2.19.05.0 版本 DBLE Release Notes
以下对 DBLE 2.19.05.0 版本的 Release Notes 进行详细解读。
文章主要分为五部分内容：
一、DBLE 项目介绍
二、更新概况
三、新特性
四、升级兼容性
五、DBLE Release Notes
一、DBLE 项目介绍
DBLE 是企业级开源分布式中间件，江湖人送外号 “MyCat Plus”；以其简单稳定，持续维护，良好的社区环境和广大的群众基础得到了社区的大力支持。
DBLE 官方项目：
https://github.com/actiontech/dble
如对源码有兴趣或者需要定制的功能的可以通过源码编译安装。
DBLE 官方文档：
https://actiontech.github.io/dble-docs-cn
可以详细了解 DBLE 的背景和应用场景，本文未涉及到的细节都可在官方文档获得。
DBLE 下载地址：
https://github.com/actiontech/dble/releases
[点击学习 DBLE 公开课，Mycat 用户更快上手哦！]
Tips：建议下载最新的 Releases 版本，下载 tar 压缩包即可，如有源码编译需求的，可以下载源码包。
二、版本概况
距上一次 4 月 22 日【发版（2.19.03.0）】已有两个多月，DBLE 社区又迎来了新版本的更新。
最新的 Release Notes 请参考：
https://github.com/actiontech/dble/releases
新增 7 个特性，修复了 36 缺陷；
//划重点
感谢 Github 用户提供的优质 issue ，还有 QQ 群提供的有效反馈的朋友
issue 反馈质量不断提高，保证了快速响应修复
发版频率在稳定后会降低到两个月一次
三、新特性
本次重点功能更新主要增加如下几点：
支持 MySQL 8.0（alpha特性）
对存储过程 hint 的完整支持 支持自定义告警接口（alpha特性）
优化最大连接数的默认值修改方式
更便捷的配置模板
四、升级兼容性
新版 DBLE 完全兼容以往功能。
这次的更新离不开 DBLE 社区爱好者们的热情支持，是你们的试用实践使得 DBLE 功能越加稳定和成熟。
未来 DBLE 社区将继续积极地推动 DBLE 的开源，让更多的 MySQL 用户能够使用到免费好用的分布式中间件。
五、DBLE Release Notes
Features:
Change the default max size of frontend connection for each user #1218
Support MySQL8.0's default authentication plugin named 'caching_sha2_password' #1134
Split Origin Merge to Merge And MERGE_AND_ORDER for Explain Plan #1139
Optimize global sequence generated by distributed timestamp #1138
Improve dble's config template #1078
The error messages should be more meaningful when dble instances are doing DDL simultaneously in one cluster #1105
Support Stored procedure when connection enabled multiple statements
Define alarm interface for developers to customize
Bug-fixes:
An error occurred while using Alibaba Cloud slb load balancing #1172
Unknown pStmtId error when closing a prepared-statement that statement is the same as another in one connection #1236
Backend conns will be closed when executing 'log @@limit=0,5000' in dble managed port #1220
The network interrupt between dble and MySQL node before XA commit, the transaction lock in MySQL will always exist #1084
Load data incorrect when the text contains a row with all null columns #1047
SqlJob may finish more than once, and cause other problem #1231
FetchStoreNodeOfChildTableHandler can cause serverConnection hang & leak of MySQL connection #1180
NPE when using global sequence generated by MySQL-offset-step #1227
MultiNodeQueryHandler#errorResponse add only one connection to errConnection list #1166, thanks @tankilo
DateNode Idle Check Thread failed to fill empty dataSource when dataHost's minCon is less than database size, thanks @tankilo
When MultiNodeQueryHandler send multiple SQL statements to MySQL, if the middle part failed to execute, frontend session will hang #1164, thanks @tankilo
When complex cross join contained in an XA-transaction, the statement commit can't return #1116, thanks @kaikai2000
multinode statement hang when setting statement error before executing
Fail to recover XA Transaction on startup when XA log is not flushed and the server is down #1192
Xa transaction commit failed due to network exception and could not be recovered by restarting dble #1113
Even if the transaction is successfully restored, the state of the XA transaction in XA-log will always fail #1213
Sending a statement to an uncreated physical database can cause thread safety problem #1144
dble hang while inserting values into sharding table after executing "lock tables ... write" #1203
For sharding tables(the two tables have the ER relationship), now "left join" got the result from only one dataNode #1197
Load data will cause an exception when the column content only has one '"' at the beginning #1182, thanks @ssxlulu
When implicit XA transaction fails to commit and is automatically rollbacked, the real error should be returned to the user instead of OK packet #1170, thanks @tankilo
`Load data` execution result error when the load data file is empty #1198
XA Transaction failed to commit due to the previous one's remaining error message((XACommitNodesHandler)MultiNodeHandler#isFailed) #1156, thanks @tankilo
DDL lock can't be released when the server connection is abnormally closed #1168
when running Sysbench OLTP test, XA transaction can't restore correctly after restarting dble #1114, thanks @kaikai2000
It is recommended that `ZK` allow both uppercase and lowercase in the file of sequence_distributed_conf.properties #1162
if where filter‘s length of complex query lager than 255, dble may return error #1120
load data for a table using global sequence can not generate sequence column #1048
Global sequence error when generated by distributed timestamps #1153
show @@binlog.status query failed if all logic databases corresponding physical one's not created #1088
Some of the SQL Method params in a complex query must be uppercase #1132
Need to optimize, when starting dble, the configuration does not include the tables involved in the view #1100
SQL returns an error, after the MySQL node disconnects during DDL execution #1119
`Select query` to get results from multiple nodes may lead to thread safety problem #1147
Error when ` select * from sharding_2_t1 a right join sharding_4_t1 b on a.id=b.ID where a.id >0 and a.id <4` #1142
manager cmd "create database" error when connecting to dble with JDBC #1245
查看完整的 DBLE Release Notes
