Re: 64-bit hash function for hstore and citext data type

>>>>> "Tomas" == Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com> writes:

Tomas> I wonder if the hstore hash function is actually correct. I see
Tomas> it pretty much just computes hash on the varlena representation.
Tomas> The important question is - can there be two different encodings
Tomas> for the same hstore value?

I was going to say "no", but in fact on closer examination there is an
edge case caused by the fact that hstoreUpgrade allows an _empty_ hstore
from pg_upgraded 8.4 data through without modifying it. (There's also a
vanishingly unlikely case involving the pgfoundry release of hstore-new.)

I'm inclined to fix this in hstoreUpgrade rather than complicate
hstore_hash with historical trivia. Also there have been no field
complaints - I guess it's unlikely that there is much pg 8.4 hstore data
in the wild that anyone wants to hash.

--
Andrew (irc:RhodiumToad)