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.
