ADQL-2.1 internal draft

[Walter Landry]

Marco Molinaro <molinaro at oats.inaf.it> wrote:
> 2015-06-11 0:05 GMT+02:00 Walter Landry <wlandry at caltech.edu>:
>> I am not suggesting removing the 2.0 version with a coordinate system.
>> I am suggesting adding an overload and not having an implicit meaning
>> for an empty string.  That would retain the property of the current
>> proposal that all 2.0 queries are valid in 2.1, but not all 2.1
>> queries are valid in 2.0.
> 
> but while function overload is managed by postgresql, it's not in
> MySQL -e.g.-.

The guy down the hall from me who hacks on MySQL says he does this
exact thing all the time.  This link

  https://dev.mysql.com/doc/refman/5.1/en/udf-arguments.html

makes it seem that the arity of the function can vary.  So I am
confused by what you are saying.  I think overloading is a much better
way to solve this problem.

>>> Pasting here also the other two points you made, i.e. LOWER/UPPER and ILIKE.
>>> Probably there was not full discussion on them.
>>>
>>> LOWER/UPPER Initially they were set as optional for this revision, but
>>> there was also the point made that it would be better to have them
>>> mandatory...and also to have only one of them to help with tables
>>> indexing.
>>> Probably this is something to discuss.
>>
>> If anything we should be normalizing to upper case.  There are some
>> letters that do not round trip properly through lower case.
> 
> <cut>
> 
> it can be true also the other way around (scharfes S, e.g., even if
> unicode has an uppercase letter for it), but again I don't think the
> intent in adding these functions was to support all encodings and
> character sets, it pointed to correctly manage comparison for things
> like UCDs and Utypes.
> That's why ASCII was considered to be enough.

Looking at the Unicode spec, despite the example I gave before with ϱ,
it recommends case folding by lower casing everything.  Weird.  In any
case, if I implemented LOWER(), then implementing UPPER() would be
trivial.  In general, I do not like this idea of restricting the usage
of case-insensitivity functions to UCD's and Utypes.  We should put
them in for general use or not put them in at all.

Cheers,
Walter Landry