Generating article numbers in new backends

[pedro . alex . silva]

Hello,

I'm writing a backend in which articles come in with SQL ids. These are
monotonic, and unique even over groups.  My understanding is that this
is suitable, but breaks some things. For example, upon implementing
`nnmybackend-request-list', I noticed that the active file format that
this function produces makes Gnus incorrrectly guess the number of
articles in every group.

Is the above harmless and can I just use these SQL IDs for article
numbers? If not, what is the best practice for generating Gnus-specific
article numbers? I've not been able to find documentation on any helper
functions for this. I perused nnimap and nnrss's source, but it's been
of no help.

Must I keep a local mapping of SQL IDs to Gnus article numbers? Can I
use the registry for that purpose?

Thanks,
-- 
Pedro

PS: I'm having problems with posting via eternal-september and email, so I'm 
trying Google Groups this time. Apologies in case of multiple postings.