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mnesia_ext_filesystem.erl
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mnesia_ext_filesystem.erl
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%%
%% %CopyrightBegin%
%%
%% Copyright Ericsson AB 1996-2014. All Rights Reserved.
%%
%% Licensed under the Apache License, Version 2.0 (the "License");
%% you may not use this file except in compliance with the License.
%% You may obtain a copy of the License at
%%
%% http://www.apache.org/licenses/LICENSE-2.0
%%
%% Unless required by applicable law or agreed to in writing, software
%% distributed under the License is distributed on an "AS IS" BASIS,
%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
%% See the License for the specific language governing permissions and
%% limitations under the License.
%%
%% %CopyrightEnd%
%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% TODO: the external plugin framework has been developed further, and
%% this plugin is not updated accordingly. Therefore there might be
%% some incompatibilities!!
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%
%% External filesystem storage backend for mnesia.
%% Usage: mnesia:create_table(Tab, [{external, [
%% {mnesia_ext_filesystem, Nodes}]}, ...]).
-module(mnesia_ext_filesystem).
-behaviour(mnesia_backend_type).
%% -compile(export_all).
-export([register/0,
types/0,
valid_op/2]).
%%
-export([
add_aliases/1,
check_definition/4,
create_table/3,
delete/3,
delete_table/2,
load_table/4,
close_table/2,
sync_close_table/2,
first/2,
fixtable/3,
index_is_consistent/3,
init_backend/0,
info/3,
insert/3,
is_index_consistent/2,
last/2,
lookup/3,
match_delete/3,
next/3,
prev/3,
real_suffixes/0,
remove_aliases/1,
repair_continuation/2,
select/1,
select/3,
select/4,
semantics/2,
slot/3,
tmp_suffixes/0,
update_counter/4,
validate_key/6,
validate_record/6
]).
-export([sender_init/4,
sender_handle_info/5,
receiver_first_message/4,
receive_data/5,
receive_done/4
]).
%% record and key validation
%% table process start and callbacks
-export([start_proc/3,
init/1,
handle_call/3,
handle_info/2,
handle_cast/2,
terminate/2,
code_change/3]).
-include("../src/mnesia.hrl").
-include_lib("kernel/include/file.hrl").
%% -record(info, {tab,
%% key,
%% fullname,
%% recname}).
-record(sel, {alias,
tab,
type,
recname,
mp,
keypat,
ms,
limit,
key_only = false,
direction = forward}).
-record(st, {ets,
dets,
mp,
data_mp,
alias,
tab}).
register() ->
mnesia_schema:schema_transaction(
fun() ->
[mnesia_schema:do_add_backend_type(T, M)
|| {T, M} <- types()]
end).
types() ->
[{fs_copies, ?MODULE},
{raw_fs_copies, ?MODULE}].
semantics(_Alias, storage) -> disc_only_copies;
semantics(_Alias, types ) -> [set, ordered_set];
semantics(_Alias, index_types) -> [ordered];
semantics(_Alias, _) ->
undefined.
valid_op(_, _) ->
true.
init_backend() ->
ok.
add_aliases(_) ->
ok.
remove_aliases(_) ->
ok.
%% ===========================================================
%% Table synch protocol
%% Callbacks are
%% Sender side:
%% 1. sender_init(Alias, Tab, RemoteStorage, ReceiverPid) ->
%% {InitFun :: fun() -> {Recs, Cont} | '$end_of_table',
%% ChunkFun :: fun(Cont) -> {Recs, Cont1} | '$end_of_table'}
%% 2. InitFun() is called
%% 3a. ChunkFun(Cont) is called repeatedly until done
%% 3b. sender_handle_info(Msg, Alias, Tab, ReceiverPid, Cont) ->
%% {ChunkFun, NewCont}
%%
%% Receiver side:
%% 1. receiver_first_message(SenderPid, Msg, Alias, Tab) ->
%% {Size::integer(), State}
%% 2. receive_data(Data, Alias, Tab, _Sender, State) ->
%% {more, NewState} | {{more, Msg}, NewState}
%% 3. receive_done(_Alias, _Tab, _Sender, _State) ->
%% ok
%%
%% The receiver can communicate with the Sender by returning
%% {{more, Msg}, St} from receive_data/4. The sender will be called through
%% sender_handle_info(Msg, ...), where it can adjust its ChunkFun and
%% Continuation. Note that the message from the receiver is sent once the
%% receive_data/4 function returns. This is slightly different from the
%% normal mnesia table synch, where the receiver acks immediately upon
%% reception of a new chunk, then processes the data.
