I'm asking because one of the HOWTOs contained this: 
"Slony-I does not yet automatically copy table definitions from a master when a
slave subscribes to it, so we need to import this data.  We do this with
pg_dump."

I have two nodes. Node 1 is the master and it has the database
containing the data to be replicated. Node 2 is the slave and it has
the database with identical table definitions but the tables are all
empty. Is it necessary to run pg_dump to copy the *data* from node 1
to node 2 before initializing node 2 as a slave? Or will slony copy
the data by itself?

Thanks. Have a good weekend.

-Fiel Cabral

On Fri, 28 Jan 2005 17:59:09 -0500, Christopher Browne
<cbbrowne at ca.afilias.info> wrote:
> Fiel Cabral wrote:
> 
> >My question is about this portion of slony-I-failover.txt:
> >
> >
> >>After failover, getting back node1
> >>
> >>
> >
> >
> >
> >>   After the above failover, the data stored on node1 must be
> >>   considered out of sync with the rest of the nodes.  Therefore, the
> >>   only way to get node1 back and transfer the master role to it is
> >>   to rebuild it from scratch as a slave, let it catch up and then
> >>   follow the switchover procedure.
> >>
> >>
> >
> >Is it necesssary to pg_dump the master's DB to the slave's DB in the
> >process of "rebuilding it from scratch as a slave"?
> >
> >Or is it possible to not do the pg_dump and just "let it catch up"?
> >
> >
> Consider the situation of a table that you never update, but rather only
> ever insert to.
> 
> (This is common for transaction tables.)
> 
> If no "dump" of the data from the provider takes place, and all you do
> is to add in the changes, that will NEVER include any of the older records.
> 
> What is done is in fact not a pg_dump, but rather, internally, a
> "COPY_SET" event.
> 
> COPY_SET goes through each of the tables that are being replicated in
> the set, and uses 'COPY table to stdout' to dump the contents of each
> table.  That's kind of analagous to a pg_dump, and there is no choice
> but to do something reasonably similar to that if you actually want a
> consistent replica.
> 
> If you don't care for a consistent replica, I'm not sure what to offer
> you...
>