I'm sorry, did you have a bug to report?
This seems like an RFP.
There are a number of consulting firms that work with PostgreSQL that might
be prepared to submit material for an RFP, given a retainer or other
guarantee of payment.
Absent that, you might want to do some of your own research, perhaps
comparing material from the respective sets of documentation for the
various systems of interest to you on the basis of whatever sorts of
functionality matter to you and your clients. And actually, in order for
you to acquire the competent knowledge that you'd need to support those
clients, I wouldn't think there's any alternative to doing the research
inside your own organization.
--
When confronted by a difficult problem, solve it by reducing it to the
question, "How would the Lone Ranger handle this?"