%%
sender_init(Alias, Tab, RemoteStorage, Pid) ->
%% Need to send a message to the receiver. It will be handled in
%% receiver_first_message/4 below. There could be a volley of messages...
{ext, Alias, ?MODULE} = RemoteStorage, % limitation for now
Pid ! {self(), {first, info(Alias, Tab, size)}},
receive
{Pid, Reply} ->
io:fwrite("Receiver (~p) replies: ~p~n", [Pid, Reply])
after 30000 ->
erlang:error(timeout_waiting_for_receiver)
end,
MP = data_mountpoint(Tab),
{fun() ->
{ok, Fs} = file:list_dir(MP),
FI = fetch_files(Fs, MP),
{[{[], FI}], {[F || {F,dir} <- FI], MP, MP,
fun() -> '$end_of_table' end}}
end,
chunk_fun()}.
sender_handle_info(_Msg, _Alias, _Tab, _ReceiverPid, Cont) ->
%% ignore - we don't expect any message from the receiver
{chunk_fun(), Cont}.
chunk_fun() ->
fun(Cont) ->
fetch_more_files(Cont)
end.
fetch_files([F|Fs], Dir) ->
Fn = filename:join(Dir, F),
case file:read_file(Fn) of
{error, eisdir} ->
[{F, dir}|fetch_files(Fs, Dir)];
{ok, Bin} ->
[{F, Bin}|fetch_files(Fs, Dir)];
{error, enoent} ->
%% ouch!
fetch_files(Fs, Dir)
end;
fetch_files([], _) ->
[].
fetch_more_files({[], _, _, C}) ->
C();
fetch_more_files({[F|Fs], Dir, MP, C}) ->
D = filename:join(Dir, F),
case file:list_dir(D) of
{error, enoent} ->
io:fwrite("Not found: ~s~n", [D]),
fetch_more_files({Fs, Dir, MP, C});
{ok, Fs1} ->
Fs1i = fetch_files(Fs1, D),
{[{remove_top(MP, D), Fs1i}], {[Fx || {Fx,dir} <- Fs1i], D, MP,
fun() -> fetch_more_files({Fs, Dir, MP, C}) end}}
end.
receiver_first_message(Pid, {first, Size} = _Msg, _Alias, _Tab) ->
io:fwrite("~p:receiver_first_message (~p): ~p~n", [?MODULE, Pid, _Msg]),
Pid ! {self(), "Hello Joe..."},
{Size, _State = []}.
receive_data(Data, Alias, Tab, _Sender, State) ->
MP = data_mountpoint(Tab),
N = store_data(Data, Alias, Tab, MP, 0),
call(Alias, Tab, {incr_size, N}),
{more, State}.
receive_done(_Alias, _Tab, _Sender, _State) ->
ok.
store_data([], _, _, _, N) ->
N;
store_data([{Dir, Fs}|T], Alias, Tab, MP, N) ->
Dirname = filename:join(MP, Dir),
N1 = case list_dir(Dirname) of
{error, enoent} ->
fill_empty(Dirname, Fs, N);
{error, enotdir} ->
N11 = delete_file_or_dir(Dirname, N),
store_data([{Dir, Fs}|T], Alias, Tab, MP, N11);
{ok, MyFs} ->
diff_dirs(MyFs, Fs, Dirname, N)
end,
store_data(T, Alias, Tab, MP, N1).
list_dir(Dirname) ->
file:list_dir(Dirname).
make_dir(D) -> file:make_dir(D).
del_dir(D) -> file:del_dir(D).
delete_file(F) -> file:delete(F).
write_file(F,B) -> file:write_file(F, B).
