Support Filters for Get and Scan requests.

[ishan]

Official client API supports adding "Filters" to get and scan requests, which is useful pushing down qualifier selection logic to Hbase.

Just wanted to get a sense from you on how much effort would be required in adding this.

[jasonculverhouse]

I've done some testing on this in our branch of asynchbase (which has diverged quite a bit from this one) the changes are not too difficult. I'd like to sync our version back up with the official version when I have some time.

Here is a commit that adds filter support to the get request (I didn't implement the scan)
Flipboard@2825587

import org.apache.hadoop.hbase.util.Writables;
import org.apache.hadoop.hbase.filter.ColumnPaginationFilter;

GetRequest = new GetRequest(...);
ColumnPaginationFilter filter = new ColumnPaginationFilter(200, 0);
getreq.filterName(filter.getClass().getName().getBytes());
getreq.filter(Writables.getBytes(filter));

[tsuna]

This issue relates in part to #51 (for the scanner part).

[jasonculverhouse]

Yes, these two things are the same, if you were to use something like "HBaseRpc.HasFilter" and just pass the name and the filter bytes then the filter mechanism remains pretty opaque. There are cases where you need to build a filter list and just one column based filter isn't going to be enough.

The existing scanner filter could be made compatible with this more generic mechanism.

[tsuna]

Yup, we're adding a number of filters (see pull request #56 which I've integrated in my repo for the scan filter part). We could add that interface to tack on a filter on HBaseRpc subclasses that can use a filter.