Hi Peter, I understand what you're pointing at and I agree that it could be a good thing to be able to dump/restore a table without problem.
My point was that check constraints weren't supposed to be used that way theorically (or maybe i'm mistaken ?) so I thought maybe we should just inform the user that this kind of use of a check constraint is a misuse of that feature. Maybe it's not the right way to say it. I can remove the part about pg_dump if it's too confusing... Regards, Lætitia Le mer. 27 juin 2018 à 08:44, Peter Eisentraut < peter.eisentr...@2ndquadrant.com> a écrit : > On 6/26/18 09:49, Lætitia Avrot wrote: > > + <note> > > + <para> > > + Check constraints are not designed to enforce business rules > across tables. > > + Avoid using check constraints with a function accessing other > tables and > > + use <xref linkend="triggers"/> instead. Although PostgreSQL won't > prevent you > > + from doing so, beware that dumps generated by > <application>pg_dump</application> > > + or <application>pg_dumpall</application> may be hard > > + to restore because of such checks, as the underlying dependencies > are not > > + taken into account. > > + </para> > > + </note> > > In a way, I think this is attacking the wrong problem. It is saying > that you should use triggers instead of check constraints in certain > circumstances. But triggers are also used as an implementation detail > of constraints. While it currently doesn't exist, a deferrable check > constraint would probably be implemented as a trigger. It's not the > triggerness that fixes this problem. The problem is more generally that > if a function uses a table, then pg_dump can't know about the ordering. > It happens to work for triggers because triggers are dumped after all > tables, as a performance optimization, and we could very well dump check > constraints differently as well. > > -- > Peter Eisentraut http://www.2ndQuadrant.com/ > PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services > -- *Think! Do you really need to print this email ? * *There is no Planet B.*
