Re: [PATCH 10/16] Introduce the concept that wal has a 'origin' node

On Wednesday, June 20, 2012 09:23:34 PM Heikki Linnakangas wrote:
> > And then we just put the originid on each heap record for MMR, in some
> > manner, discussed later.
>
> I reserve the right to object to that, too :-). Others raised the
> concern that a 16-bit integer is not a very intuitive identifier. Also,
> as discussed, for more complex scenarios just the originid is not
> sufficient. ISTM that we need more flexibility.
I think the '16bit integer is unintiuitive' argument isn't that interesting.
As pointed out by multiple people in the thread that origin_id can be local
and mapped to something more complex in communication between the different
nodes and the configuration.
Before applying changes from another node you lookup their "complex id" into
the locally mapped 16bit origin_id which then gets written into the wal
stream. When decoding the wal stream into the LCR stream its mapped the other
way.

We might need more information than that at a later point but those probably
won't needed during low-level filtering of wal before reassembling it into
transactions...

Andres

--
Andres Freund http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services