On Wed, Jul 24, 2024 at 1:45 PM Jeff Davis <pgsql@j-davis.com> wrote: > There's a qualitative difference between a collation update which can > break your PKs and FKs, and a ctype update which definitely will not.
I don't think that's true. All you need is a unique index on UPPER(somecol).
I doubt it’s common to have unique on upper()
But non-unique indexes for case insensitive searches will be more common. Historically this is the most common way people did case insensitive on oracle.
Changing ctype would mean these queries can return wrong results
The impact would be similar to the critical problem TripAdvisor hit in 2014 with their read replicas, in the Postgres email thread I linked above