Re: BUG #15347: Unaccent for greek characters does not work

On Fri, Aug 24, 2018 at 2:07 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Thomas Munro <thomas.munro@enterprisedb.com> writes:
>> On Fri, Aug 24, 2018 at 12:12 PM, Michael Paquier <michael@paquier.xyz> wrote:
>>> Perhaps it would be better to avoid non-ASCII characters in this script?
>
>> You mean in the Python script?  Why?  At the top it has a PEP-263
>> encoding declaration:
>> # -*- coding: utf-8 -*-
>
> What happens if someone tries to view this in a non-UTF8 encoding?
>
> As a comparison point, we generally avoid using non-ASCII characters
> directly in the SGML docs; we write out the appropriate SGML entity
> instead.  I think we should try to do the equivalent thing here ---
> I assume python has some way to write "U+nnnn" or some such.

Ok, 2 against 1.  Done.

I'll wait for other opinions on what to do about lower case sigma
before committing.  I'm not keen on adding that special case because:

1.  It's a new kind of thing: previously we did only accent and
ligature removal, but this is removal of variants that exist in only
one case.  It's admittedly a bit like the German ß, which lacks an
upper case version according to some German speakers and undergoes a
lossy conversion to double-S, but that was already handled without a
special case by ligature expansion, so it's not the same thing.

2.  We are down to only 5 hardcoded special cases: two Cyrillic
characters which I suspect will go away if we allow Cyrillic to be
processed via the general mechanism as we are doing here with Greek,
and 3 oddballs that we inherited from the old hand-maintained
unaccent.rules files: DEGREE CELSIUS, DEGREE FAHRENHEIT, and SOUND
RECORDING COPYRIGHT.  I think the degrees signs can be done
automatically with just a bit more Unicode smarts, and I might try
reporting SOUND RECORDING COPYRIGHT as missing from
<character-fallback> to the CLDR project whose data we're using.

3.  The problem seems to go away by itself if you convert to upper case.

--
Thomas Munro
http://www.enterprisedb.com