PostgreSQL 9.3 Make the streaming replication protocol messages architecture-independent

Allow tools like pg_receivexlog to run on computers with different architectures (Heikki Linnakangas)
WAL files can still only be replayed on servers with the same architecture as the primary; but they can now be transmitted to and stored on machines of any architecture, since the streaming replication protocol is now machine-independent.

Make the streaming replication protocol messages architecture-independent.
We used to send structs wrapped in CopyData messages, which works as long as
the client and server agree on things like endianess, timestamp format and
alignment. That's good enough for running a standby server, which has to run
on the same platform anyway, but it's useful for tools like pg_receivexlog
to work across platforms.

This breaks protocol compatibility of streaming replication, but we never
promised that to be compatible across versions, anyway.

PostgreSQL 9.3 对流复制协议的改进之一, 跨平台兼容.

例如你的数据库跑在x86主机上, 同时你可以在IBM小型机上使用同一版本的数据库软件(例如pg_receivexlog工具.)通过流复制协议接收x86主机上的xlog文件.

[参考]

1. http://git.postgresql.org/gitweb/?p=postgresql.git;a=commit;h=add6c3179a4d4fa3e62dd3e86a00f23303336bac

2. http://www.postgresql.org/docs/devel/static/app-pgreceivexlog.html