http://www.slony.info/bugzilla/show_bug.cgi?id=69


Christopher Browne <cbbrowne at ca.afilias.info> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|slony1-bugs at lists.slony.info|cbbrowne at ca.afilias.info
           Priority|medium                      |high
           Severity|critical                    |major
             Status|REOPENED                    |NEW




--- Comment #5 from Christopher Browne <cbbrowne at ca.afilias.info>  2008-12-19 13:11:39 ---
That's a VERY good set of observations.

I had a chat with Jan about this, and we see there needing to be a very
specific "upgrade to 2.0" process that will probably not use slonik.

Updating the xxid values into the txid_snapshot type looks to be more than
problematic; I expect that in order to do THAT, we would have to create a set
of xxid-to-txid_snapshot functions, in C, and that feels like just a HORRIBLE
idea.  We moved to txid_snapshot in order to *eliminate* C-based stored
procedures, and this would perpetuate having such a procedure.

What we're contemplating is an "Upgrade Tool" that upgrades the whole cluster
in "one fell swoop."  It would do the following:

1.  Lock all the sets.

2.  Wait for those events to propagate.

Once that has taken place, we can do the xxid-to-snapshot alterations, and
essentially do the same thing that is done at subscription time, namely to set
up sl_set_sync with a fresh SYNC ID.

Thus, we effectively need to reset replication.

It would be really nice to be able to make this process one that could be
rolled back, but I suspect we can't do that too readily.  I think the upgrade
tool will need to do some of its work via running slonik, with the result that
it will have closed some transactions before we get things done.

Thus, the SHORT answer, for now, is that there is not a functioning way to get
from 1.2 to 2.0 without redoing subscriptions for the subscribers.  Your best
bet, right now, is to drop 1.2 replication and create 2.0 replication.

I'll probably poke at this a bit over the holidays.


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