On Wed, Jul 19, 2017 at 01:12:02PM -0400, Tom Lane wrote:
> Robert Haas <robertmh...@gmail.com> writes:
> > On Mon, Jul 17, 2017 at 6:12 PM, Tom Lane <t...@sss.pgh.pa.us> wrote:
> >> So, thinking about how that would actually work ... the thing to do in
> >> order to preserve existing on-disk values is to alternate between signed
> >> and unsigned interpretations of abstimes.  That is, right now, abstime
> >> is signed with origin 1970.  The conversion I'm arguing we should make
> >> real soon now is to unsigned with origin 1970.  If the project lives
> >> so long, in circa 70 years we'd switch it to signed with origin 2106.
> >> Yadda yadda.
> > Doesn't this plan amount to breaking pg_upgrade compatibility and
> > hoping that nobody notice?
> Well, what we'd need to do is document that the type is only meant to be
> used to store dates within say +/- 30 years from current time.  As long
> as people adhere to that use-case, the proposal would work conveniently
> long into the future ...
> > If we had two actually
> > separate types and let people convert columns from the old type to the
> > new type with just a validation scan, that would be engineering at the
> > level of quality that I've come to associate with this project.
> ... whereas that would be seriously INconvenient.  It's not just the
> ALTER TABLE pushups, which presumably would be something you could do
> and forget.  It's that the new type name would be something you'd have
> to change your applications to know about, and then you (or more likely
> your successor) would have to do it over again decades later.
> I'd definitely be on board with just dropping the type altogether despite
> Mark's concern.  But I am not sure that the way you are proposing would
> please anybody except pedants.

+1 for just dropping the types, preferably modifying the contrib
extensions that depend on it, less preferably, dropping those, too.

David Fetter <david(at)fetter(dot)org> http://fetter.org/
Phone: +1 415 235 3778  AIM: dfetter666  Yahoo!: dfetter
Skype: davidfetter      XMPP: david(dot)fetter(at)gmail(dot)com

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