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; (which is exactly what your hack does) but we don't allow that: you can only lock tables. I wonder what's the reason for that restriction. AFAICT changing it is trivial, since it just requires a very minor change in RangeVarCallbackForLockTable() to allow views. > Is there a clean way to achieve it without the "hack"? I can't think of anything. -- Álvaro Herrera https://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services -- Sent via pgsql-admin mailing list (pgsql-admin@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-admin
