Horton

Re: Renaming of pg_xlog and pg_clog

Alvaro Herrera <alvherre@2ndquadrant.com>

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From: Alvaro Herrera <alvherre@2ndquadrant.com>
To: Bruce Momjian <bruce@momjian.us>
Cc: Greg Stark <stark@mit.edu>, Stephen Frost <sfrost@snowman.net>, Robert Haas <robertmhaas@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>, Christoph Berg <myon@debian.org>, Peter Eisentraut <peter.eisentraut@2ndquadrant.com>, Michael Paquier <michael.paquier@gmail.com>, Thomas Munro <thomas.munro@enterprisedb.com>, Craig Ringer <craig.ringer@2ndquadrant.com>, Jim Nasby <Jim.Nasby@bluetreble.com>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>, Andres Freund <andres@anarazel.de>
Date: 2016-10-24T14:59:42Z
Lists: pgsql-hackers 
Bruce Momjian wrote:
> On Sat, Oct 22, 2016 at 11:18:28PM +0300, Greg Stark wrote:

> > I think the apt-get behaviour was specifically designed to ensure it
> > couldn't easily be put into a script which I would have said was
> > desirable -- except I suspect there are situations where Postgres
> > database scripts need to do a resetxlog. I'm not sure I can think of
> > any examples offhand but I wouldn't be too surprised.
> 
> Yes, pg_upgrade has eight calls to pg_resetxlog to set various value.

There is one difference though, which is that the really destructive
use of pg_resetxlog is the one that removes pg_xlog files.  The other
uses that simply set flags in the control file are not as bad -- you can
simply go back to what the original value was.  I think we would only
need the obnoxious string requirement in the most dangerous mode.

Alternatively, we could separate the tool in two different executables.

-- 
Álvaro Herrera                https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

Commits

  1. Rename "pg_clog" directory to "pg_xact".

  2. Improve error reporting in pg_upgrade's file copying/linking/rewriting.