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Diffstat (limited to 'lib/mnesia/src/mnesia_frag_old_hash.erl')
| -rw-r--r-- | lib/mnesia/src/mnesia_frag_old_hash.erl | 132 |
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 new file mode 100644 index 0000000000..817bb54eb1 --- /dev/null +++ b/lib/mnesia/src/mnesia_frag_old_hash.erl @@ -0,0 +1,132 @@ +%% +%% %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). |