Re: [HACKERS] Surjective functional indexes

On 2019-01-14 18:46:18 -0500, Stephen Frost wrote:
> Greetings,
> 
> * Tom Lane (tgl@sss.pgh.pa.us) wrote:
> > Andres Freund <andres@anarazel.de> writes:
> > > On 2019-01-14 18:03:24 -0500, Tom Lane wrote:
> > >> Do we want to revert entirely, or leave the "recheck_on_update" option
> > >> present but nonfunctional?
> > 
> > > I think it depends a bit on whether we want to revert in master or
> > > master and 11. If only master, I don't see much point in leaving the
> > > option around. If both, I think we should (need to?) leave it around in
> > > 11 only.
> > 
> > After a few minutes' more thought, I think that the most attractive
> > option is to leave v11 alone and do a full revert in HEAD.  In this
> > way, if anyone's attached "recheck_on_update" options to their indexes,
> > it'll continue to work^H^H^H^Hdo nothing in v11, though they won't be
> > able to migrate to v12 till they remove the options.  That way we
> > aren't bound to the questionable design and naming of that storage
> > option if/when we try this again.
> 
> So the plan is to add a check into pg_upgrade to complain if it comes
> across any cases where recheck_on_update is set during its pre-flight
> checks..?

I don't think so.

> Or are you suggesting that pg_dump in v12+ would throw errors if it
> finds that set?  Or that we'll dump it, but fail to allow it into a
> v12+ database?  What if v12 sees "recheck_on_update='false'", as a v11
> pg_dump might output today?

It'll just error out on restore (including the internal one by
pg_upgrade). I don't see much point in doing more, this isn't a widely
used option by any stretch.

Greetings,

Andres Freund