%%
%% %CopyrightBegin%
%%
%% Copyright Ericsson AB 1996-2011. 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: Handles index functionality in mnesia
-module(mnesia_index).
-export([read/5,
add_index/5,
delete_index/3,
del_object_index/5,
clear_index/4,
dirty_match_object/3,
dirty_select/3,
dirty_read/3,
dirty_read2/3,
db_put/2,
db_get/2,
db_match_erase/2,
get_index_table/2,
get_index_table/3,
tab2filename/2,
tab2tmp_filename/2,
init_index/2,
init_indecies/3,
del_transient/2,
del_transient/3,
del_index_table/3]).
-import(mnesia_lib, [verbose/2]).
-include("mnesia.hrl").
-record(index, {setorbag, pos_list}).
val(Var) ->
case ?catch_val(Var) of
{'EXIT', _ReASoN_} -> mnesia_lib:other_val(Var, _ReASoN_);
_VaLuE_ -> _VaLuE_
end.
%% read an object list throuh its index table
%% we assume that table Tab has index on attribute number Pos
read(Tid, Store, Tab, IxKey, Pos) ->
ResList = mnesia_locker:ixrlock(Tid, Store, Tab, IxKey, Pos),
%% Remove all tuples which don't include Ixkey, happens when Tab is a bag
case val({Tab, setorbag}) of
bag ->
mnesia_lib:key_search_all(IxKey, Pos, ResList);
_ ->
ResList
end.
add_index(Index, Tab, Key, Obj, Old) ->
add_index2(Index#index.pos_list, Index#index.setorbag, Tab, Key, Obj, Old).
add_index2([{Pos, Ixt} |Tail], bag, Tab, K, Obj, OldRecs) ->
db_put(Ixt, {element(Pos, Obj), K}),
add_index2(Tail, bag, Tab, K, Obj, OldRecs);
add_index2([{Pos, Ixt} |Tail], Type, Tab, K, Obj, OldRecs) ->
%% Remove old tuples in index if Tab is updated
case OldRecs of
undefined ->
Old = mnesia_lib:db_get(Tab, K),
del_ixes(Ixt, Old, Pos, K);
Old ->
del_ixes(Ixt, Old, Pos, K)
end,
db_put(Ixt, {element(Pos, Obj), K}),
add_index2(Tail, Type, Tab, K, Obj, OldRecs);
add_index2([], _, _Tab, _K, _Obj, _) -> ok.
delete_index(Index, Tab, K) ->
delete_index2(Index#index.pos_list, Tab, K).
delete_index2([{Pos, Ixt} | Tail], Tab, K) ->
DelObjs = mnesia_lib:db_get(Tab, K),
del_ixes(Ixt, DelObjs, Pos, K),
delete_index2(Tail, Tab, K);
delete_index2([], _Tab, _K) -> ok.
del_ixes(_Ixt, [], _Pos, _L) -> ok;
del_ixes(Ixt, [Obj | Tail], Pos, Key) ->
db_match_erase(Ixt, {element(Pos, Obj), Key}),
del_ixes(Ixt, Tail, Pos, Key).
del_object_index(Index, Tab, K, Obj, Old) ->
del_object_index2(Index#index.pos_list, Index#index.setorbag, Tab, K, Obj, Old).
del_object_index2([], _, _Tab, _K, _Obj, _Old) -> ok;
del_object_index2([{Pos, Ixt} | Tail], SoB, Tab, K, Obj, Old) ->
case SoB of
bag ->
del_object_bag(Tab, K, Obj, Pos, Ixt, Old);
_ -> %% If set remove the tuple in index table
del_ixes(Ixt, [Obj], Pos, K)
end,
del_object_index2(Tail, SoB, Tab, K, Obj, Old).
del_object_bag(Tab, Key, Obj, Pos, Ixt, undefined) ->
IxKey = element(Pos, Obj),
Old = [X || X <- mnesia_lib:db_get(Tab, Key), element(Pos, X) =:= IxKey],
del_object_bag(Tab, Key, Obj, Pos, Ixt, Old);
%% If Tab type is bag we need remove index identifier if Tab
%% contains less than 2 elements.
del_object_bag(_Tab, Key, Obj, Pos, Ixt, Old) when length(Old) < 2 ->
del_ixes(Ixt, [Obj], Pos, Key);
del_object_bag(_Tab, _Key, _Obj, _Pos, _Ixt, _Old) -> ok.
clear_index(Index, Tab, K, Obj) ->
clear_index2(Index#index.pos_list, Tab, K, Obj).
clear_index2([], _Tab, _K, _Obj) -> ok;
clear_index2([{_Pos, Ixt} | Tail], Tab, K, Obj) ->
db_match_erase(Ixt, Obj),
clear_index2(Tail, Tab, K, Obj).
