Re: pgsql: doc: mention dependency on collation libraries

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.

Christoph