Re: Review: GiST support for UUIDs

> Or something like this in pseudocode:
>
> numeric = int8_numeric(*(uint64 *)(&i->data[0])) *
> int8_numeric(MAX_INT64) + int8_numeric(*(uint64 *)(&i->data[8]))

This is more like what I was hoping for, rather than converting to a
string and back. Would you mind confirming for me: int8_numeric turns an
int64 into an arbitrary-precision numeric Datum? So there is no overflow
risk here?

But it looks like int8_numeric takes a *signed* integer. Isn't that a
problem? I suppose I could get it working though by jumping through some
hoops.

> In UUID case you will take into account only half of value. Of
> course, GiST will work even with penalty function returning constant but
> each scan could become full-index-scan.

Yes, but that seems like an unrealistic concern. Even "only" 2^64 is
18446744073709551616 records. Or another way of thinking about it, if 64
bits (or 32) is a good enough penalty input for all the other data
types, why not for UUIDs? Keep in mind type 3-5 UUIDs should be evenly
distributed. Perhaps we could use the bottom half (instead of the top)
to ensure even distribution for type 1 and 2 too.

It seems to me that using only the top half should be okay, but if you
believe it's not I'll go with the int8_numeric approach (in three chunks
instead of two to work around signed-vs-unsigned).

Thanks,
Paul