Re: pgsql: doc: mention dependency on collation libraries

On Sat, Jul  2, 2016 at 06:02:12PM +0200, Christoph Berg wrote:
> Re: Bruce Momjian 2016-07-02 <20160702155517.GD18610@momjian.us>
> > > Shouldn't this mention that OS upgrades are a possible problem as
> > > well? We've seen the de_DE.UTF-8 ordering break in RHEL 5->6, and
> > > again in 6->7. (5 and 7 are compatible.) The problematic strings were
> > > "999" and "9-9-9".
> >
> > Yes, we can do that.  Do you have suggested wording?  I was not sure how
> > to tell people anything related to collation versions.
>
> 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?

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  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

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