@Override
  protected Pair<byte[][], byte[][]> getStartEndKeys() throws IOException {
    if (conf.get(SPLIT_TABLE) != null) {
      TableName splitTableName = TableName.valueOf(conf.get(SPLIT_TABLE));
      try (Connection conn = ConnectionFactory.createConnection(getConf())) {
        try (RegionLocator rl = conn.getRegionLocator(splitTableName)) {
          return rl.getStartEndKeys();
        }
      }
    }

    return super.getStartEndKeys();
  }
Convenience method to parse a string representation of an array of column specifiers.
@param scan    The Scan to update.
@param columns The columns to parse.
hbase-mapreduce/src/main/java/org/apache/hadoop/hbase/mapreduce/TableInputFormat.java