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
dirty_match_object(Tab, Pat, Pos) ->
%% Assume that we are on the node where the replica is
case element(2, Pat) of
'_' ->
IxKey = element(Pos, Pat),
RealKeys = realkeys(Tab, Pos, IxKey),
merge(RealKeys, Tab, Pat, []);
_Else ->
mnesia_lib:db_match_object(Tab, Pat)
end.
merge([{_IxKey, RealKey} | Tail], Tab, Pat, Ack) ->
%% Assume that we are on the node where the replica is
Pat2 = setelement(2, Pat, RealKey),
Recs = mnesia_lib:db_match_object(Tab, Pat2),
merge(Tail, Tab, Pat, Recs ++ Ack);
merge([], _, _, Ack) ->
Ack.
realkeys(Tab, Pos, IxKey) ->
Index = get_index_table(Tab, Pos),
db_get(Index, IxKey). % a list on the form [{IxKey, RealKey1} , ....
dirty_select(Tab, Spec, Pos) ->
%% Assume that we are on the node where the replica is
%% Returns the records without applying the match spec
%% The actual filtering is handled by the caller
IxKey = element(Pos, Spec),
RealKeys = realkeys(Tab, Pos, IxKey),
StorageType = val({Tab, storage_type}),
lists:append([mnesia_lib:db_get(StorageType, Tab, Key) || {_,Key} <- RealKeys]).
dirty_read(Tab, IxKey, Pos) ->
ResList = mnesia:dirty_rpc(Tab, ?MODULE, dirty_read2,
[Tab, IxKey, Pos]),
case val({Tab, setorbag}) of
bag ->
%% Remove all tuples which don't include Ixkey
mnesia_lib:key_search_all(IxKey, Pos, ResList);
_ ->
ResList
end.
dirty_read2(Tab, IxKey, Pos) ->
Ix = get_index_table(Tab, Pos),
Keys = db_match(Ix, {IxKey, '$1'}),
r_keys(Keys, Tab, []).
r_keys([[H]|T],Tab,Ack) ->
V = mnesia_lib:db_get(Tab, H),
r_keys(T, Tab, V ++ Ack);
r_keys([], _, Ack) ->
Ack.
%%%%%%% Creation, Init and deletion routines for index tables
%% We can have several indexes on the same table
%% this can be a fairly costly operation if table is *very* large
tab2filename(Tab, Pos) ->
mnesia_lib:dir(Tab) ++ "_" ++ integer_to_list(Pos) ++ ".DAT".
tab2tmp_filename(Tab, Pos) ->
mnesia_lib:dir(Tab) ++ "_" ++ integer_to_list(Pos) ++ ".TMP".
init_index(Tab, Storage) ->
PosList = val({Tab, index}),
init_indecies(Tab, Storage, PosList).
init_indecies(Tab, Storage, PosList) ->
case Storage of
unknown ->
ignore;
disc_only_copies ->
init_disc_index(Tab, PosList);
ram_copies ->
make_ram_index(Tab, PosList);
disc_copies ->
make_ram_index(Tab, PosList)
end.
%% works for both ram and disc indexes
del_index_table(_, unknown, _) ->
ignore;
del_index_table(Tab, Storage, Pos) ->
delete_transient_index(Tab, Pos, Storage),
mnesia_lib:del({Tab, index}, Pos).
del_transient(Tab, Storage) ->
PosList = val({Tab, index}),
del_transient(Tab, PosList, Storage).
del_transient(_, [], _) -> done;
del_transient(Tab, [Pos | Tail], Storage) ->
delete_transient_index(Tab, Pos, Storage),
del_transient(Tab, Tail, Storage).
delete_transient_index(Tab, Pos, disc_only_copies) ->
Tag = {Tab, index, Pos},
mnesia_monitor:unsafe_close_dets(Tag),
file:delete(tab2filename(Tab, Pos)),
del_index_info(Tab, Pos), %% Uses val(..)
mnesia_lib:unset({Tab, {index, Pos}});
delete_transient_index(Tab, Pos, _Storage) ->
Ixt = val({Tab, {index, Pos}}),
?ets_delete_table(Ixt),
del_index_info(Tab, Pos),
mnesia_lib:unset({Tab, {index, Pos}}).
