On January 28, 2005 03:46 pm, Fiel Cabral wrote:
> 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?
You use pg_dump -s   (schema only no data).  slony will populate the table 
with data.

>
> 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...
>
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Darcy Buskermolen
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