MySQL官方文档阅读二
What is New in MySQL 8.0
This section summarizes what has been added to,deprecated in 弃用,and removed from MySQL 8.0 。A companion 陪伴 section lists MySQl server options and variables that have added,deprecated,or removed in MySQL 8.0;see Section 1.4 "Server and Status Variables and Options Added,Deprecated,or Removed in MySQL8.-"
本章总结了MySQL8.0 版本中的新增，弃用，和移除的功能。下面的章节列出了8.0版本新增，弃用，和移除的选项和变量。
.Features Added in MySQL 8.0
.Features Deprecated in MySQL 8.0
.Features Removed in MySQL 8.0
Features Added in MySQL 8.0
The following features have been added to MySQL 8.0:
.Data dictionary. MySQL now incorporates 包含 a transactional data dictonary that stores information about database objects. In previous MySQL releases,dictionary data was stored in metadata files and nontransactional tables.For more information,see Chapter 14,MySQL Data Dictionary.
数据字典。MySQL 现在采用事务数据字典来存储数据库的对象信息。在之前的MySQL版本中，字段数据存放在元数据文件和非事务表中。更多信息参考14章节。
.Atomic data definition statements (Atomic DDL)。An atomic DDL statement combines联合，结合 the data dictionary updates,storage engine operations,and binary二进制 log writes associated 联系 with a DDL operation into a single 单一的,atomic transaction.
原子DDL语句，原子DDL语句把DDL语句关联的数据字典更新，存储引擎操作，和DDL操作产生二进制日志写入一个单一的原始的事务中。详见13.11章节。
.Upgrade procedure. Previously,after installation of a new version of MySQL,the MySQL server automatically upgrades the data dictionary tables at the next startup,after which the DBA is expected to invoke 借助 mysql_upgrade manually to upgrade the system tables in the mysql schema,as well as objects in other schemas such as the sys schema and user schemas.
更新程序，在之前的版本，在新安装MySQL后，在下次服务启动时，MySQL服务更新数据字典表，之后DBA应用mysql_upgrade手动更新mysql schema中的系统表，和其他模式中的对象，比如sys schema和use schemas。
As of MySQL 8.0.16,the server performs the tasks previously事先 handled 操作 by mysql_upgrade.After installiation of a new MySQL version,the server now automatically performs all necessary upgrade tasks at the next startup and is not dependent on the DBA invoking mysql_upgrade.In addition除此之外 ,the server updates the contents内容 of the help tables(something mysql_upgrade did not do).A new--upgrade server option provides control over how the server performs automatic data dictionary and server upgrade operations.For more information,see Section 2.11.3,"What the MySQL Upgrade Process Upgrades".
在8.0.6之前，服务器需要手动执行mysql_upgrade， 安装了新版本以后，在下一次启动前自动执行升级操作，不需要DBA手动执行。除此之外，服务器更新帮助表的内容，一个新的upgrade服务选项提供服务器服务器如何执行动态数据字典和更新选项的控制。
.Session Reuse.MySQL Server now supports SSL session reuse by default with a timeout setting to control how long the server maintains a session cache that establishes建立 the period 一段时间 during which a client is permitted to request session reuse for new connections.All MySQL client programs support session reuse.For server-side and client-side configuration informatino,see Section 6.3.5,"Reusing SSL Session"
In addition，C applications now can use the C API capabilities to enable session reuse for encrypted 加密 connections(see SSL Session Reuse).
MySQL现在支持SSL事务重用，并使用超时设置去控制 服务器维护回话缓存的时间，该缓存建立了允许客户端为新连接请求回话的时间段。 所有的客户端支持任务重用。服务端和客户端更多的配置信息参见6.3.5章节。
此外，C应用可以使用C API接口来为加密连接启用回话重用。
.Security and account management. These enhancements 增强 were added to improve security and enable greater大的DBA flexibility in account management:
安全和账户管理。以下增强的几点使DBA更安全和灵活的管理账户安全：
https://dev.mysql.com/doc/refman/8.0/en/mysql-nutshell.html
https://www.jianshu.com/p/a9fc55158260
