#16 abstraction for bulk updates: versionedmapping? updatecomman

[Alan Knight]

It would be nice to have a mechanism for dealing with bulk
updates that didn't require reading all the objects into
memory. Similarly, bulk inserts, where you can do an
INSERT ... SELECT WHERE to copy (a subset of) rows.

However, integrating this with the other functionality is
tricky. Where in the sequence of unit of work operations
should this happen. How would it interact with other things
that affect that relationship.

One option would be to create mappings that know how to
deal with particular special cases where this is useful. For
example, a VersionedMapping that can do this in a
disciplined way. Does this mean that somewhere in therer
there's an Updatecommand?