On Thu, 2006-02-16 at 21:33 -0800, David Lang wrote: > > In SQL_ASCII, just take the first 4 characters (or 8, if using a 64-bit > > sortKey as elsewhere suggested). The sorting key doesn't need to be a > > one-to-one mapping. > > that would violate your second contraint ( f(a)==f(b) iff (a==b) ) > > if you could drop that constraint (the cost of which would be extra 'real' > compares within a bucket) then a helper function per datatype could work > as you are talking. I think we're actually on the same page here; you're right that the constraint above ( f(a)==f(b) iff a==b ) can't be extended to data types with more than 32 bits of value space. But the constraint I listed was actually: if a==b then f(a)==f(b) Which doesn't imply 'if and only if'. It's a similar constraint to hashcodes; the same value will always have the same hash, but you're not guaranteed that the hashcodes for two distinct values will be unique. -- Mark
