Excerpts from Nikhil Sontakke's message of vie dic 23 00:25:26 -0300 2011: > 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. No, it's not related to that. You could do it even without that, by creating a table then adding an ONLY constraint and only later doing the ALTER TABLE / INHERIT. The problem we need to fix here is that this command needs to check that there are no unmergeable constraints; and if there are any, error out. > > 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). I agree with Robert that this usage of ALTER TABLE ONLY is slightly different from other usages of the same command, but I disagree that this means that we need another command to do what we want to do here. IOW, I prefer to keep the syntax we have. > > 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. I don't think this is a given ... In fact, IMO if we're only two or three fixes away from having it all nice and consistent, I think reverting is not necessary. -- Álvaro Herrera <alvhe...@commandprompt.com> The PostgreSQL Company - Command Prompt, Inc. PostgreSQL Replication, Consulting, Custom Development, 24x7 support -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
