Handling incompatible API versions

[cmccoy]

We should decide how to structure code handling incompatible API changes for different database versions. I've seen:

• Backwards-incompatible API changes (e.g., HBase 0.9x to 1.x, see Add an HBase 1.0 client. #225).
• New APIs (e.g., Cassandra CQL, see rebased PR145: "Added Cassandra CQL binding" #270).

Currently we're including multiple clients within a single module, but I think it would be cleaner to have a separate module for incompatible versions. The HBase client, for example, now needs to be compiled against HBase 1.0.x. I think having an hbase-10 module and hbase-09 module might be better.

[busbey]

yes, definitely. in the case of HBase it should probably be hbase-94 and hbase-1.0 (and if the hbase-1.0 client doesn't work properly with a 0.98 cluster, we'll also need an hbase-98).

In addition to making the transition across versions clearer to downstream folks, this also makes it easier to deal with conflicting runtime needs.

[cmccoy]

This is done for HBase.

[risdenk]

Closing since this has been implemented with HBase and other bindings.