Re: Lock a viewe

On Mon, 26 Dec 2016 at 20:53 Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>
wrote:

> Gaetano Mendola wrote:
> > Hi,
> > I was wondering if there is a clean view to lock the usage of a view.
> >
> > Basically during a schema migration, with applications still running a
> > typical
> > schema change is:
> >
> > BEGIN;
> > ALTER TABLE x ADD COLUMN (a INTEGER);
> > CREATE OR REPLACE VIEW v_x
> > AS
> > SELECT a,b FROM x;
> > COMMIT;
> >
> > now the issue is that if an application performs a:
> >
> > SELECT * from v_x;
> >
> > between the ALTER and the view redefinition then a deadlock happens.
> >
> > I'm preventing this issue doing a:
> >
> > ALTER VIEW v_x ALTER COLUMN b DROP DEFAULT;
> > (anyway there was no default on the view)
> > before the ALTER TABLE, that's basically reorders the locks sequence
> > avoiding the dead lock.
>
> So what you want is
> LOCK VIEW f;
>

Exactly that, it would be ideal indeed that was exactly my first attempt.

Regards.