Re: Remaining dependency on setlocale()

On 23.12.25 21:09, Jeff Davis wrote:
> On Wed, 2025-12-17 at 11:39 +0100, Peter Eisentraut wrote:
>> For Metaphone, I found the reference implementation linked from its
>> Wikipedia page, and it looks like our implementation is pretty
>> closely
>> aligned to that.  That reference implementation also contains the
>> C-with-cedilla case explicitly.  The correct fix here would probably
>> be
>> to change the implementation to work on wide characters.  But I think
>> for the moment you could try a shortcut like, use pg_ascii_toupper(),
>> but if the encoding is LATIN1 (or LATIN9 or whichever other encodings
>> also contain C-with-cedilla at that code point), then explicitly
>> uppercase that one as well.  This would preserve the existing
>> behavior.
> 
> Done, attached new patches.
> 
> Interestingly, WIN1256 encodes only the SMALL LETTER C WITH CEDILLA. I
> think, for the purposes here, we can still consider it to "uppercase"
> to \xc7, so that it can still be treated as the same sound. Technically
> I think that would be an improvement over the current code in this edge
> case, and suggests that case folding would be a better approach than
> uppercasing.

On further reflection, it seems just as easy to have dmetaphone() take 
the input collation and use that to do a proper collation-aware 
upper-casing.  This has the same effect (that is, it will still only 
support certain single-byte encodings), but it avoids elaborately 
hard-coding a bunch of things, and if we ever want to make this 
multibyte-aware, then we'll have to go this way anyway, I think.  See 
attached patch.