Re: ALTER TABLE lock strength reduction patch is unsafe

From: Bruce Momjian <bruce(at)momjian(dot)us>
To: Heikki Linnakangas <hlinnakangas(at)vmware(dot)com>
Cc: Simon Riggs <simon(at)2ndQuadrant(dot)com>, Peter Geoghegan <pg(at)heroku(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Noah Misch <noah(at)leadboat(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: ALTER TABLE lock strength reduction patch is unsafe
Date: 2014-01-28 17:26:56
Message-ID: 20140128172656.GK20898@momjian.us
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On Tue, Jan 28, 2014 at 07:21:50PM +0200, Heikki Linnakangas wrote:
> >>I have no problem removing the parameter if required to. In that case,
> >>I would like to leave the parameter in until mid beta, to allow
> >>greater certainty. In any case, I would wish to retain as a minimum an
> >>extern bool variable allowing it to be turned off by C function if
> >>desired.
> >
> >Anything changed to postgresql.conf during beta is going to require an
> >initdb.
>
> Huh? Surely not.

Uh, if we ship beta1 with a GUC in postgresql.conf, and then we remove
support for the GUC in beta2, anyone starting a server initdb-ed with
beta1 is going to get an error and the server is not going to start:

LOG: unrecognized configuration parameter "xxx" in file "/u/pgsql/data/postgresql.conf" line 1
FATAL: configuration file "/u/pgsql/data/postgresql.conf" contains errors

so, yeah, it isn't going to require an initdb, but it is going to
require everyone to edit their postgresql.conf. My guess is a lot of
people are going to assume the old postgresql.conf is not compatible and
are going to initdb and reload.

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

+ Everyone has their own god. +

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