Re: Use CASEFOLD() internally rather than LOWER() - Mailing list pgsql-hackers
On Wed, Mar 25, 2026 at 2:02 PM Jeff Davis <pgsql@j-davis.com> wrote:
I think the precise question would be: "are there any two characters
that lowercase to the same character but do not casefold to the same
character?".
I don't know. I'll set up a test to iterate across all locales across all character pairs... no, I didn't find any on my system. Other searching suggests that the Turkish and Azerbaijani locale do have this characteristic, with I (U+0049) lowercasing to ı (U+0131) and case folding to i (U+0069) while ı (U+0131) lowercases to ı (U+0131) but also case folds to ı (U+0131). I have not confirmed that empirically, though.
I don't have a counterexample, so perhaps using casefold would still be
fine.
Thoughts? Should we enhance regexes to consider more than two case
variants first, or should we proceed with some of these patches (and/or
a similar change to pg_trgm)?
I don't want to take a strong position either way. I'm still wrapping my head around the various implications of the proposed changes, and don't feel I have a complete picture yet.
Mark Dilger
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