Nugent, Brian wrote:

>I need a replication system for PostgreSQL.  I have laptops that spend 4 to 5 days off of the network at a time.  Will slony1 work with a mobile work force?  
>
It can work, for certain values of "work."  :-)

You probably need to more precisely outline what you're intending to do;
I can foresee both scenarios that would function well, scenarios that
would function, albeit badly, as well as scenarios where things wouldn't
work out at all.

What do you intend for those "mobile users" to be able to access and
update on their "replication nodes"?

Note that with Slony-I, each replicated table can only have a single
origin.  Thus, if you want to have the laptops feed data back, each one
will need to be "master" of some of its own tables, which will feed back
to some central server that will have a process to consolidate those
updates.

Event propagation is almost certain to be troublesome if hosts are off
the network for days at a time.  That could cause problems that are a
bit difficult to predict.

I would urge prototyping it from the standpoint of seeing if it is
practical _at all_, as opposed to assuming that it'll work...  There's a
fair chance that it won't work out :-(.

>Also, what is the maximum object size that slony1 will handle?
>  
>
It won't handle BLOBs, if that's what you were thinking of using.

I'm not aware of any restrictions on the size of TEXT or BYTEA fields,
on the other hand, so if you plan to have perhaps-arbitrarily-large such
fields, that should work.

We are replicating an RT3 database which stores attachments in TEXT
fields; there is one more than 40MB in size, so it would appear that the
practical limit isn't lower than 40MB...