On Wed, Feb 1, 2023 at 12:39 PM Robert Haas <robertmh...@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
