Hannu Krosing <hannu(at)2ndQuadrant(dot)com> writes:
> I had never checked the docs for hash functions, but I had assumed, that
> internal functions are prefixed by pg_ and anything else is public, free
> to use functionality.
Sure, it's free to use. It's not free to assume that we promise never
to change it.
> Changing hash functions also makes in-place upgrades a lot harder, as
> they can't be done incrementally anymore for tables which use hash
> indexes.
Hash indexes are so far from being production-grade that this argument
is not significant.
regards, tom lane