message: change MAX_KEY_NUM to  1 << 31
diff: @@ -19,7 +19,7 @@ class ISArray
  {
  private:
  // stores at most 1 billion keys
  - static const unsigned int MAX_KEY_NUM = 300000000;
  + static const unsigned int MAX_KEY_NUM = 1 << 31;
  static const unsigned int SET_KEY_NUM = 10 * 1000 * 1000; // minimum initial keys num, same as RDFParser::TRIPLE_NUM_PER_GROUP
  static const unsigned int SET_KEY_INC = SET_KEY_NUM; // minimum keys num inc
  static const unsigned int SEG_LEN = 1 << 8;
  