PostgreSQL 9.4.4, 9.3.9, 9.2.13, 9.1.18 & 9.0.22 发布
PostgreSQL是以加州大学伯克利分校计算机系开发的 POSTGRES，现在已经更名为PostgreSQL，版本 4.2为基础的对象关系型数据库管理系统（ORDBMS）。PostgreSQL支持大部分 SQL标准并且提供了许多其他现代特性：复杂查询、外键、触发器、视图、事务完整性、MVCC。同样，PostgreSQL 可以用许多方法扩展，比如， 通过增加新的数据类型、函数、操作符、聚集函数、索引。免费使用、修改、和分发 PostgreSQL，不管是私用、商用、还是学术研究使用。
PostgreSQL主要优势：
1. PostgreSQL完全免费，而且是BSD协议，如果你把PostgreSQL改一改，然后再拿去卖钱，也没有人管你，这一点很重要，这表明了 PostgreSQL数据库不会被其它公司控制。oracle数据库不用说了，是商业数据库，不开放。而MySQL数据库虽然是开源的，但现在随着SUN 被oracle公司收购，现在基本上被oracle公司控制，其实在SUN被收购之前，MySQL中最重要的InnoDB引擎也是被oracle公司控制 的，而在MySQL中很多重要的数据都是放在InnoDB引擎中的，反正我们公司都是这样的。所以如果MySQL的市场范围与oracle数据库的市场范 围冲突时，oracle公司必定会牺牲MySQL，这是毫无疑问的。
2. 与PostgreSQl配合的开源软件很多，有很多分布式集群软件，如pgpool、pgcluster、slony、plploxy等等，很容易做读写分离、负载均衡、数据水平拆分等方案，而这在MySQL下则比较困难。
3. PostgreSQL源代码写的很清晰，易读性比MySQL强太多了，怀疑MySQL的源代码被混淆过。所以很多公司都是基本PostgreSQL做二次开发的。
4. PostgreSQL在很多方面都比MySQL强，如复杂SQL的执行、存储过程、触发器、索引。同时PostgreSQL是多进程的，而MySQL是线 程的，虽然并发不高时，MySQL处理速度快，但当并发高的时候，对于现在多核的单台机器上，MySQL的总体处理性能不如PostgreSQL，原因是 MySQL的线程无法充分利用CPU的能力。
PostgreSQL 9.4.4, 9.3.9, 9.2.13, 9.1.18 & 9.0.22 发布，这些版本主要是一些 bug 修复，建议用户更新。
The PostgreSQL Global Development Group has released an update to all supported versions of our database system, including 9.4.4, 9.3.9, 9.2.13, 9.1.18 and 9.0.22. This release primarily fixes issues not successfully fixed in prior releases. It should be applied as soon as possible all users of major versions 9.3 and 9.4. Other users should apply at the next available downtime.
Crash Recovery Fixes
Earlier update releases attempted to fix an issue in PostgreSQL 9.3 and 9.4 with "multixact wraparound", but failed to account for issues doing multixact cleanup during crash recovery. This could cause servers to be unable to restart after a crash. As such, all users of 9.3 and 9.4 should apply this update as soon as possible.
Servers previously upgraded to PostgreSQL 9.3 using pg_upgrade, even those servers now running PostgreSQL 9.4 due to another upgrade, may experience an immediate autovacuum of all tables after applying this update. For large databases, consider a controlled manual VACUUM, before updating, to better regulate the performance consequences of this critical maintenance. Please see the release notes for details.
Other Fixes and Improvements
In addition to the above, a few other minor issues were patched in this release. These fixes include:
- Prevent failure to invalidate relation cache init file
- Avoid deadlock between new sessions and CREATE/DROP DATABASE
- Improve query planning for semi-joins and anti-joins
Cumulative Releases
All PostgreSQL update releases are cumulative. As this update release fixes a number of problems inadvertently introduced by fixes in earlier update releases, we strongly urge users to apply this update, rather than installing less recent updates that have known issues. As this update release closes multiple known bugs with multixact handling, the PostgreSQL Project does not anticipate additional update releases soon.
Updating
As with other minor releases, users are not required to dump and reload their database or use pg_upgrade in order to apply this update release; you may simply shut down PostgreSQL and update its binaries. Users who have skipped multiple update releases may need to perform additional post-update steps; see the Release Notes for details. See also the above note for users who used pg_upgrade with PostgreSQL version 9.3.
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