Re: Why do we let CREATE DATABASE reassign encoding?

I wrote:
> Peter Eisentraut <peter_e(at)gmx(dot)net> writes:
>> AFAIR, the only reason that we haven't disallowed this sort of stuff
>> years and years ago is that people use it; the Japanese in particular.
>> I don't see what is different now.

> What's different now is that 8.4 has already established the principle
> that you have to clone template0 if you want to change the locale of a
> database. I think this is a good time to establish the same principle
> for encodings. (Or in other words, if we don't fix it now, when will
> be a better time?)

Attached is a proposed patch (without documentation changes as yet)
for this. Since the code is already enforcing exact locale match when
cloning a non-template0 database, I just made it act the same for
encoding, without any strange exceptions for SQL_ASCII.

I found that mbregress.sh was already broken by the existing
restrictions, if you try to use it in a database whose default
locale isn't C. The patch adds switches to fix that.

The patch also incidentally fixes a few ereport's that were missing
errcode values.

Last chance for objections ...

regards, tom lane