@Override
  protected byte[] getSplitPoint() {
    byte[] splitPoint = super.getSplitPoint();
    if (prefixLength > 0 && splitPoint != null && splitPoint.length > 0) {
      // group split keys by a prefix
      return Arrays.copyOf(splitPoint, Math.min(prefixLength, splitPoint.length));
    } else {
      return splitPoint;
    }
  }
A custom RegionSplitPolicy implementing a SplitPolicy that groups rows by a prefix of the row-key
This ensures that a region is not split "inside" a prefix of a row key. I.e. rows can be
co-located in a region by their prefix.
@deprecated since 3.0.0 and will be removed in 4.0.0. Use {@link RegionSplitRestriction},
            instead.
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/KeyPrefixRegionSplitPolicy.java