aboutsummaryrefslogblamecommitdiffstats
path: root/lib/stdlib/test/ets_tough_SUITE.erl
blob: d9d0461575e2f51089971dcafbc3f1061f8c7f7b (plain) (tree)
1
2
3
4
5
6
7
8
9
10
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
                   
  
                                                        
  



                                                                      
  


                                                                         
  

                         
                                                                    
                                                          
                                                   
                       
                                                    
                                         
 
         
          


            




                         
                                     
           
                                    
           
 








                                                       
                                  



                                     
                                   


































































































































































































































                                                                          
                                    











                                                                    
                                    





















































































































































































































































































































































































































































































































































































































































































































































































































                                                                               
                                              













                                                                      
%%
%% %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%
%%
-module(ets_tough_SUITE).
-export([all/0, suite/0,groups/0,init_per_suite/1, end_per_suite/1, 
	 init_per_group/2,end_per_group/2,ex1/1]).
-export([init/1,terminate/2,handle_call/3,handle_info/2]).
-export([init_per_testcase/2, end_per_testcase/2]).
-compile([export_all]).
-include_lib("test_server/include/test_server.hrl").

suite() -> [{ct_hooks,[ts_install_cth]}].

all() -> 
    [ex1].

groups() -> 
    [].

init_per_suite(Config) ->
    Config.

end_per_suite(_Config) ->
    ok.

init_per_group(_GroupName, Config) ->
    Config.

end_per_group(_GroupName, Config) ->
    Config.



-define(DEBUG(X),debug_disabled).
%%-define(DEBUG(X),X).
-define(GLOBAL_PARAMS,ets_tough_SUITE_global_params).

init_per_testcase(_Func, Config) ->
    Dog=test_server:timetrap(test_server:seconds(300)),
    [{watchdog, Dog}|Config].

end_per_testcase(_Func, Config) ->
    Dog=?config(watchdog, Config),
    test_server:timetrap_cancel(Dog),
    ets:delete(?GLOBAL_PARAMS).


ex1(Config) when is_list(Config) ->
    ?line ets:new(?GLOBAL_PARAMS,[named_table,public]),
    ?line ets:insert(?GLOBAL_PARAMS,{a,set}),
    ?line ets:insert(?GLOBAL_PARAMS,{b,set}),
    ?line ex1_sub(Config),
    ?line ets:insert(?GLOBAL_PARAMS,{a,ordered_set}),
    ?line ets:insert(?GLOBAL_PARAMS,{b,set}),
    ?line ex1_sub(Config),
    ?line ets:insert(?GLOBAL_PARAMS,{a,ordered_set}),
    ?line ets:insert(?GLOBAL_PARAMS,{b,ordered_set}),
    ?line ex1_sub(Config).    
    
    


ex1_sub(Config) ->
    {A,B} = prep(Config),
    N = 
	case ?config(ets_tough_SUITE_iters,Config) of
	    undefined ->
		5000;
	    Other -> 
		Other
	end,
    {NewA,NewB} = run({A,B},N),
    _Gurkor = lists:keysearch(gurka,1,ets:all()),
    (catch stop(NewA)),
    (catch stop(NewB)),
    ok.

prep(Config) ->
    random:seed(),
    put(dump_ticket,none),
    DumpDir = filename:join(?config(priv_dir,Config), "ets_tough"),
    file:make_dir(DumpDir),
    put(dump_dir,DumpDir),
    process_flag(trap_exit,true),
    {ok, A} = start(a),
    {ok, B} = start(b),
    {A,B}.

run({A,B},N) ->
    run(A,B,0,N).

run(A,B,N,N) ->
    {A,B};
run(A,B,N,M) ->
    eat_msgs(),
    Op = random_operation(),
    ?DEBUG(io:format("~w: ",[N])),
    case catch operate(Op,A,B) of
	{'EXIT',Reason} ->
	    io:format("\nFAILURE on ~w: ~w, reason: ~w\n",[N,Op,Reason]),
	    exit(failed);
	{new_a,NewA} ->
	    run(NewA,B,N+1,M);
	_ ->
	    run(A,B,N+1,M)
    end.

eat_msgs() ->
    receive
	_Anything ->
	    eat_msgs()
    after 0 ->
	    ok
    end.

