message: support multiple compression algorithm
diff: @@ -67,8 +67,13 @@ PikaServer::PikaServer() :
  option.max_open_files = g_pika_conf->max_cache_files();
  option.max_bytes_for_level_multiplier = g_pika_conf->max_bytes_for_level_multiplier();
  if (g_pika_conf->compression() == "none") {
  - option.compression = false;
  + option.compression = nemo::Options::CompressionType::kNoCompression;
  + } else if (g_pika_conf->compression() == "snappy") {
  + option.compression = nemo::Options::CompressionType::kSnappyCompression;
  + } else if (g_pika_conf->compression() == "zlib") {
  + option.compression = nemo::Options::CompressionType::kZlibCompression;
  }
  +
  std::string db_path = g_pika_conf->db_path();
  LOG(INFO) << "Prepare DB...";
  db_ = std::shared_ptr<nemo::Nemo>(new nemo::Nemo(db_path, option));
  @@ -393,7 +398,11 @@ bool PikaServer::ChangeDb(const std::string& new_path) {
  option.max_open_files = g_pika_conf->max_cache_files();
  option.max_bytes_for_level_multiplier = g_pika_conf->max_bytes_for_level_multiplier();
  if (g_pika_conf->compression() == "none") {
  - option.compression = false;
  + option.compression = nemo::Options::CompressionType::kNoCompression;
  + } else if (g_pika_conf->compression() == "snappy") {
  + option.compression = nemo::Options::CompressionType::kSnappyCompression;
  + } else if (g_pika_conf->compression() == "zlib") {
  + option.compression = nemo::Options::CompressionType::kZlibCompression;
  }
  std::string db_path = g_pika_conf->db_path();
  std::string tmp_path(db_path);
  @@ -1395,8 +1404,13 @@ bool PikaServer::FlushAll() {
  option.max_open_files = g_pika_conf->max_cache_files();
  option.max_bytes_for_level_multiplier = g_pika_conf->max_bytes_for_level_multiplier();
  if (g_pika_conf->compression() == "none") {
  - option.compression = false;
  + option.compression = nemo::Options::CompressionType::kNoCompression;
  + } else if (g_pika_conf->compression() == "snappy") {
  + option.compression = nemo::Options::CompressionType::kSnappyCompression;
  + } else if (g_pika_conf->compression() == "zlib") {
  + option.compression = nemo::Options::CompressionType::kZlibCompression;
  }
  +
  LOG(INFO) << "Prepare open new db...";
  db_ = std::shared_ptr<nemo::Nemo>(new nemo::Nemo(g_pika_conf->db_path(), option));
  LOG(INFO) << "open new db success";
  