PostgreSQL 10.0 preview 变化 - pg_xlog,pg_clog,pg_log目录更名为pg_wal,pg_xact,log

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原文链接：https://yq.aliyun.com/articles/73933

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PostgreSQL 10.0 对部分目录进行了更名，包括将 pg_xlog 更名为 pg_wal，以避免用户误解这些目录内容的重要性。此外，还更改了默认的日志目录。

背景

10.0 把几个有一定“歧义”的目录更名了。它们分别为

pg_xlog, pg_clog, pg_log

更名为

pg_wal, pg_xact, log

分别对应WAL（write ahead log）日志，事务状态日志，日志。

省得有人误删其中的LOG目录中的文件。（还真有发生过）。

坏处是，如果有对应的程序用到了这几个目录名的，需要修改一下。

对应patch

Rename "pg_xlog" directory to "pg_wal".  
  
author	Robert Haas <rhaas@postgresql.org>	  
Thu, 20 Oct 2016 23:24:37 +0800 (11:24 -0400)  
committer	Robert Haas <rhaas@postgresql.org>	  
Thu, 20 Oct 2016 23:32:18 +0800 (11:32 -0400)  
"xlog" is not a particularly clear abbreviation for "write-ahead log",  
and it sometimes confuses users into believe that the contents of the  
"pg_xlog" directory are not critical data, leading to unpleasant  
consequences.  So, rename the directory to "pg_wal".  
  
This patch modifies pg_upgrade and pg_basebackup to understand both  
the old and new directory layouts; the former is necessary given the  
purpose of the tool, while the latter merely avoids an unnecessary  
backward-compatibility break.  
  
We may wish to consider renaming other programs, switches, and  
functions which still use the old "xlog" naming to also refer to  
"wal".  However, that's still under discussion, so let's do just this  
much for now.  
  
Discussion: CAB7nPqTeC-8+zux8_-4ZD46V7YPwooeFxgndfsq5Rg8ibLVm1A@mail.gmail.com  
  
Michael Paquier

Rename "pg_clog" directory to "pg_xact".  
  
author	Robert Haas <rhaas@postgresql.org>	  
Fri, 17 Mar 2017 21:46:58 +0800 (09:46 -0400)  
committer	Robert Haas <rhaas@postgresql.org>	  
Fri, 17 Mar 2017 21:48:38 +0800 (09:48 -0400)  
Names containing the letters "log" sometimes confuse users into  
believing that only non-critical data is present.  It is hoped  
this renaming will discourage ill-considered removals of transaction  
status data.  
  
Michael Paquier  
  
Discussion: http://postgr.es/m/CA+Tgmoa9xFQyjRZupbdEFuwUerFTvC6HjZq1ud6GYragGDFFgA@mail.gmail.com

Change default of log_directory to 'log'  
  
author	Peter Eisentraut <peter_e@gmx.net>	  
Mon, 27 Mar 2017 22:34:33 +0800 (10:34 -0400)  
committer	Peter Eisentraut <peter_e@gmx.net>	  
Mon, 27 Mar 2017 22:34:33 +0800 (10:34 -0400)  
The previous default 'pg_log' might have indicated by its "pg_" prefix  
that it is an internal system directory.  The new default is more in  
line with the typical naming of directories with user-facing log files.  
Together with the renaming of pg_clog and pg_xlog, this should clear up  
that difference.  
  
Author: Andreas Karlsson <andreas@proxel.se>

这个patch的讨论，详见邮件组，本文末尾URL。

PostgreSQL社区的作风非常严谨，一个patch可能在邮件组中讨论几个月甚至几年，根据大家的意见反复的修正，patch合并到master已经非常成熟，所以PostgreSQL的稳定性也是远近闻名的。