Ceph

A way to implement this is to enhance the pg_ls_repsonse_t to include the namespace (or change object_t to hobject_t). We'd have to provide a wildcard value (e.g. *, ALL) for the namespace to list all object in all namespaces.

A new librados list namespaces operation could run through the pg_ls_response_t for all objects and build a list of unique namespace names. Then a new rados command could be added to list namespaces for a given pool.

We could then easily add the long sought feature of a rados command that lists all objects in a pool in "namespace/objectname" format.

Finally, a printable wildcard value should be an illegal namespace name. Or a non-printable wildcard value would require an additional option to the rados command (e.g. --all, --all-namespaces).