fill_empty(Dirname, Fs, N) ->
make_dir(Dirname),
lists:foldl(fun({F, dir}, Acc) ->
file:make_dir(filename:join(Dirname, F)),
Acc;
({F, Bin}, Acc) when is_binary(Bin) ->
file:write_file(filename:join(Dirname, F), Bin),
Acc + 1
end, N, Fs).
diff_dirs(MyFs, Fs, Dirname, N) ->
N1 = lists:foldl(
fun(F, Acc) ->
case lists:keymember(F, 1, Fs) of
false ->
delete_file_or_dir(filename:join(Dirname,F), Acc);
true ->
Acc
end
end, N, MyFs),
lists:foldl(
fun({F,dir}, Acc) ->
Fname = filename:join(Dirname, F),
case make_dir(Fname) of
{error, eexist} ->
case filelib:is_regular(Fname) of
true ->
delete_file(Fname),
make_dir(Fname),
Acc - 1;
false ->
Acc
end;
ok ->
Acc
end;
({F,Bin}, Acc) when is_binary(Bin) ->
Fname = filename:join(Dirname, F),
case write_file(Fname, Bin) of
{error, eisdir} ->
N = delete_file_or_dir(Fname),
write_file(Fname, Bin),
Acc+1-N;
ok ->
Acc+1
end
end, N1, Fs).
delete_file_or_dir(F) ->
delete_file_or_dir(F, 0).
delete_file_or_dir(F, N) ->
case delete_file(F) of
{error, eisdir} ->
{ok, Fs} = list_dir(F),
N1 = lists:foldl(fun(F1, Acc) ->
Fn = filename:join(F, F1),
delete_file_or_dir(Fn, Acc)
end, N, Fs),
ok = del_dir(F),
N1;
ok ->
N+1
end.
%% End of table synch protocol
%% ===========================================================
validate_key(Alias, Tab, RecName, Arity, Type, Key) ->
%% RecName, Arity and Type have already been validated
try begin
NewKey = encode_key(Alias, Tab, Key),
is_legal_key(Alias, Tab, NewKey),
{RecName, Arity, Type}
end
catch
error:_ -> mnesia:abort(bad_type, [Tab, Key])
end.
is_legal_key(raw_fs_copies, Tab, Key) ->
MP = data_mountpoint(Tab),
FN = fullname(Tab, Key, MP),
case file:read_file_info(FN) of
{error, enoent} ->
case is_valid_dir(FN, MP) of
ok ->
ok;
Other ->
mnesia:abort(Other)
end;
{error, _} = OtherErr ->
mnesia:abort(OtherErr);
{ok, #file_info{type = regular}} ->
ok;
{ok, #file_info{type = directory}} ->
mnesia:abort({error, eisdir})
end;
is_legal_key(_, _, _) ->
ok.
is_valid_dir(D, D) ->
ok;
is_valid_dir(F, MP) ->
D = filename:dirname(F),
case file:read_file_info(D) of
{error, enoent} ->
is_valid_dir(D, MP);
{ok, #file_info{type = directory,
access = Access}} ->
if Access == read_write ->
ok;
true ->
{error, eacces}
end;
{ok, #file_info{}} ->
{error, enotdir}
end.
validate_record(Alias, Tab, RecName, Arity, Type, Obj) ->
%% RecName, Arity and Type have already been validated
Key = encode_key(Alias, Tab, element(2, Obj)),
is_legal_key(Alias, Tab, Key),
{RecName, Arity, Type}.
encode_key(fs_copies, Tab, Key) ->
split_key(sext_encode(Key));
encode_key(raw_fs_copies, Tab, Key) ->
if is_binary(Key) ->
binary_to_list(Key);
is_list(Key) ->
binary_to_list(list_to_binary(Key));
is_atom(Key) ->
atom_to_list(Key);
true ->
mnesia:abort({bad_type, [Tab, Key]})
end.
decode_key(Key, fs_copies, _) ->
sext_decode(unsplit_key(list_to_binary([Key])));
decode_key(Key, _, _) ->
Key.
sext_encode(K) ->
mnesia_sext:encode_sb32(K).
sext_decode(K) ->
mnesia_sext:decode_sb32(K).
