private void ensureAliasFilter() throws HiveException {
    if (!isAliasFilterSet && rowLength > 0) {
      for (int offset = rowLength - 1; offset < array.length; offset += rowLength) {
        aliasFilter &= ((ShortWritable)array[offset]).get();
      }
    }
    isAliasFilterSet = true;
  }
Row iterator for non-zero-length rows.
ql/src/java/org/apache/hadoop/hive/ql/exec/persistence/FlatRowContainer.java