private void checkClosedRegions(MasterProcedureEnv env) throws IOException {
    // theoretically this should not happen any more after we use TRSP, but anyway let's add a check
    // here
    AssignmentManagerUtil.checkClosedRegion(env, getParentRegion());
  }
Calculate daughter regionid to use.
@param hri Parent {@link RegionInfo}
@return Daughter region id (timestamp) to use.
hbase-server/src/main/java/org/apache/hadoop/hbase/master/assignment/SplitTableRegionProcedure.java