-module(mnesia_frag_hash_test).
-export([test/0]).
-define(NUM_FRAGS, 20).
-define(NUM_KEYS, 10000).
-record(hash_state,
{n_fragments,
next_n_to_split,
n_doubles,
function}).
% OLD mnesia_frag_hash:key_to_frag_number/2.
old_key_to_frag_number(#hash_state{function = phash, next_n_to_split = SplitN, n_doubles = L}, Key) ->
P = SplitN,
A = erlang:phash(Key, power2(L)),
if
A < P ->
erlang:phash(Key, power2(L + 1));
true ->
A
end;
old_key_to_frag_number(#hash_state{function = phash2, next_n_to_split = SplitN, n_doubles = L}, Key) ->
P = SplitN,
A = erlang:phash2(Key, power2(L)) + 1,
if
A < P ->
erlang:phash2(Key, power2(L + 1)) + 1;
true ->
A
end;
old_key_to_frag_number(OldState, Key) ->
State = convert_old_state(OldState),
old_key_to_frag_number(State, Key).
% NEW mnesia_frag_hash:key_to_frag_number/2.
new_key_to_frag_number(#hash_state{function = phash, n_fragments = N, n_doubles = L}, Key) ->
A = erlang:phash(Key, power2(L + 1)),
if
A > N ->
A - power2(L);
true ->
A
end;
new_key_to_frag_number(#hash_state{function = phash2, n_fragments = N, n_doubles = L}, Key) ->
A = erlang:phash2(Key, power2(L + 1)) + 1,
if
A > N ->
A - power2(L);
true ->
A
end;
new_key_to_frag_number(OldState, Key) ->
State = convert_old_state(OldState),
new_key_to_frag_number(State, Key).
% Helpers for key_to_frag_number functions.
power2(Y) ->
1 bsl Y. % trunc(math:pow(2, Y)).
convert_old_state({hash_state, N, P, L}) ->
#hash_state{n_fragments = N,
next_n_to_split = P,
n_doubles = L,
function = phash}.
test() ->
test2(mnesia_frag_hash:init_state(undefined, undefined)), % phash2
test2({hash_state, 1, 1, 0}). % phash
test2(I) ->
test_keys(I),
lists:foldl(
fun(_, S) -> test_frag(S) end,
I, lists:seq(1, ?NUM_FRAGS)),
ok.
test_frag(State) ->
{State2,_,_} = mnesia_frag_hash:add_frag(State),
test_keys(State2),
State2.
test_keys(State) ->
[test_key(State, Key) || Key <- lists:seq(1, ?NUM_KEYS)].
test_key(State, Key) ->
Old = old_key_to_frag_number(State, Key),
New = new_key_to_frag_number(State, Key),
Old = New.
