David G Johnston wrote:
> OndÅej Bouda wrote
> > The documentation for ALTER DOMAIN notes that "ALTER DOMAIN ADD CONSTRAINT
> > and ALTER DOMAIN SET NOT NULL will fail if the named domain or any derived
> > domain is used within a composite-type column of any table in the
> > database."
> >
> > It appears current Postgres also fails on ALTER DOMAIN VALIDATE CONSTRAINT
> > in such a case, as demonstrated by the following script:
> TL/DR; The documentation needs some work here; and the code could be more
> helpful - even without overcoming the limitation - though it likely isn't
> worth the effort.
Um. I have vague recollections about going some lengths to make sure
this behaved sanely and usefully, i.e. validate tables that were using
the domains. I guess I didn't cover all bases; seemed difficult enough
as it was, back then. This behavior certainly seems unhelpful, because
in effect you can never get a constraint validated. It doesn't look
unduly complicated to drill down to composite types; maybe a good GSoC
project?
For reference, see this commit, in which Robert's last name was
misspelled once again (sorry about that):
commit 897795240cfaaed724af2f53ed2c50c9862f951f
Author: Alvaro Herrera <alvherre@alvh.no-ip.org>
Date: Wed Jun 1 18:43:50 2011 -0400
Enable CHECK constraints to be declared NOT VALID
This means that they can initially be added to a large existing table
without checking its initial contents, but new tuples must comply to
them; a separate pass invoked by ALTER TABLE / VALIDATE can verify
existing data and ensure it complies with the constraint, at which point
it is marked validated and becomes a normal part of the table ecosystem.
An non-validated CHECK constraint is ignored in the planner for
constraint_exclusion purposes; when validated, cached plans are
recomputed so that partitioning starts working right away.
This patch also enables domains to have unvalidated CHECK constraints
attached to them as well by way of ALTER DOMAIN / ADD CONSTRAINT / NOT
VALID, which can later be validated with ALTER DOMAIN / VALIDATE
CONSTRAINT.
Thanks to Thom Brown, Dean Rasheed and Jaime Casanova for the various
reviews, and Robert Hass for documentation wording improvement
suggestions.
This patch was sponsored by Enova Financial.
--
Ãlvaro Herrera http://www.2ndQuadrant.com/
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