split_key(K) when is_binary(K) ->
binary_to_list(split_key1(K)).
split_key1(<<A,B,C,T/binary>>) ->
<<A,B,C,$/, (split_key1(T))/binary>>;
split_key1(Bin) ->
Bin.
unsplit_key(Bin) ->
<< <<C>> || <<C>> <= Bin,
C =/= $/ >>.
create_table(_Alias, Tab, _Props) ->
create_mountpoint(Tab),
ok.
delete_table(_Alias, Tab) ->
MP = get_mountpoint(Tab),
assert_proper_mountpoint(Tab, MP),
os:cmd("rm -r " ++ MP).
assert_proper_mountpoint(_Tab, _MP) ->
%% not yet implemented. How to verify that the MP var points to the
%% directory we actually want deleted?
ok.
prop(K,Props) ->
proplists:get_value(K, Props).
check_definition(Alias, Tab, Nodes, Props)
when Alias==fs_copies; Alias==raw_fs_copies ->
Id = {Alias, Nodes},
[Rc, Dc, DOc] =
[proplists:get_value(K,Props,[]) || K <- [ram_copies,
disc_copies,
disc_only_copies]],
case {Rc,Dc,DOc} of
{[],[],[]} ->
case prop(type, Props) of
ordered_set -> ok;
set -> ok;
Type -> mnesia:abort({combine_error, Tab, [Id, {type, Type}]})
end,
MP = get_mountpoint(Tab),
case dir_exists_or_creatable(MP) of
true ->
ok;
false ->
mnesia:abort({bad_mountpoint, Tab, [MP]})
end,
case {Alias, prop(attributes, Props)} of
{raw_fs_copies, [_Key, _Value]} ->
ok;
{fs_copies, _} ->
ok;
Attrs ->
mnesia:abort({invalid_attributes, Tab, Attrs})
end;
_ ->
X = fun(_, []) -> [];
(T, [_|_]=Ns) -> [{T, Ns}]
end,
mnesia:abort({combine_error, Tab,
[Id |
X(ram_copies, Rc) ++ X(disc_copies, Dc) ++
X(disc_only_copies,DOc)]})
end.
%%
info_mountpoint(Tab) ->
Dir = mnesia_monitor:get_env(dir),
filename:join(Dir, tabname(Tab) ++ ".extfsi").
data_mountpoint(Tab) ->
get_mountpoint(Tab).
%%
get_mountpoint(Tab) ->
L = mnesia_monitor:get_env(filesystem_locations),
case lists:keyfind(Tab, 1, L) of
false ->
default_mountpoint(Tab);
{_, Loc} ->
Loc
end.
default_mountpoint(Tab) ->
Dir = mnesia_monitor:get_env(dir),
filename:join(Dir, tabname(Tab) ++ ".extfs").
real_suffixes() ->
[".extfs", ".extfsi"].
tmp_suffixes() ->
[].
%% pos(A, Attrs) -> pos(A, Attrs, 1).
%% pos(A, [A|_], P) -> P;
%% pos(A, [_|T], P) -> pos(A, T, P+1);
%% pos(_, [], _) -> 0.
my_file_info(F) ->
case file:read_link_info(F) of
{ok, #file_info{type = symlink}} ->
case file:read_link(F) of
{ok, NewF} ->
my_file_info(NewF);
Other ->
Other
end;
Other ->
Other
end.
parent_dir(F) ->
case filename:split(F) of
["."] ->
parent_dir(filename:absname(F));
[_] ->
F;
_ ->
filename:dirname(F)
end.
is_writable(D) ->
case my_file_info(D) of
{ok, #file_info{type = directory, access = A}}
when A == write; A == read_write ->
true;
_ ->
false
end.
dir_exists_or_creatable(Dir) ->
case my_file_info(Dir) of
{ok, #file_info{type = directory}} ->
true;
{error, enoent} ->
is_writable(parent_dir(Dir));
_Other ->
false
end.
create_mountpoint(Tab) ->
MP = get_mountpoint(Tab),
file:make_dir(MP),
file:make_dir(data_mountpoint(Tab)),
file:make_dir(info_mountpoint(Tab)),
MP.
