Re: pgsql: doc: mention dependency on collation libraries

On Thu, Jul 21, 2016 at 09:59:42AM +0200, Christoph Berg wrote:
> Re: Bruce Momjian 2016-07-20 <20160720161318(dot)GE24559(at)momjian(dot)us>
> > > > How about simply this: ?
> > > >
> > > > Non<literal>C</> and and non-<literal>POSIX</> locales rely on the
> > > > operating system's collation library for character set ordering.
> > > > This controls the ordering of keys stored in indexes. For this
> > > > eason,
> > > > a cluster cannot switch to an incompatible collation library
> > > > ersion,
> > > > either through
> > > >
> > > > + operating system upgrade,
> > > >
> > > > snapshot restore, binary streaming replication, or
> > > > <application>pg_upgrade</> run.
> > >
> > > OK, good point. I was more focused on cluster moves than an OS change.
> > > How is the attached patch?
> >
> > With the mention of different operating systems, there is no need to
> > mention pg_upgrade anymore as it is already covered. Updated patch
> > attached.
>
> With that argument, you could drop snapshot restore and replication as
> well, as "different OS (version)" is the real problem. Still,
> mentioning pg_upgrade would highlight the fact that it doesn't "fix"
> the problem in the same sense that pg_dump would. Collation changes
> are subtle changes that are surprising in many cases, so mention a few
> cases makes people aware more.

I mentioned snapshot restore and replication as a way to highlight that
it is binary transfer that is the problem, not pg_dump.

You are right about pg_upgrade not fixing the problem, but since it only
runs on the same machine, I don't see it as a good example.

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

+ As you are, so once was I. As I am, so you will be. +
+ Ancient Roman grave inscription +