to stop people updating a view,
in my opion, it is very well to tell them they are not allowed to and
not that it isn't technically possible. So there can start a
discussion whether they are rightfully denied to update data therein,
instead of first discussing why it is not technically possible to
update to find out it IS technically possible but it was actually
denied.

> When I try to insert into a non-updatable VIEWs, I get this message:
>
> ERROR:  cannot insert into view "test_view"
> DETAIL:  Views containing GROUP BY are not automatically updatable.
> HINT:  To enable inserting into the view, provide an INSTEAD OF INSERT
> trigger or an unconditional ON INSERT DO INSTEAD rule.
>
> It would be great to see something like this when trying to insert into a
> simple VIEW that I had made non-updatable:
>
> ERROR:  cannot insert into view "test_view2"
> DETAIL:  This view has manually been made non-updatable.

You still could put a trigger on the views throwing according
exceptions for specific users. I think I partly used that already but
can't find the code at the moment.



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On 06/08/2018 01:38 AM, Ryan Murphy wrote:
> Hello.
> 
> I enjoy using VIEWs.  Often my views are updatable, either automatically 
> (due to being a simple 1-table view, or due to a TRIGGER).  Sometimes 
> they are meant to be just read-only.
> 
> Is there any way to set a VIEW to be read-only -- specifically, can I do 
> this for a view that is automatically updatable due to being simple?

Using INSTEAD OF trigger?:

create view ct_vw as select * from container;

insert into ct_vw (c_id, cdesc, cell_per, c_size, c_units) values 
('test', 'test container', 1, 2, 4);
INSERT 1836533 1


CREATE OR REPLACE FUNCTION public.vw_ro()
  RETURNS trigger
  LANGUAGE plpgsql
AS $function$
BEGIN
     RAISE NOTICE 'Read only view';
     RETURN NULL;
END;
$function$

CREATE TRIGGER ro_trg INSTEAD OF INSERT or UPDATE or DELETE ON ct_vw FOR 
EACH ROW EXECUTE  procedure vw_ro();

insert into ct_vw (c_id, cdesc, cell_per, c_size, c_units) values 
('test', 'test container', 1, 2, 4);
NOTICE:  Read only view
INSERT 0 0

update ct_vw set cell_per = 100 where c_id = '200PT';
NOTICE:  Read only view
UPDATE 0

delete from ct_vw where c_id = '200PT';
NOTICE:  Read only view
DELETE 0


> 
> The reason I want this:  It will help me encode into my schema the 
> distinction between views that are supposed to behave like full-fledged 
> "subtypes" of a larger relation and need to be updatable, vs those that 
> are merely a report / literally just a "view".
> 
> Thanks!
> Ryan


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Adrian Klaver
adrian.klaver@aklaver.com