Re: Lock a viewe

Hi,

Have you tried,

https://wiki.postgresql.org/wiki/Lock_Monitoring
https://www.postgresql.org/docs/9.1/static/explicit-locking.html
https://www.postgresql.org/docs/9.1/static/sql-lock.html

Regards

2016-12-20 16:17 GMT-04:00 Gaetano Mendola <mendola(at)gmail(dot)com>:

> 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.
>
> Is there a clean way to achieve it without the "hack"?
>
>
> GM
>
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