load_table(Alias, Tab, _LoadReason, _Opts) ->
MP = get_mountpoint(Tab),
{ok, _Pid} =
mnesia_ext_sup:start_proc(
Tab, ?MODULE, start_proc, [Alias, Tab, MP]),
ok.
close_table(Alias, Tab) ->
sync_close_table(Alias, Tab).
sync_close_table(Alias, Tab) ->
try call(Alias, Tab, close_table)
catch
error:_ ->
ok
end.
index_is_consistent(Alias, Ix, Bool) ->
call(Alias, Ix, {write_info, index_consistent, Bool}).
is_index_consistent(Alias, Ix) ->
case info(Alias, Ix, index_consistent) of
undefined ->
false;
Bool when is_boolean(Bool) ->
Bool
end.
fullname(Tab, Key) ->
MP = data_mountpoint(Tab),
fullname(Tab, Key, MP).
fullname(_Tab, Key0, MP) ->
Key = if is_binary(Key0) ->
binary_to_list(Key0);
is_list(Key0) ->
lists:flatten(Key0);
is_atom(Key0) ->
list_to_binary(atom_to_list(Key0))
end,
filename:join([MP, Key]).
info(_Alias, Tab, memory) ->
try ets:info(tab_name(icache, Tab), memory)
catch
error:_ ->
0
end;
info(_Alias, Tab, Item) ->
try ets:lookup(tab_name(icache, Tab), {info,Item}) of
[{_, Value}] ->
Value;
[] ->
undefined
catch
error:Reason ->
{error, Reason}
end.
lookup(Alias, Tab, Key0) ->
Key = encode_key(Alias, Tab, Key0),
lookup(Alias, Tab, Key0, fullname(Tab, Key)).
lookup(fs_copies, _Tab, _Key, Fullname) ->
case file:read_file(Fullname) of
{ok, Bin} ->
[binary_to_term(Bin)];
{error, _} ->
[]
end;
lookup(raw_fs_copies, Tab, Key, Fullname) ->
Tag = mnesia_lib:val({Tab, record_name}),
case file:read_file(Fullname) of
{ok, Bin} ->
[{Tag, Key, Bin}];
{error, enoent} ->
[]
end.
insert(Alias, Tab, Obj) ->
call(Alias, Tab, {insert, Obj}).
%% do_insert/4 -> boolean()
%% server-side end of insert/3.
%% Returns true: new object was added; false: existing object was updated
%%
do_insert(Alias, Tab, Obj, MP) ->
Key = encode_key(Alias, Tab, element(2, Obj)),
Fullname = fullname(Tab, Key, MP),
case filelib:ensure_dir(Fullname) of
{error, _} = Err ->
Err;
ok ->
case file:read_file_info(Fullname) of
{error, enoent} ->
ok = write_object(Alias, Fullname, Obj),
true;
{ok, #file_info{type = regular}} ->
ok = write_object(Alias, Fullname, Obj),
false;
{ok, #file_info{type = directory}} ->
{error, eisdir}
end
end.
write_object(fs_copies, Fullname, Obj) ->
file:write_file(Fullname, term_to_binary(Obj, [compressed]));
write_object(raw_fs_copies, Fullname, {_, _K, V}) ->
file:write_file(Fullname, iolist_to_binary([V])).
select(Alias, Tab, Ms) ->
MP = data_mountpoint(Tab),
case do_select(Alias, Tab, MP, Ms, infinity) of
{Res, Cont} ->
'$end_of_table' = Cont(),
Res;
'$end_of_table' ->
'$end_of_table'
end.
select(Alias, Tab, Ms, Limit) when is_integer(Limit) ->
MP = data_mountpoint(Tab),
do_select(Alias, Tab, MP, Ms, Limit).
repair_continuation(Cont, _Ms) ->
Cont.
select(C) ->
Cont = get_sel_cont(C),
Cont().
get_sel_cont(C) ->
Cont = case C of
{?MODULE, C1} -> C1;
_ -> C
end,
if is_function(Cont, 0) ->
case erlang:fun_info(Cont, module) of
{_, ?MODULE} ->
Cont;
_ ->
erlang:error(badarg)
end;
true ->
erlang:error(badarg)
end.
