>> If we just had that much in core - that is, the ability to efficiently
>> extra tuple inserts, updates, and deletes on a logical level - it
>> would be much easier to build a good logical replication system around
>> PostgreSQL than it is today, and the existing systems could be adapted
>> to deliver higher performance by making use of the new infrastructure.
Well, this *is* the purpose of the cluster-hackers group, to add backend
support which would make external replication systems easier to build
and more efficient. So far the only real feature to come out of that
has been the Command Triggers, but if you read the TODO list of that
group you'll see that it's a laundry list of things replication systems
need support for in the backend.
http://wiki.postgresql.org/wiki/ClusterFeatures
http://wiki.postgresql.org/wiki/PgCon2012CanadaClusterSummit
What puts me off about this "let's start from first principles" approach
is that in our community we have years of experience (in a couple cases,
over a decade) with logical-level replication. It seems like the last
thing we need is Yet Another PostgreSQL Replication System, started over
from scratch and years away from being production quality. Don't we
have enough external replication systems with not enough developers
behind them?
Even if improving an existing replication system proves to be
impossible, it would make more sense to start with an analysis of the
strengths and deficiencies of Slony, Londiste, Bucardo, etc., than with
some kind of "clean-room" approach.
--
Josh Berkus
PostgreSQL Experts Inc.
http://pgexperts.com