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-rw-r--r--lib/mnesia/src/mnesia_frag_old_hash.erl132
1 files changed, 132 insertions, 0 deletions
diff --git a/lib/mnesia/src/mnesia_frag_old_hash.erl b/lib/mnesia/src/mnesia_frag_old_hash.erl
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+%%
+%% %CopyrightBegin%
+%%
+%% Copyright Ericsson AB 2002-2009. All Rights Reserved.
+%%
+%% The contents of this file are subject to the Erlang Public License,
+%% Version 1.1, (the "License"); you may not use this file except in
+%% compliance with the License. You should have received a copy of the
+%% Erlang Public License along with this software. If not, it can be
+%% retrieved online at http://www.erlang.org/.
+%%
+%% Software distributed under the License is distributed on an "AS IS"
+%% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
+%% the License for the specific language governing rights and limitations
+%% under the License.
+%%
+%% %CopyrightEnd%
+%%
+
+%%
+%%%----------------------------------------------------------------------
+%%% Purpose : Implements hashing functionality for fragmented tables
+%%%----------------------------------------------------------------------
+
+-module(mnesia_frag_old_hash).
+%%-behaviour(mnesia_frag_hash).
+
+-compile({nowarn_deprecated_function, {erlang,hash,2}}).
+
+%% Hashing callback functions
+-export([
+ init_state/2,
+ add_frag/1,
+ del_frag/1,
+ key_to_frag_number/2,
+ match_spec_to_frag_numbers/2
+ ]).
+
+-record(old_hash_state,
+ {n_fragments,
+ next_n_to_split,
+ n_doubles}).
+
+%% Old style. Kept for backwards compatibility.
+-record(frag_hash,
+ {foreign_key,
+ n_fragments,
+ next_n_to_split,
+ n_doubles}).
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+init_state(_Tab, InitialState) when InitialState == undefined ->
+ #old_hash_state{n_fragments = 1,
+ next_n_to_split = 1,
+ n_doubles = 0};
+init_state(_Tab, FH) when is_record(FH, frag_hash) ->
+ %% Old style. Kept for backwards compatibility.
+ #old_hash_state{n_fragments = FH#frag_hash.n_fragments,
+ next_n_to_split = FH#frag_hash.next_n_to_split,
+ n_doubles = FH#frag_hash.n_doubles}.
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+add_frag(State) when is_record(State, old_hash_state) ->
+ SplitN = State#old_hash_state.next_n_to_split,
+ P = SplitN + 1,
+ L = State#old_hash_state.n_doubles,
+ NewN = State#old_hash_state.n_fragments + 1,
+ State2 = case trunc(math:pow(2, L)) + 1 of
+ P2 when P2 == P ->
+ State#old_hash_state{n_fragments = NewN,
+ next_n_to_split = 1,
+ n_doubles = L + 1};
+ _ ->
+ State#old_hash_state{n_fragments = NewN,
+ next_n_to_split = P}
+ end,
+ {State2, [SplitN], [NewN]}.
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+del_frag(State) when is_record(State, old_hash_state) ->
+ P = State#old_hash_state.next_n_to_split - 1,
+ L = State#old_hash_state.n_doubles,
+ N = State#old_hash_state.n_fragments,
+ if
+ P < 1 ->
+ L2 = L - 1,
+ MergeN = trunc(math:pow(2, L2)),
+ State2 = State#old_hash_state{n_fragments = N - 1,
+ next_n_to_split = MergeN,
+ n_doubles = L2},
+ {State2, [N], [MergeN]};
+ true ->
+ MergeN = P,
+ State2 = State#old_hash_state{n_fragments = N - 1,
+ next_n_to_split = MergeN},
+ {State2, [N], [MergeN]}
+ end.
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+key_to_frag_number(State, Key) when is_record(State, old_hash_state) ->
+ L = State#old_hash_state.n_doubles,
+ A = erlang:hash(Key, trunc(math:pow(2, L))),
+ P = State#old_hash_state.next_n_to_split,
+ if
+ A < P ->
+ erlang:hash(Key, trunc(math:pow(2, L + 1)));
+ true ->
+ A
+ end.
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+match_spec_to_frag_numbers(State, MatchSpec) when is_record(State, old_hash_state) ->
+ case MatchSpec of
+ [{HeadPat, _, _}] when is_tuple(HeadPat), tuple_size(HeadPat) > 2 ->
+ KeyPat = element(2, HeadPat),
+ case has_var(KeyPat) of
+ false ->
+ [key_to_frag_number(State, KeyPat)];
+ true ->
+ lists:seq(1, State#old_hash_state.n_fragments)
+ end;
+ _ ->
+ lists:seq(1, State#old_hash_state.n_fragments)
+ end.
+
+has_var(Pat) ->
+ mnesia:has_var(Pat).