Additional DB interface

[Bron Gondwana]

Hi All,

I'm seriously considering adding an interface to the Cyrus DB
abstraction.  It's basically "fetch_next" - which is like fetch,
but returns the alphabetically NEXT record rather than the given
key.  It already exists (pretty much) inside foreach, but I'd
like to have it outside.

Basically there are a couple of reasons - but the main one is to
be able to chunk things - for example duplicate_prune.  I just
watched a duplicate_prune for over 1/2 hour doing stacks of
fdatasync as it wrote every single delete.  I'd like to do a
few thousand records at a time.  The ideal (fastest!) way would
be to read a few thousand records under a single transaction,
commit all the deletes, then start again.  At the moment the
only interfaces are:

a) one transaction per record; or
b) one transaction for the entire file

There's no nice way to break it up into bite sized chunks!

What do you think?  Any suggestions about what you'd want or
what you might use?  Does this interface seem sane?

Regards,

Bron.