Re: Order changes in PG16 since ICU introduction

On Fri, 2023-04-21 at 20:12 -0400, Robert Haas wrote:
> On Fri, Apr 21, 2023 at 5:56 PM Jeff Davis <pgsql(at)j-davis(dot)com> wrote:
> > Most of the complaints seem to be complaints about v15 as well, and
> > while those complaints may be a reason to not make ICU the default,
> > they are also an argument that we should continue to learn and try
> > to
> > fix those issues because they exist in an already-released version.
> > Leaving it the default for now will help us fix those issues rather
> > than hide them.
> >
> > It's still early, so we have plenty of time to revert the initdb
> > default if we need to.
>
> That's fair enough, but I really think it's important that some
> energy
> get invested in providing adequate documentation for this stuff. Just
> patching the code is not enough.

Attached a significant documentation patch.

I tried to make it comprehensive without trying to be exhaustive, and I
separated the explanation of language tags from what collation settings
you can include in a language tag, so hopefully that's more clear.

I added quite a few examples spread throughout the various sections,
and I preserved the existing examples at the end. I also left all of
the external links at the bottom for those interested enough to go
beyond what's there.

I didn't add additional documentation for ICU rules. There are so many
options for collations that it's hard for me to think of realistic
examples to specify the rules directly, unless someone wants to invent
a new language. Perhaps useful if working with an interesting text file
format with special treatment for delimiters?

I asked the question about rules here:

https://www.postgresql.org/message-id/e861ac4fdae9f9f5ce2a938a37bcb5e083f0f489.camel%40cybertec.at

and got some limited response about addressing sort complaints. That
sounds reasonable, but a lot of that can also be handled just by
specifying the right collation settings. Someone who understands the
use case better could add some more documentation.

--
Jeff Davis
PostgreSQL Contributor Team - AWS