Reversed scanners?

[wbolster]

The TScan struct in the Thrift definition has a reversed field in newer HBase versions.

[Tachyon5]

I would love love to see reversed method in the happybase api. Any development on this?

[wbolster]

Sorry, no code yet. I don't use HappyBase myself anymore, but still maintain it in my spare time because of my beloved users. ;-)

Anyway, to get support for this in HappyBase, the following needs to be known/done:

• Exact HBase version when the TScan.reversed field was introduced in the Thrift API
• A new reversed= arg to Table.scan() that should raise an exception in case it's enabled and the HBase version is too old.
• The exact behaviour in case the reversed field is set to true needs to be figured out, and I'm not sure this is properly documented/spec'ed, so I guess some experimentation is in order here:
  • does it swap start/stop arguments?
  • how can we still support the row_prefix= argument, which is currently implemented using a client-side (Python side) util.str_increment() helper that calculates the boundaries to be put in TScan.startRow and TScan.stopRow fields of the Thrift API.
• Of course all of this would need tests. Not extensive ones that check all possible combinations (other tests already do that), just a few that check the boundaries (e.g. start/stop key exclusive/inclusive? does limit work properly? does row_prefix= work properly?)

[Tachyon5]

If i can commit my group to upgrade to the newer version of HBase and Thrift , I will take a shot and implementing this. Thanks for the response.

[wbolster]

fixed by #155