On Fri, Apr 27, 2012 at 11:50 PM, Christopher Browne <cbbrowne@gmail.com> wrote:
> On Fri, Apr 27, 2012 at 4:11 AM, Simon Riggs <simon@2ndquadrant.com> wrote:
>> What I'm hoping to do is to build a basic prototype of logical
>> replication using WAL translation, so we can inspect it to see what
>> the downsides are. It's an extremely non-trivial problem and so I
>> expect there to be mountains to climb. There are other routes to
>> logical replication, with messages marshalled in a similar way to
>> Slony/Londiste/Bucardo/Mammoth(?). So there are options, with
>> measurements to be made and discussions to be had.
>
> I'll note that the latest version of Slony ...has made a substantial change to its data
> representation....
The basic model I'm working to is that "logical replication" will ship
Logical Change Records (LCRs) using the same transport mechanism that
we built for WAL.
How the LCRs are produced and how they are applied is a subject for
debate and measurement. We're lucky enough to have a variety of
mechanisms to compare, Slony 1.0/2.0, Slony 2.2/Londiste/Bucardo and
its worth adding WAL translation there also. My initial thought is
that WAL translation has many positive aspects to it and we are
investigating. There are also some variants on those themes, such as
the one you discussed above.
You probably won't recognise this as such, but I hope that people
might see that I'm hoping to build Slony 3.0, Londiste++ etc. At some
point, we'll all say "thats not Slony", but we'll also say (Josh
already did) "thats not binary replication". But it will be the
descendant of all.
Backwards compatibility is not a goal, please note, but only because
that will complicate matters intensely.
--
Simon Riggs http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
