The data format is not different between 4.0 and 5.0. The metadata can change, though. We make a best effort for a seamless, automatic upgrade, but you should test your specific scenario yourself to be confident that there are no problems. The larger the version difference, the greater the risk.

On Fri, Jun 14, 2019 at 7:05 AM Josh Elser <elserj@apache.org> wrote:
IIRC, the guidance is that 4.14 should work back to 4.12. We're talking
about minor releases in this case, not bugfix. Every bugfix release
should be compatible within the current minor release. This is one of
the tenants of https://semver.org/

You should not have issues going to 5.0.0, but I don't know of anyone
who has explicitly tested this. You should proceed with caution.

On 6/14/19 2:07 AM, Vova Galchenko wrote:
> Hey Josh,
>
> thanks for getting back to me. The current Phoenix version we're on is
> 4.14.1. Do I understand correctly that the Phoenix community intends to
> provide data compatibility at least two versions back? Does this
> intention apply across major version boundaries? More specifically, does
> it imply that data produced by 4.14.1 is intended to be compatible with
> 4.14.2 and 5.0.0?
>
> Thank you.
>
> vova
>
> On Wed, Jun 12, 2019 at 1:18 PM Josh Elser <elserj@apache.org
> <mailto:elserj@apache.org>> wrote:
>
>     What version of Phoenix 4 are you coming from?
>
>     Of note, if you're lagging far behind, you'll get bit by the column
>     encoding turning on by default in 4.10 [1]
>
>     In general, before we update the system catalog table, we take a
>     snapshot of it, so you can roll back (although this would be
>     manual). In
>     terms of testing as a community, we only do testing back two releases.
>     After that, your mileage may vary.
>
>     - Josh
>
>     [1] https://phoenix.apache.org/columnencoding.html
>
>     On 6/11/19 9:02 PM, Vova Galchenko wrote:
>      > Hello Phoenix Users List!
>      >
>      > We at Box are thinking about the upgrade story from Phoenix 4 to
>     5. As
>      > part of that, we'd like to understand if these Phoenix versions
>     write
>      > data in formats compatible with each other. In other words,
>     suppose we
>      > have an HBase 1.4 cluster used by Phoenix 4. Can I shut
>     everything down,
>      > upgrade HBase to 2.0 and Phoenix to 5, start everything up again,
>     and
>      > expect to preserve the integrity of the data stored in the original
>      > cluster? If not, is there guidance for what the upgrade process
>     might
>      > look like?
>      >
>      > Thanks,
>      >
>      > vova
>