protected boolean includeRegionInSplit(final byte[] startKey, final byte[] endKey) {
    return true;
  }
Test if the given region is to be included in the InputSplit while splitting the regions of a
table.
<p>
This optimization is effective when there is a specific reasoning to exclude an entire region
from the M-R job, (and hence, not contributing to the InputSplit), given the start and end keys
of the same. <br>
Useful when we need to remember the last-processed top record and revisit the [last, current)
interval for M-R processing, continuously. In addition to reducing InputSplits, reduces the
load on the region server as well, due to the ordering of the keys. <br>
<br>
Note: It is possible that <code>endKey.length() == 0 </code> , for the last (recent) region.
<br>
Override this method, if you want to bulk exclude regions altogether from M-R. By default, no
region is excluded( i.e. all regions are included).
@param startKey Start key of the region
@param endKey   End key of the region
@return true, if this region needs to be included as part of the input (default).
hbase-mapreduce/src/main/java/org/apache/hadoop/hbase/mapreduce/TableInputFormatBase.java