fixtable(_Alias, _Tab, _Bool) ->
true.
delete(Alias, Tab, Key) ->
call(Alias, Tab, {delete, Key}).
do_delete(Alias, Tab, Key, MP) ->
Fullname = fullname(Tab, encode_key(Alias, Tab, Key), MP),
Deleted = case file:read_file_info(Fullname) of
{error, enoent} ->
false;
{ok, _} ->
true
end,
file:delete(Fullname),
Deleted.
match_delete(Alias, Tab, Pat) ->
MP = data_mountpoint(Tab),
Fun = fun(Obj, N) ->
Key = element(2, Obj),
case do_delete(Alias, Tab, Key, MP) of
false -> N;
true -> N+1
end
end,
Tot = fold(Alias, Tab, Fun, 0, [{Pat,[],['$_']}], 30),
call(Alias, Tab, {incr_size, -Tot}),
ok.
first(Alias, Tab) ->
MP = data_mountpoint(Tab),
Type = mnesia:table_info(Tab, type),
case list_dir(MP, Type) of
{ok, Fs} ->
case do_next1(Fs, MP, Type) of
'$end_of_table' ->
'$end_of_table';
F ->
decode_key(remove_top(MP, F), Alias, Tab)
end;
_ ->
'$end_of_table'
end.
last(Alias, Tab) ->
MP = data_mountpoint(Tab),
Type = mnesia:table_info(Tab, type),
case list_dir(MP, Type) of
{ok, Fs} ->
case do_prev1(lists:reverse(Fs), MP, Type) of
'$end_of_table' ->
'$end_of_table';
F ->
decode_key(remove_top(MP, F), Alias, Tab)
end;
_ ->
'$end_of_table'
end.
prev(Alias, Tab, Key) ->
MP = data_mountpoint(Tab),
Fullname = fullname(Tab, Key, MP),
Type = mnesia:table_info(Tab, type),
case do_prev(Fullname, Type) of
'$end_of_table' ->
'$end_of_table';
F ->
decode_key(remove_top(MP, F), Alias, Tab)
end.
next(Alias, Tab, Key0) ->
MP = data_mountpoint(Tab),
Key = encode_key(Alias, Tab, Key0),
Fullname = fullname(Tab, Key, MP),
Type = mnesia:table_info(Tab, type),
case do_next(Fullname, Type) of
'$end_of_table' ->
'$end_of_table';
F ->
decode_key(remove_top(MP, F), Alias, Tab)
end.
do_prev(Fullname, Type) ->
{Dir, Base} = get_parent(Fullname),
case list_dir(Dir, Type) of
{ok, Fs} ->
case my_lists_split(Base, Fs, rev_type(Type)) of
{_, []} ->
'$end_of_table';
{_, L} ->
do_prev1(L, Dir, Type)
end;
_ ->
%% empty, or deleted
'$end_of_table'
end.
do_next(Fullname, Type) ->
{Dir, Base} = get_parent(Fullname),
case list_dir(Dir, Type) of
{ok, Fs} ->
case my_lists_split(Base, Fs, Type) of
{_, []} ->
'$end_of_table';
{_, L} ->
do_next1(L, Dir, Type)
end;
_ ->
%% empty, or deleted
'$end_of_table'
end.
do_next1([H|T], Dir, Type) ->
File = filename:join(Dir, H),
case list_dir(File, Type) of
{ok, Fs} ->
case do_next1(Fs, File, Type) of
'$end_of_table' ->
do_next1(T, Dir, Type);
Found ->
Found
end;
{error, enotdir} ->
File
end;
do_next1([], _, _) ->
'$end_of_table'.
do_prev1([H|T], Dir, Type) ->
File = filename:join(Dir, H),
case list_dir(File, Type) of
{ok, Fs} ->
case do_prev1(lists:reverse(Fs), File, Type) of
'$end_of_table' ->
do_prev1(T, Dir, Type);
Found ->
Found
end;
{error, enotdir} ->
File
end;
do_prev1([], _, _) ->
'$end_of_table'.
