Feature Request: Expiration per Bucket (Not per backend)

[alexmoore]

Moved from basho/bitcask#94

Customer needs support for more than a handful of different expiration settings. They would like support for dozens to <100 of different expiration settings without configuring backends for each of them, hence the support by bucket.

Some brainstorming brought up the possibility of attaching an expiry date timestamp next to the creation timestamp in the bitcask entry or as metadata, but Evan quickly shot this down. Implementation details aside, it would be a very nice feature.

From ZD:4865

At any rate, we do currently map buckets to specific multi-backends that have different expiration settings, but we have product requests to do more expiration options than the handful, 7 or 60 days that we currently offer. We don't want to get into a cycle of adding new backend configurations to app.config.

...Breaking those datasets further by a variety of retention policies would cause a multiplication of backends that Riak is not currently built to handle. (dozens, if not more than a hundred)