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

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


-- 
Adrian Klaver
adrian.klaver@aklaver.com