Re: Re-create dependent views on ALTER TABLE ALTER COLUMN ... TYPE?

On Mon, May 26, 2014 at 06:25:09PM +0400, ash wrote:
> Hi Hackers,
>
> This came up recently on general list (and I've just hit the same issue today):
> http://www.postgresql.org/message-id/CAB7nPqTLmMn1LTb5WE0v0dO57iP0U73yKwzbZytAXDF1CAWLZg@mail.gmail.com
>
> Why couldn't postgres re-create the dependent views automatically? I
> mean it knows which views depend on the altered column and keeps the
> view definition, no?

Also worth considering: functions which take any part of the view as a
parameter.

Not, IMHO, worth considering, are functions like this:

CREATE OR REPLACE FUNCTION make_task_impossible_for_alex()
RETURNS int8
LANGUAGE plpgsql
AS $$
DECLARE
foo text[] := ARRAY['list','of','views','here'];
BEGIN
EXECUTE 'SELECT COUNT(*) FROM %', foo[floor(random()*array_upper(foo,1))];
END;
$$;

That counts pretty strictly as pilot error, not least because it makes
things like you want to write not just hard, but impossible.

> Would a patch likely to be accepted? How hard do you feel this might be
> to implement?

In the general case, impossible. In most sane cases, mostly a matter
of chasing down dependencies, which is harder than it first appears,
as anyone who's worked on that part of pg_dump can tell you.

> Any caveat

Locking. Given that, you'd want this behavior only with CASCADE, per
Stephen's response.

> that defeats the purpose of such feature?

Probably not. I'd certainly like to have the feature :)

Cheers,
David.
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