first level controlled by capacity, but not counter. second level controlled by counter

gistfile1.txt

testFallbackStartsAt = Some(2, 3)

val bitMaxCapacity = testFallbackStartsAt match {
  case Some(c1, _) => log2(c1)
  case _ => sqlContext.conf.fastHashAggregateRowMaxCapacityBit
}

// 1st level hash map
agg_buffer = fastHashMap.findOrInsert(key);

if (agg_buffer == null) {
  // generated. code for key in unsafe row format
  ...
  if (counter < 3) {
    // 2nd level hash map
    agg_buffer = regularHashMap.getAggregationBufferFromUnsafeRow(key_in_unsafe_row, ...);
  }
  if (agg_buffer == null) {
    // sort-based fallback
    regularHashMap.destructAndCreateExternalSorter();
    ...
    counter = 0;
  }
}
counter += 1;