Horton

Re: Add CASEFOLD() function.

Joe Conway <mail@joeconway.com>

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From: Joe Conway <mail@joeconway.com>
To: Jeff Davis <pgsql@j-davis.com>, Ian Lawrence Barwick <barwick@gmail.com>
Cc: pgsql-hackers@postgresql.org
Date: 2024-12-16T21:27:11Z
Lists: pgsql-hackers

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  1. Fix PDF doc build.

  2. Add SQL function CASEFOLD().

  3. Add support for Unicode case folding.

On 12/16/24 12:49, Jeff Davis wrote:
> One question I have is whether we want this function to normalize the
> output.
> 
> I believe most usecases would want the output normalized, because
> normalization differences (e.g. "a" U+0061 followed by "combining
> acute" U+0301 vs "a with acute" U+00E1) are more minor than differences
> in case.
> 
> Of course, a user could wrap it with the normalize() function, but
> that's verbose and easy to forget. I'm also not sure that it can be
> made as fast as a combined function that does both.

Perhaps a one arg version that always casefolds and a two arg version 
that accepts nfc, nfd, none (or something similar)?

> And a follow-up question: if it does normalize, the second parameter
> would be the requested normal form. But to accept the keyword forms
> (NFC, NFD in gram.y) rather than the string forms ('NFC', 'NFD') then
> we'd need to also need to add CASEFOLD to gram.y (like NORMALIZE). Is
> that a reasonable thing to do?

SQL 2023 seems to include the NORMALIZE syntax, but the only case 
folding considered is UPPER and LOWER. As such, I think it ought to be a 
function but not part of the grammar.

-- 
Joe Conway
PostgreSQL Contributors Team
RDS Open Source Databases
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