Re: Re: Re:

On Wed, 24 Nov 2021 at 18:18, MichaelDBA <MichaelDBA@sqlexec.com> wrote:
>
> Thanks, Simon, for your continued feedback.
>
> Simon Riggs wrote on 11/24/2021 12:49 PM:
>
> Anyone interested to know more can start here:
> https://www.enterprisedb.com/products/bidirectional-replication-bdr-postgresql-database

You clearly have an interest in BDR, and some knowledge of BDR1, so I
thank you for that.

The limitations of BDR1, written in 2014, are not limitations of the
architecture in general, merely things it didn't do. That has led to
some misunderstandings about what is possible and regrettably some
incorrect points have been made that I've attempted to rebut. Some of
those points relate to how Postgres-XL worked, but are not relevant to
BDR.

7 years later, BDR3 has a significant number of features not present
in BDR1. That may not be as well known, since as you say, BDR3 is not
fully open source. I regret that I was not able to fund further
development of BDR without charging users. Having said that, probably
more than 50% of BDR features are actually open source and part of
PostgreSQL - the contribution of new features has continued with each
new release.

Specific to this conversation, BDR3 supports multiple transaction
modes - with various kinds of consistency. I would point out that
those modes are slower - which is why multiple options are present.
Some modes allow conflicts, some do not.  This has nothing to do with
"Loosely-coupled", which does not present a limitation.

Should a conflict occur, a conflict doesn't *inevitably* cause a
rollback/suspension requiring manual intervention. That doesn't seem
to be a fair characterisation of the current behavior, which again
differs significantly from BDR1. Just like any form of replication,
various actions can cause breakage or difficulties.

Thank you for pointing out deficiencies in the docs. I wrote a large
part of it myself over many years and it seems we haven't yet captured
all of the possible options there.

I'll work on improving the information available to help those
interested in BDR and/or related tech.

-- 
Simon Riggs                http://www.EnterpriseDB.com/