operate(get,A,B) ->
    case random_key() of
	1 ->
	    Class = random_class(),
	    AnsA = lists:sort(dget_class(A,Class,all)),
	    AnsB = lists:sort(dget_class(B,Class,all)),
	    ?DEBUG(io:format("get_class ~w (~w)\n",[Class,AnsA])),
	    AnsA = AnsB;
	_Other ->
	    Class = random_class(),
	    Key = random_key(),
	    AnsA = dget(A,Class,Key),
	    AnsB = dget(B,Class,Key),
	    ?DEBUG(io:format("get ~w,~w (~w)\n",[Class,Key,AnsA])),
	    AnsA = AnsB
    end;

operate(put,A,B) ->
    Class = random_class(),
    Key = random_key(),
    Value = random_value(),
    AnsA = dput(A,Class,Key,Value),
    AnsB = dput(B,Class,Key,Value),
    ?DEBUG(io:format("put ~w,~w=~w (~w)\n",[Class,Key,Value,AnsA])),
    AnsA = AnsB;

operate(erase,A,B) ->
    case random_key() of
	1 ->
	    Class = random_class(),
	    AnsA = derase_class(A,Class),
	    AnsB = derase_class(B,Class),
	    ?DEBUG(io:format("erase_class ~w\n",[Class])),
	    AnsA = AnsB;
	_Other ->
	    Class = random_class(),
	    Key = random_key(),
	    AnsA = derase(A,Class,Key),
	    AnsB = derase(B,Class,Key),
	    ?DEBUG(io:format("erase ~w,~w (~w)\n",[Class,Key,AnsA])),
	    AnsA = AnsB
    end;

operate(dirty_get,A,_B) ->
    Class = random_class(),
    Key = random_key(),
    %% only try dirty get on the b-side (which is never dumping)
    AnsA = dget(A,Class,Key),
    AnsB = dirty_dget(b,Class,Key),
    ?DEBUG(io:format("dirty_get ~w,~w (~w)\n",[Class,Key,AnsA])),
    AnsA = AnsB;

operate(dump,A,_B) ->
    case get(dump_ticket) of
	{dump_more,Ticket} ->
	    Units = random_key(),
	    NewTicket = ddump_next(A,Units,Ticket),
	    put(dump_ticket,NewTicket),
	    _Result = case NewTicket of
			 done -> done;
			 _ ->    dump_more
		     end,
	    ?DEBUG(io:format("dump ~w (~w)\n",[Units,_Result]));
	_ ->
	    DumpDir = get(dump_dir),
	    case random_key() of
		1 ->
		    ?DEBUG(io:format("start_dump\n",[])),
		    NewTicket = ddump_first(A,DumpDir),
		    put(dump_ticket,NewTicket);
		2 ->
		    ?DEBUG(io:format("dump_and_restore\n",[])),
		    {dump_more,NewTicket} = ddump_first(A,DumpDir),
		    done = ddump_next(A,1000000,NewTicket),
		    stop(A),
		    {ok, NewA} = start(a,DumpDir),
		    {new_a,NewA};
		_ ->
		    ?DEBUG(io:format("idle\n",[])),
		    ok
	    end
    end.
    
random_operation() ->
    Ops = {get,put,erase,dirty_get,dump},
    random_element(Ops).

random_class() ->
    Classes = {foo,bar,tomat,gurka},
    random_element(Classes).

random_key() ->
    random:uniform(8).

random_value() ->
    case random:uniform(5) of
	1 -> ok;
	2 -> {data,random_key()};
	3 -> {foo,bar,random_class()};
	4 -> random:uniform(1000);
	5 -> {recursive,random_value()}
    end.

random_element(T) ->
    I = random:uniform(tuple_size(T)),
    element(I,T).

