Re: Hash Functions

Hi,

On 2017-05-14 21:22:58 -0400, Robert Haas wrote:
> but wanting a CHECK constraint that applies to only one partition
> seems pretty reasonable (e.g. CHECK that records for older years are
> all in the 'inactive' state, or whatever).

On a hash-partitioned table?

> Now that's not to say that we shouldn't have a
> reload-through-the-top-parent switch; actually, I think that's a good
> idea. I just don't believe that it can ever be a complete substitute
> for portable hash functions. I think almost everybody here agrees
> that it isn't necessary to have hash functions that are 100% portable,
> e.g. to VAX. But it would be nice IMHO if you could use an integer
> column as the partitioning key and have that be portable between Intel
> and POWER.

I'm not saying it can't work for any datatype, I just think it'd be a
very bad idea to make it work for any non-trivial ones. The likelihood
of reguarly breaking or preventing us from improving things seems high.
I'm not sure that having a design where this most of the time works for
some datatypes is a good one.

Greetings,

Andres Freund