Preformance issue on thrift API

while (curRow < maxRows && iter.hasNext) {
  val sparkRow = iter.next()
  val row = ArrayBuffer[Any]()
  var curCol = 0
  while (curCol < sparkRow.length) {
    if (sparkRow.isNullAt(curCol)) {
      row += null
    } else {
      addNonNullColumnValue(sparkRow, row, curCol, timeFormatters)
    }
    curCol += 1
  }
  resultRowSet.addRow(row.toArray.asInstanceOf[Array[Object]])
  curRow += 1
}

...
 while (i < rowSize) {
          val row = rows(I)
          ...