Hi Olav. As you have observed the key length of the generated keys is not
guaranteed.
riak_core_util:unique_id_62 generates a 20 byte SHA hash and that value is
converted to a base 62
representation and that representation, converted to a string, becomes the key.
The length of the
generated key can be determined by taking the ceiling of the value of log62(X),
where X is the integer value
of the SHA result. So the length of the key is going to be dependent on the
magnitude of the
value of that SHA.
That means that right now the answer is there is not a way to enforce that all
keys generated
by Riak be of the exact same length. If that is a requirement for your
application you will
have to generate them on the client side.
Cheers,
Kelly
On Nov 6, 2012, at 4:55 AM, Olav Frengstad <o...@fwt.no> wrote:
> Hey,
>
> I'm using keys generated by Riak and have come over some random
> failure in my test cases. I have naively assumed that the 160bit hash
> would always return a base62 encoded value with the length of 27. On
> that point I'm obviously wrong as the shell session below shows.
>
> My question is this by design? If so is there a way to enforce certain
> size of a key WITHOUT performing generation outside Riak?
>
> Test of riak key size:
>
> 72> P = fun(S) -> put(S, case get(S) of undefined -> 1; X -> X+1 end) end.
> #Fun<erl_eval.6.82930912>
> 73> F = fun(X, A) when A =< 1000000 ->
> P(length(riak_core_util:unique_id_62())), X(X, A+1); (_, A) -> A end.
> #Fun<erl_eval.12.82930912>
> 74> F(F, 0).
> 1000001
> 75> erlang:process_info(self(), dictionary).
> {dictionary,[{27,982324},{26,27210},{25,461},{24,7}]}
>
> Cheers,
> Olav
>
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