On Wed, Feb 1, 2023 at 12:39 PM Robert Haas <robertmhaas@gmail.com> wrote:
> I don't think the fact that our *traditional* standard for how stable
> a hash function needs to be has been XYZ carries any water. Needs
> change over time, and we adapt the code to meet the new needs. Since
> we have no system for type properties in PostgreSQL -- a design
> decision I find questionable -- we tie all such properties to operator
> classes.
Are you familiar with B-Tree opclass support function 4, equalimage?
It's used to determine whether a B-Tree index can use deduplication at
CREATE INDEX time. ISTM that the requirements are rather similar here
-- perhaps even identical.
See: https://www.postgresql.org/docs/devel/btree-support-funcs.html
--
Peter Geoghegan