Jim Archer wrote:

>Hi All...
>
>Over the weekend, I was playing with Slony.  I noticed that if I try to
>modify a data table on a slave node I get an error, which is good.  I also
>noticed, however, that I can call nextval() against a sequence and get the
>next value.
>
>Afte doing this I added a record to the master, which populated a column
>with the next sequence value, and the record replicated with the value
>from the master.
>
>I am guessing when I reconfigure the cluster do the slave becomes the
>origin that the sequence will pick up at its value after my call to
>nextval(), but I am also thinking this is harmless, unless there is an
>issue with my code.  Is this all correct?
>  
>
What you'll see on a subscriber node is that the current value of the
sequence will be regularly reset to the then-present value on the origin
node.

I suppose that if you ran nextval()/setval() on the subscriber at the
wrong time, you could "muss things up" somewhat by forcing a value
inconsistent with what you had elsewhere.

But as long as you've not got processes that are cavalier about updating
sequences, the subscriber should often enough get reset to the state on
the origin, and when the origin shifts to the subscriber, the subscriber
can be expected to have the right value for the sequence to pick up and
move on...

It's probably always possible to shoot yourself in the foot; keep those
misplaced nextval()s to a "dull roar" and you should be OK :-).