PostgreSQL10.0preview變化-pg_xlog,pg_clog,pg_log目錄更名為pg_wal,pg_xact,log

標籤

PostgreSQL , 10.0 , pg_xact , pg_wal , log , pg_clog , pg_xlog , pg_log

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背景

10.0 把幾個有一定“歧義”的目錄更名了。它們分別為

pg_xlog, pg_clog, pg_log

更名為

pg_wal, pg_xact, log

分別對應WAL（write ahead log）日誌，事務狀態日誌，日誌。

省得有人誤刪其中的LOG目錄中的檔案。（還真有發生過）。

壞處是，如果有對應的程式用到了這幾個目錄名的，需要修改一下。

對應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>  

這個patch的討論，詳見郵件組，本文末尾URL。

PostgreSQL社群的作風非常嚴謹，一個patch可能在郵件組中討論幾個月甚至幾年，根據大家的意見反覆的修正，patch合併到master已經非常成熟，所以PostgreSQL的穩定性也是遠近聞名的。

參考

https://git.postgresql.org/gitweb/?p=postgresql.git;a=commitdiff;h=f82ec32ac30ae7e3ec7c84067192535b2ff8ec0e

https://git.postgresql.org/gitweb/?p=postgresql.git;a=commitdiff;h=88e66d193fbaf756b3cc9bf94cad116aacbb355b

https://git.postgresql.org/gitweb/?p=postgresql.git;a=commitdiff;h=3371e4d9b12455fe1f8d1516d0bd915aab86be17