XFER when changing database formats

[Wesley Craig]

On 28 Oct 2009, at 09:43, David Mayo wrote:
> I am now looking at transferring our users to the new back-end server.
> The XFER command seems to do the job perfectly, except for the seen  
> and
> subscription databases because we are changing formats from flat to  
> skplist.

> Looking at the telemetry, it appears the XFER command just dumps
> everything raw and the other end slurps it in without  
> interpretation. We
> get lots of errors in the logs[1] and unfortunately the sync client
> doesn't take too kindly to this either, and bails out!

That's correct.

> Our users won't accept losing their seen state. I can convert the seen
> state before/after the XFER with a bit of work, however does anyone  
> knew
> of a cleaner solution that saves me having to run two different  
> processes?

I'm not aware of an off-the-shelf solution.  It might be possible for  
undump_mailbox() to examine the xfer'd data and convert it before  
instantiating it.  flat doesn't have a magic number, but skiplist  
does.  Presumably BDB does too, tho Cyrus doesn't know about it  
directly.  A general solution would probably be hard and/or ugly.

If it were me, I'd probably keep the file formats the same until XFER  
is complete and convert after the fact.

:wes