Re: v10beta pg_catalog diagrams

2017-06-14 19:49 GMT+02:00 Andres Freund <andres(at)anarazel(dot)de>:

> On 2017-06-14 06:05:24 +0200, Pavel Stehule wrote:
> > 2017-06-14 5:53 GMT+02:00 Peter Eisentraut <
> peter(dot)eisentraut(at)2ndquadrant(dot)com
> > >:
> >
> > > On 6/13/17 17:08, Andres Freund wrote:
> > > > I wondered before if we shouldn't introduce "information only"
> > > > unenforced foreign key constraints for the catalogs. We kind of
> > > > manually do that via oidjoins, it'd be nicer if we'd a function
> > > > rechecking fkeys, and the fkeys were in the catalog...
> > >
> > > I don't see why we couldn't just add a full complement of primary and
> > > foreign key constraints (and unique constraints and perhaps some check
> > > constraints). The argument is that they wouldn't normally do anything,
> > > but they would help with documentation and browsing tools, and they
> > > wouldn't hurt anything.
>
> Well, unique constraints are a bit more complicated because they rely on
> an index, and we wouldn't e.g. maintain indexes with WHERE clauses or
> other expressions correctly. I'd be a bit wary of declaring such
> indexes as actually being fully valid, because we have planner logic
> that does planning based on various constraints now, it'd certainly be
> annoying if some "re-check constraint" type queries would actually have
> their joins optimized away or such...
>
> > These constraints can slowdown creating/dropping database objects -
> mainly
> > temp tables.
>
> How so?
>

execution RI triggers

Regards

Pavel

>
> - Andres
>