Re: [PATCHES] updated hash functions for postgresql v1

On Wed, Oct 28, 2009 at 03:31:17PM -0400, Tom Lane wrote:
> Hannu Krosing <hannu@2ndQuadrant.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

In addition that change from 8.3 -> 8.4 to store only the hash and not
the value in the index means that a reindex would be required in any event.

Cheers,
Ken