| From: | Greg Stark <stark(at)mit(dot)edu> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | "ktm(at)rice(dot)edu" <ktm(at)rice(dot)edu>, Peter Geoghegan <peter(at)2ndquadrant(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Greg Smith <greg(at)2ndquadrant(dot)com>, Magnus Hagander <magnus(at)hagander(dot)net>, Ants Aasma <ants(at)cybertec(dot)at>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Patch: add timing of buffer I/O requests |
| Date: | 2012-04-14 01:42:29 |
| Message-ID: | CAM-w4HPP+E7U=3CwSHao+Sv5237ngztx50-dD2r9UzTA-c7cEw@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Fri, Apr 13, 2012 at 8:15 PM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> That's probably true, but I'm not sure it's worth worrying about -
> one-in-four-billion is a pretty small probability.
Is this not subject to the birthday paradox? If you have a given hash
you're worried about a collision with then you have a
one-in-four-billion chance. But if you have a collection of hashes and
you're worried about any collisions then it only takes about 64k
before there's likely a collision.
--
greg
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