get_parent(F) ->
Dir = filename:dirname(F),
Base = filename:basename(F),
{Dir, Base}.
rev_type(ordered_set) -> reverse_order;
rev_type(T) -> T.
my_lists_split(X, L, ordered_set) ->
ordered_split(X, L, []);
my_lists_split(X, L, reverse_order) ->
rev_ordered_split(X, lists:reverse(L), []);
my_lists_split(X, L, _) ->
unordered_split(X, L, []).
ordered_split(X, [H|T], Acc) when X >= H ->
ordered_split(X, T, [H|Acc]);
ordered_split(_X, L, Acc) ->
{Acc, L}.
rev_ordered_split(X, [H|T], Acc) when X =< H ->
rev_ordered_split(X, T, [H|Acc]);
rev_ordered_split(_X, L, Acc) ->
{Acc, L}.
unordered_split(X, [X|T], Acc) ->
{Acc, T};
unordered_split(X, [H|T], Acc) ->
unordered_split(X, T, [H|Acc]);
unordered_split(_X, [], Acc) ->
{Acc, []}.
slot(_Alias, _Tab, _Pos) ->
ok.
update_counter(_Alias, _Tab, _C, _Val) ->
ok.
fold(Alias, Tab, Fun, Acc, MS, N) ->
fold1(select(Alias, Tab, MS, N), Fun, Acc).
fold1('$end_of_table', _, Acc) ->
Acc;
fold1({L, Cont}, Fun, Acc) ->
fold1(select(Cont), Fun, lists:foldl(Fun, Acc, L)).
is_key_prefix(File, Fun) when is_function(Fun) ->
Fun(File);
is_key_prefix(File, {Pfx,_}) ->
lists:prefix(Pfx, File).
%% is_key_prefix1([], _) ->
%% true;
%% is_key_prefix1([H|T], [H|T1]) ->
%% is_key_prefix1(T, T1);
%% is_key_prefix1([_|_], L) when is_list(L) ->
%% false;
%% is_key_prefix1(_, '_') ->
%% true;
%% is_key_prefix1(_, V) ->
%% is_dollar_var(V).
%% is_dollar_var(P) when is_atom(P) ->
%% case atom_to_list(P) of
%% "\$" ++ T ->
%% try begin _ = list_to_integer(T),
%% true
%% end
%% catch
%% error:_ ->
%% false
%% end;
%% _ ->
%% false
%% end;
%% is_dollar_var(_) ->
%% false.
keypat(_Alias, _Dir, F) when is_function(F) ->
fun(File) -> F(keypat, File) end;
keypat(Alias, Dir, [{HeadPat,Gs,_}|_]) when is_tuple(HeadPat) ->
keypat1(Alias, HeadPat, Dir, Gs);
keypat(_, _, _) ->
{"", universal_keypat()}.
keypat1(fs_copies, HP, Dir, Gs) ->
KP = element(2, HP),
KeyVars = extract_vars(KP),
Guards = relevant_guards(Gs, KeyVars),
Pfx = Dir ++ [$/|split_key(mnesia_sext:prefix_sb32(KP))],
{Pfx, [{KP, Guards, [true]}]};
keypat1(_, HP, Dir, _) ->
case element(2, HP) of
L when is_list(L) ->
{Dir ++ [$/|plain_key_prefix(L)], [{L,[],[true]}]};
_ ->
{"", universal_keypat()}
end.
universal_keypat() ->
[{'_',[],[true]}].
plain_key_prefix([H|T]) when is_integer(H) ->
[H|plain_key_prefix(T)];
plain_key_prefix(_) ->
[].
relevant_guards(Gs, Vars) ->
case Vars -- ['_'] of
[] ->
[];
Vars1 ->
lists:filter(fun(G) ->
Vg = extract_vars(G),
intersection(Vg, Vars1) =/= []
andalso (Vg -- Vars1) == []
end, Gs)
end.
do_select(Alias, Tab, Dir, MS, Limit) ->
MP = remove_ending_slash(Dir),
Type = mnesia:table_info(Tab, type),
RecName = mnesia:table_info(Tab, record_name),
{Pfx, _} = Keypat = keypat(Alias, MP, MS),