Groups > comp.databases.postgresql > #650

Re: how to count the number of ipv6 addresses in a range?

From	Ralf Döblitz <doeblitz@doeblitz.net>
Newsgroups	comp.databases.postgresql
Subject	Re: how to count the number of ipv6 addresses in a range?
Date	2015-04-03 13:17 +0000
Organization	private site in Braunschweig, Germany
Message-ID	<mfm3u7$lr8$2@selene.doeblitz.net> (permalink)
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Mateusz Viste <mateusz.viste@localhost> wrote:
> On 02/04/2015 18:48, Ralf Döblitz wrote:
>> I would use the binary logarithm of the number of addresses.
> 
> That's the core of the problem in fact :) the "number of addresses" is 
> uncomputable, so any transformation thereof is not possible either:
> 
>   nsidb=# select log(2,('ff00::'::inet - 'fd00::'::inet));
>   ERROR:  result is out of range
>   nsidb=#

Looks like you will have to program that computation yourself to avoid
getting overflows for interim results. Build the complete bitmaps of the
addresses, compare them for matching leading part, then advance to the
end, incrementally calculating the sum with the desired precision (maybe
the number of /64 nets is sufficient for your purpose).

Ralf
-- 
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how to count the number of ipv6 addresses in a range? Mateusz Viste <mateusz.viste@localhost> - 2015-03-30 18:43 +0200
  Re: how to count the number of ipv6 addresses in a range? "M. Strobel" <strobel@example.com> - 2015-03-30 22:13 +0200
    Re: how to count the number of ipv6 addresses in a range? "M. Strobel" <strobel@example.com> - 2015-03-31 01:25 +0200
    Re: how to count the number of ipv6 addresses in a range? Mateusz Viste <mateusz.viste@localhost> - 2015-03-31 09:39 +0200
      Re: how to count the number of ipv6 addresses in a range? "M. Strobel" <strobel@example.com> - 2015-03-31 09:56 +0200
        Re: how to count the number of ipv6 addresses in a range? Mateusz Viste <mateusz.viste@localhost> - 2015-03-31 11:03 +0200
      Re: how to count the number of ipv6 addresses in a range? Ralf Döblitz <doeblitz@doeblitz.net> - 2015-04-02 16:48 +0000
        Re: how to count the number of ipv6 addresses in a range? Mateusz Viste <mateusz.viste@localhost> - 2015-04-03 09:09 +0200
          Re: how to count the number of ipv6 addresses in a range? Ralf Döblitz <doeblitz@doeblitz.net> - 2015-04-03 13:17 +0000

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