code: @Deprecated
    public void addPrimaryKey(String... primaryKeyFieldName) {
      StringBuilder sb = new StringBuilder(getProp(ConfigurationKeys.EXTRACT_PRIMARY_KEY_FIELDS_KEY, ""));
      Joiner.on(",").appendTo(sb, primaryKeyFieldName);
      setProp(ConfigurationKeys.EXTRACT_PRIMARY_KEY_FIELDS_KEY, sb.toString());
    }
docs: Add more primary keys to the existing set of primary keys.
  
  @param primaryKeyFieldName primary key names
  @deprecated @deprecated It is recommended to add primary keys in {@code WorkUnit} instead of {@code Extract}.