And yeah, certainly there's a bug as you point out. postgres=# create table a1 (ff1 int, constraint chk check (ff1 > 0)); postgres=# create table b1 (ff1 int); postgres=# alter table only b1 add constraint chk check (ff1 > 0); postgres=# alter table b1 inherit a1;
The last command should have refused to inherit. Regards, Nikhils On Fri, Dec 23, 2011 at 8:55 AM, Nikhil Sontakke <nikkh...@gmail.com> wrote: > 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 >
