On Fri, Feb 26, 2016 at 7:21 PM, Oleg Bartunov <obartunov@gmail.com> wrote:
> Right now tm is hardcoded and it's doesn't matter "if other people might
> need" at all. We at least provide developers ("other people") ability to
> work on their implementations and the patch is safe and doesn't sacrifices
> anything in core.
I don't believe that. When we install APIs into core, we're
committing to keep those APIs around. And I think that we're far too
early in the development of transaction managers for PostgreSQL to
think that we know what APIs we want to commit to over the long term.
>> And what makes us think we
>> really need multiple transaction managers, anyway?
>
> If you brave enough to say that one tm-fits-all and you are able to teach
> existed tm to play well in various clustering environment during
> development period, which is short, than probably we don't need multiple
> tms. But It's too perfect to believe and practical solution is to let
> multiple groups to work on their solutions.
Nobody's preventing multiple groups for working on their solutions.
That's not the question. The question is why we should install hooks
in core at this early stage without waiting to see which
implementations prove to be best and whether those hooks are actually
general enough to cater to everything people want to do. There is
talk of integrating XC/XL work into PostgreSQL; it has a GTM.
Postgres Pro has several GTMs. Maybe there will be others.
Frankly, I'd like to see a GTM in core at some point because I'd like
everybody who uses PostgreSQL to have access to a GTM. What I don't
want is for every PostgreSQL company to develop its own GTM and
distribute it separately from everybody else's. IIUC, MySQL kinda did
that with storage engines and it resulted in the fragmentation of the
community. We've had the same thing happen with replication tools -
every PostgreSQL company develops their own set. It would have been
better to have ONE set that was distributed by the core project so
that we didn't all do the same work over again.
I don't understand the argument that without these hooks in core,
people can't continue to work on this. It isn't hard to work on GTM
without any core changes at all. You just patch your copy of
PostgreSQL. We do this all the time, for every patch. We don't add
hooks for every patch.
> dtms. It's time to start working on dtm, I believe. The fact you don't
> think about distributed transactions support doesn't mean there no "other
> people", who has different ideas on postgres future. That's why we propose
> this patch, let's play the game !
I don't like to play games with the architecture of PostgreSQL.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company