Re: 64-bit queryId?

On Sat, Sep 30, 2017 at 12:34 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
>> How about widening the value to uint64?
>
> Doesn't really seem like that would guarantee no collisions.

Well, no duh. If you come up with a hash function that maps an
infinite domain onto a finite range while guaranteeing no collisions,
I will look forward to reading the paper with interest.

Assuming, however, that you don't manage to prove all known
mathematics inconsistent, what one might reasonably hope to do is
render collisions remote enough that one need not worry about them too
much in practice. From that point of view, reducing the probability
of a collision by several orders of magnitude seems worth doing if (1)
the cost isn't too much and (2) the probability of a collision as
things stand is significant. I argue that both of those things are
probably true.

--
Robert Haas
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