/// <summary>
 /// 构造函数。
 /// </summary>
 /// <param name="tableName">表的名称</param>
 /// <param name="primaryKey"> 要删除的行的主键</param>
 public RowDeleteChange(String tableName, PrimaryKey primaryKey) : base(tableName, primaryKey)
 {
 }
 public RowUpdateChange(String tableName, PrimaryKey primaryKey, long ts) : base(tableName, primaryKey)
 {
     this.timestamp = ts;
 }