Re: Multi-byte character case-folding

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От Tom Lane
Тема Re: Multi-byte character case-folding
Дата
Msg-id 1517069.1594126907@sss.pgh.pa.us
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Ответ на Re: Multi-byte character case-folding  ("Daniel Verite" <daniel@manitou-mail.org>)
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"Daniel Verite" <daniel@manitou-mail.org> writes:
>     Tom Lane wrote:
>> If we start to case-fold É, then the only way to access this table will
>> be by double-quoting its name, which the application probably is not
>> expecting (else it would have double-quoted in the original CREATE TABLE).

> This problem already exists when migrating from a mono-byte database
> to a multi-byte database, since downcase_identifier()  does use
> tolower() for mono-byte databases.

Sure, but that's a tiny minority of use-cases.  In particular it would
not bite you after a straight upgrade to a new PG version.

[ thinks... ]  Wait, actually the described case would occur if you
migrated *from* UTF8 (no folding) to LATINn (with folding).  That's
gotta be an even tinier minority.  Migration to UTF8 would show
different, though perhaps just as annoying, symptoms.

Anyway, I freely concede that I'm ill-equipped to judge how annoying
this is, since I don't program in any languages where it'd make a
difference.  But we mustn't fool ourselves: changing this would be
just as dangerous as the standard_conforming_strings changeover was.
I'm not really convinced it's worth it.  In particular, I don't find
the "it's required by the standard" argument convincing.  The standard
requires us to fold to upper case, too, but we've long ago decided to
just say no to that.  (Which reminds me: there are extensive threads in
the archives analyzing whether it's practical to support more than one
folding behavior.  Those discussions would likely be relevant here.)

            regards, tom lane



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