Re: Review: Non-inheritable check constraints

Hi,

> There is at least one other
> problem. Consider:
>
> rhaas=# create table a (ff1 int, constraint chk check (ff1 > 0));
> CREATE TABLE
> rhaas=# create table b (ff1 int, constraint chk check (ff1 > 0));
> CREATE TABLE
> rhaas=# alter table b inherit a;
> ALTER TABLE
>
> This needs to fail if chk is an "only" constraint, but it doesn't,
> even with this patch.
>
>
As you rightly point out, this is because we cannot specify ONLY
constraints inside a CREATE TABLE as of now.

> I think that part of the problem here is fuzzy thinking about the
> meaning of the word "ONLY" in "ALTER TABLE ONLY b". The word "ONLY"
> there is really supposed to mean that the operation is performed on b
> but not on its descendents; but that's not what you're doing: you're
> really performing a different operation. In theory, for a table with
> no current descendents, ALTER TABLE ONLY b and ALTER TABLE b ought to
> be identical, but here they are not. I think that's probably bad.
>
>
ONLY has inheritance based connotations for present/future children. ALTER
ONLY combined with ADD is honored better now with this patch IMO (atleast
for constraints I think).

> Another manifestation of this problem is that there's no way to add an
> ONLY constraint in a CREATE TABLE command. I think that's bad, too:
> it should be possible to declare any constraint at table creation
> time, and if the ONLY were part of the constraint definition rather
> than part of the target-table specification, that would work fine. As
> it is, it doesn't.
>
>
Well, the above was thought about during the original discussion and
eventually we felt that CREATE TABLE already has other issues as well, so
not having this done as part of creating a table was considered acceptable:

http://postgresql.1045698.n5.nabble.com/Check-constraints-on-partition-parents-only-tt4633334.html#a4647144

> I am tempted to say we should revert this and rethink. I don't
> believe we are only a small patch away from finding all the bugs here.
>
>
Sure, if we all think that CREATE TABLE should support ONLY CONSTRAINT type
of syntax, then +1 for reverting this and a subsequent revised submission.

Regards,
Nikhils