%%%%% misc functions for the index create/init/delete functions above
%% assuming that the file exists.
init_disc_index(_Tab, []) ->
done;
init_disc_index(Tab, [Pos | Tail]) when is_integer(Pos) ->
Fn = tab2filename(Tab, Pos),
IxTag = {Tab, index, Pos},
file:delete(Fn),
Args = [{file, Fn}, {keypos, 1}, {type, bag}],
mnesia_monitor:open_dets(IxTag, Args),
Storage = disc_only_copies,
Key = mnesia_lib:db_first(Storage, Tab),
Recs = mnesia_lib:db_get(Storage, Tab, Key),
BinSize = size(term_to_binary(Recs)),
KeysPerChunk = (4000 div BinSize) + 1,
Init = {start, KeysPerChunk},
mnesia_lib:db_fixtable(Storage, Tab, true),
ok = dets:init_table(IxTag, create_fun(Init, Tab, Pos)),
mnesia_lib:db_fixtable(Storage, Tab, false),
mnesia_lib:set({Tab, {index, Pos}}, IxTag),
add_index_info(Tab, val({Tab, setorbag}), {Pos, {dets, IxTag}}),
init_disc_index(Tab, Tail).
create_fun(Cont, Tab, Pos) ->
fun(read) ->
Data =
case Cont of
{start, KeysPerChunk} ->
mnesia_lib:db_init_chunk(disc_only_copies, Tab, KeysPerChunk);
'$end_of_table' ->
'$end_of_table';
_Else ->
mnesia_lib:db_chunk(disc_only_copies, Cont)
end,
case Data of
'$end_of_table' ->
end_of_input;
{Recs, Next} ->
IdxElems = [{element(Pos, Obj), element(2, Obj)} || Obj <- Recs],
{IdxElems, create_fun(Next, Tab, Pos)}
end;
(close) ->
ok
end.
make_ram_index(_, []) ->
done;
make_ram_index(Tab, [Pos | Tail]) ->
add_ram_index(Tab, Pos),
make_ram_index(Tab, Tail).
add_ram_index(Tab, Pos) when is_integer(Pos) ->
verbose("Creating index for ~w ~n", [Tab]),
Index = mnesia_monitor:mktab(mnesia_index, [bag, public]),
Insert = fun(Rec, _Acc) ->
true = ?ets_insert(Index, {element(Pos, Rec), element(2, Rec)})
end,
mnesia_lib:db_fixtable(ram_copies, Tab, true),
true = ets:foldl(Insert, true, Tab),
mnesia_lib:db_fixtable(ram_copies, Tab, false),
mnesia_lib:set({Tab, {index, Pos}}, Index),
add_index_info(Tab, val({Tab, setorbag}), {Pos, {ram, Index}});
add_ram_index(_Tab, snmp) ->
ok.
add_index_info(Tab, Type, IxElem) ->
Commit = val({Tab, commit_work}),
case lists:keysearch(index, 1, Commit) of
false ->
Index = #index{setorbag = Type,
pos_list = [IxElem]},
%% Check later if mnesia_tm is sensative about the order
mnesia_lib:set({Tab, commit_work},
mnesia_lib:sort_commit([Index | Commit]));
{value, Old} ->
%% We could check for consistency here
Index = Old#index{pos_list = [IxElem | Old#index.pos_list]},
NewC = lists:keyreplace(index, 1, Commit, Index),
mnesia_lib:set({Tab, commit_work},
mnesia_lib:sort_commit(NewC))
end.
del_index_info(Tab, Pos) ->
Commit = val({Tab, commit_work}),
case lists:keysearch(index, 1, Commit) of
false ->
%% Something is wrong ignore
skip;
{value, Old} ->
case lists:keydelete(Pos, 1, Old#index.pos_list) of
[] ->
NewC = lists:keydelete(index, 1, Commit),
mnesia_lib:set({Tab, commit_work},
mnesia_lib:sort_commit(NewC));
New ->
Index = Old#index{pos_list = New},
NewC = lists:keyreplace(index, 1, Commit, Index),
mnesia_lib:set({Tab, commit_work},
mnesia_lib:sort_commit(NewC))
end
end.
db_put({ram, Ixt}, V) ->
true = ?ets_insert(Ixt, V);
db_put({dets, Ixt}, V) ->
ok = dets:insert(Ixt, V).
db_get({ram, Ixt}, K) ->
?ets_lookup(Ixt, K);
db_get({dets, Ixt}, K) ->
dets:lookup(Ixt, K).
db_match_erase({ram, Ixt}, Pat) ->
true = ?ets_match_delete(Ixt, Pat);
db_match_erase({dets, Ixt}, Pat) ->
ok = dets:match_delete(Ixt, Pat).
db_match({ram, Ixt}, Pat) ->
?ets_match(Ixt, Pat);
db_match({dets, Ixt}, Pat) ->
dets:match(Ixt, Pat).
get_index_table(Tab, Pos) ->
get_index_table(Tab, val({Tab, storage_type}), Pos).
get_index_table(Tab, ram_copies, Pos) ->
{ram, val({Tab, {index, Pos}})};
get_index_table(Tab, disc_copies, Pos) ->
{ram, val({Tab, {index, Pos}})};
get_index_table(Tab, disc_only_copies, Pos) ->
{dets, val({Tab, {index, Pos}})};
get_index_table(_Tab, unknown, _Pos) ->
unknown.
