Re: Lets (not) break all the things. Was: [pgsql-advocacy] 9.6 -> 10.0

On Mon, Apr 11, 2016 at 11:39 AM, Justin Clift <justin@postgresql.org> wrote:
> Moving over a conversation from the pgsql-advocacy mailing list.  In it
> Simon (CC'd) raised the issue of potentially creating a backwards-compatibility
> breaking release at some point in the future, to deal with things that
> might have no other solution (my wording).
>
> Relevant part of that thread there for reference:
>
>   http://www.postgresql.org/message-id/CANP8+jLtk1NtaJyXc=hAqX=0k+ku4zfavgVBKfs+_sOr9hepNQ@mail.gmail.com
>
> Simon included a short starter list of potentials which might be in
> that category:
>
>   * SQL compliant identifiers
>   * Remove RULEs
>   * Change recovery.conf
>   * Change block headers
>   * Retire template0, template1
>   * Optimise FSM
>   * Add heap metapage
>   * Alter tuple headers
>   et al
>
> This still is better placed on -hackers though, so lets have the
> conversation here to figure out if a "backwards compatibility breaking"
> release really is needed or not.

A couple of points here:
*) I don't think having a version number that starts with 10 instead
of 9 magically fixes backwards compatibility problems and I think
that's a dangerous precedent to set unless we're willing to fork
development and support version 9 indefinitely including major release
versions.

*) Compatibility issues at the SQL level have to be taken much more
seriously than other things (like internal layouts or .conf issues).

*) We need to do an honest cost benefit analysis before breaking
things.  Code refactors placed on your users puts an enormous cost
that is often underestimated.  I have some fairly specific examples of
the costs related to the text cast removal for example.  It's not a
pretty picture.

merlin