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

show_table(N) ->
    FileName = ["etsdump.",integer_to_list(N)],
    case file:open(FileName,read) of
	{ok,Fd} ->
	    show_entries(Fd);
	_ ->
	    error
    end.
	    
show_entries(Fd) ->
    case phys_read_len(Fd) of
	{ok,Len} ->
	    case phys_read_entry(Fd,Len) of
		{ok,ok} ->
		    ok;
		{ok,{Key,Val}} ->
		    io:format("~w\n",[{Key,Val}]),
		    show_entries(Fd);
		_ ->
		    error
	    end;
	_ ->
	    error
    end.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%% DEFINITIONS %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

-define(NAMED_TABLES,true).
-define(DB_NAME_KEY, {'$db_name'}).
-define(LIST_OF_CLASSES_KEY,{'$list_of_classes'}).
-define(DUMPING_FLAG_KEY,{'$dumping_flag'}).
-define(DUMP_DIRECTORY_KEY,{'$dump_directory'}).
-define(ERASE_MARK(Key),{{{'$erased'},Key}}).
-define(ets_new,ets:new).
-define(ets_lookup,ets:lookup).
-define(ets_insert,ets:insert).    % erlang:db_put
-define(ets_delete,ets:delete).    % erlang:db_erase
-define(ets_first,ets:first).      % erlang:db_first
-define(ets_next,ets:next).        % erlang:db_next_key
-define(ets_info,ets:info).        % erlang:db_info

%%% INTERFACE FUNCTIONS %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%%% start(DbName) -> Pid | {error,Reason}
%%%
%%% Starts the ets table database with name DbName

start(DbName) ->
    case gen_server:start_link(ets_tough_SUITE,{DbName,no_dump_dir},[]) of
	{ok,Pid} when is_pid(Pid) ->
	    {ok, Pid};
	Other ->
	    Other
    end.

%%% start(DbName,DumpDir) -> Pid | {error,Reason}
%%%
%%% Starts the ets table database with name DbName, and reads a dump
%%% from DumpDir when it starts.

start(DbName,DumpDir) ->
    case gen_server:start_link(ets_tough_SUITE,
			       {DbName,{dump_dir,DumpDir}},[]) of
	{ok,Pid} when is_pid(Pid) ->
	    {ok, Pid};
	Other ->
	    Other
    end.

%%% stop(ServerPid) -> {'EXIT',shutdown}
%%%
%%% Shuts down the ets table database

stop(ServerPid) ->
    gen_server:call(ServerPid,stop).

%%% dget(ServerPid,Class,Key) -> {value,Value} | undefined
%%%
%%% Returns a value identified by Class,Key from the database, or
%%% 'undefined' if there is no such value.

dget(ServerPid,Class,Key) ->
    gen_server:call(ServerPid,{handle_lookup,Class,Key}).

%%% dirty_dget(DbName,Class,Key) -> {value,Value} | undefined
%%%
%%% This is looks up the value directly in the ets table
%%% to avoid message passing. Several databases may be started,
%%% so the admin table must be registered.

dirty_dget(DbName,Class,Key) ->
    Admin = admin_table_name(DbName),
    case catch(?ets_lookup(Admin,Class)) of
	[{_Class,[Tab|_Tabs]}] ->
	    case ?ets_lookup(Tab,Key) of
		[{_Key,Value}] ->
		    {value,Value};
		_ ->
		    undefined
	    end;
	_ ->
	    undefined
    end.

%%% dput(ServerPid,Class,Key,Value) -> undefined | {value,OldValue}
%%%
%%% Inserts the given Value to be identified by Class,Key. Any prevoius
%%% value is returned, or otherwise 'undefined'.

dput(ServerPid,Class,Key,Value) ->
    gen_server:call(ServerPid,{handle_insert,Class,Key,Value}).

%%% derase(ServerPid,Class,Key) -> undefined | {value,OldValue}
%%%
%%% Erases any value identified by Class,Key

derase(ServerPid,Class,Key) ->
    gen_server:call(ServerPid,{handle_delete,Class,Key}).

%%% dget_class(ServerPid,Class,Condition) -> KeyList
%%%
%%% Returns a list of keys where the instance match Condition.
%%% Condition = 'all' returns all keys in the class.
%%% The condition is supplied as Condition = {Mod, Fun, ExtraArgs},
%%% where the instance will be prepended to ExtraArgs before each
%%% call is made.

dget_class(ServerPid,Class,Condition) ->
    gen_server:call(ServerPid,
		       {handle_get_class,Class,Condition},infinity).

