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%%% Copyright (c) 2014, NORDUnet A/S.
%%% See LICENSE for licensing information.
-module(db).
-behaviour(gen_server).
%% API.
-export([start_link/0, stop/0]).
-export([init_db/0, init_db/1, init_tables/0, init_tables/1]).
-export([add/1, find/1, get_by_index/2, get_by_index_sorted/2, size/0]).
%% API for testing.
-export([dump/1, destroy_tables/0, info_tables/0, dump_to_file/1]).
%% gen_server callbacks.
-export([init/1, handle_call/3, terminate/2, handle_cast/2, handle_info/2,
code_change/3]).
-include_lib("stdlib/include/qlc.hrl").
-include("db.hrl").
-include("$CTROOT/plop/include/plop.hrl").
%% @doc Set up a database schema on all nodes that are to be included
%% in the "database cluster". Has to be run _before_ mnesia has been
%% started.
init_db() ->
init_db([node()]).
init_db(Nodes) ->
ok = mnesia:create_schema(Nodes),
rpc:multicall(Nodes, application, start, [mnesia]),
init_tables(Nodes),
rpc:multicall(Nodes, application, stop, [mnesia]).
%% @doc Run once, or rather every time you start on a new database.
%% If run more than once, we'll get {aborted, {already_exists, TABLE}}.
init_tables() ->
init_tables([node()]).
init_tables(Nodes) ->
%% We've once upon a time invoked mnesia:create_schema/1 with the
%% nodes that will be part of the database.
RamCopies = [],
DiscCopies = [],
DiscOnlyCopies = Nodes,
mnesia:start(),
{atomic, ok} =
mnesia:create_table(plop,
[{type, set},
{ram_copies, RamCopies},
{disc_copies, DiscCopies},
{disc_only_copies, DiscOnlyCopies},
{attributes, record_info(fields, plop)},
{majority, true}]),
{atomic, ok} = mnesia:add_table_index(plop, hash).
destroy_tables() ->
mnesia:delete_table(plop).
info_tables() ->
mnesia:table_info(plop, all).
dump_to_file(Filename) ->
mnesia:dump_to_textfile(Filename).
size() ->
mnesia:table_info(plop, size).
init(_Args) ->
{mnesia:wait_for_tables([plop], 5000), []}.
start_link() ->
gen_server:start_link({local, ?MODULE}, ?MODULE, [], []).
stop() ->
gen_server:call(?MODULE, stop).
%%%%%%%%%%%%%%%%%%%%
%% Public API.
add(Entry) ->
gen_server:call(?MODULE, {add, Entry}).
find(Hash) ->
gen_server:call(?MODULE, {find, Hash}).
dump(Table) ->
gen_server:call(?MODULE, {dump, Table}).
get_by_index(Start, End) ->
gen_server:call(?MODULE, {get_by_index, {Start, End}}).
get_by_index_sorted(Start, End) ->
gen_server:call(?MODULE, {get_by_index_sorted, {Start, End}}).
%%%%%%%%%%%%%%%%%%%%
%% gen_server callbacks.
handle_cast(_Request, State) ->
{noreply, State}.
handle_info(_Info, State) ->
{noreply, State}.
code_change(_OldVsn, State, _Extra) ->
{ok, State}.
terminate(_Reason, _State) ->
io:format("~p terminating~n", [?MODULE]),
ok.
%%%%%%%%%%%%%%%%%%%%
%% The meat.
handle_call(stop, _From, State) ->
{stop, normal, stopped, State};
handle_call({add, Entry}, _From, State) ->
F = fun() ->
mnesia:write(Entry)
end,
Res = mnesia:transaction(F),
{reply, Res, State};
handle_call({dump, Table}, _From, State) ->
F = fun() ->
Q = qlc:q([E || E <- mnesia:table(Table)]),
qlc:e(Q)
end,
Res = mnesia:transaction(F),
{reply, Res, State};
handle_call({find, Hash}, _From, State) ->
F = fun() ->
mnesia:index_read(plop, Hash, #plop.hash)
end,
{atomic, Result} = mnesia:transaction(F),
Record = case length(Result) of
0 -> [];
1 -> hd(Result);
_ -> duplicate_hash_in_db % FIXME: log an error
end,
{reply, Record, State};
handle_call({get_by_index, {Start, End}}, _From, State) ->
Res = [X || [_, X] <- select_index(Start, End)],
{reply, Res, State};
handle_call({get_by_index_sorted, {Start, End}}, _From, State) ->
%% FIXME: RAM hog -- how bad is it?
Res = [X || [_, X] <- lists:sort(select_index(Start, End))],
{reply, Res, State}.
%%%%%%%%%%%%%%%%%%%%
%% Helper functions.
select_index(Start, End) ->
F = fun() ->
MatchHead = #plop{index = '$1', mtl = '$2', _ = '_'},
Guard = [{'>=', '$1', Start}, {'=<', '$1', End}],
Result = ['$$'],
mnesia:select(plop, [{MatchHead, Guard, Result}])
end,
{atomic, Res} = mnesia:transaction(F),
Res.
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