%%% derase_class(ServerPid,Class) -> ok
%%%
%%% Erases a whole class, identified by Class

derase_class(ServerPid,Class) ->
    gen_server:call(ServerPid,{handle_delete_class,Class}, infinity).

%%% dmodify(ServerPid,Application) -> ok
%%%
%%% Applies a function on every instance in the database.
%%% The user provided function must always return one of the
%%% terms {ok,NewItem}, true, or false.
%%% Aug 96, this is only used to reset all timestamp values
%%% in the database.
%%% The function is supplied as Application = {Mod, Fun, ExtraArgs},
%%% where the instance will be prepended to ExtraArgs before each
%%% call is made.

dmodify(ServerPid,Application) ->
    gen_server:call(ServerPid,{handle_dmodify,Application}, infinity).

%%% ddump_first(ServerPid,DumpDir) -> {dump_more,Ticket} | already_dumping
%%%
%%% Starts dumping the database. This call redirects all database updates
%%% to temporary tables, so that exactly the same database image will be
%%% written to disk as is in memory when this function is called.
%%% The returned Ticket is to be used with ddump_next/2

ddump_first(ServerPid,DumpDir) ->
    gen_server:call(ServerPid,{handle_dump_first,DumpDir}, infinity).

%%% ddump_next(ServerPid,Count,Ticket) -> {dump_more,Ticket} | done
%%%
%%% Dumps the database. This function performs Count units of dump work.
%%% Higher value of Count makes the entire dump operation more efficient,
%%% but blocks the database for longer periods of time.
%%% If there is still more work to be done, a new Ticket is returned,
%%% or 'done' otherwise.

ddump_next(ServerPid,Count,Ticket) ->
    gen_server:call(ServerPid,{handle_dump_next,Ticket,Count},150000).

%%% PRIVATE HANDLER FUNCTIONS %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%%% Admin
%%% -----
%%%
%%% The database has a main administrative table Admin. It always contains
%%% these four items:
%%%
%%%    {{'$db_name'},Name}
%%%    {{'$list_of_classes'},ListOfClasses}
%%%    {{'$dumping_flag'},BoolDumping}
%%%    {{'$dump_directory'},Dir}
%%%
%%% The ListOfClasses is simply a list of all Classes that has ever been
%%% inserted in the database. It's used to know which tables to dump.
%%% The dump flag is 'true' while dump is in progress, to make it
%%% impossible to start a new dump before an old dump is completed.
%%%
%%% For each class there is an entry of the form
%%%
%%%    {Class,ListOfTables}
%%%
%%% Where the ListOfTables is the list of class tables (see below)
%%%
%%% Class Tables
%%% ------------
%%%
%%% The class tables are common ets tables that have the actual user
%%% data stored in them.
%%%
%%% Normally there is only one class table, Mtab (main table).
%%% When dumping is initiated, each class is syncronously given a 
%%% temporary table, Ttab, where all updates are stored. Reads are 
%%% directed to the Ttab first, and only if not found there, Mtab is
%%% consulted.
%%%
%%% Writes always go to the first table in the table sequence. This
%%% ensures that the dump algorithm can enumerate the entries in the
%%% other tables, without risk of being disrupted.
%%%
%%% When the dumping to disk is completed, it's time to write back
%%% whatever updates that came into the Ttab to Mtab. To do this, a
%%% third table is needed, Utab, to handle all updates while Ttab is
%%% being copied to Mtab. When all of Ttab is copied, Ttab is thrown
%%% away, and the whole process is repeated with Utab as Ttab until
%%% eventually nobody wrote to Utab while Ttab was copied (clean run).
%%%
%%% There is no _guarantee_ that this will ever happen, but unless there
%%% is a constant (and quite high frequency) stream of updates to a
%%% particular class, this should work.
%%%
%%% (It is possible to make this failsafe, by copying the elements in
%%% Mtab to Ttab. This is probably a lot more expensive, though)
%%%
%%% Erasure during dump
%%% -------------------
%%%
%%% Erasing need special attention when a single class has several 
%%% tables. It really boils down to a number of cases:
%%% 
%%% - element does not exist in Ttab.
%%%     A special erase record is written, {{{'$erased'},Key}} which
%%%     is hopefully different from all other keys used by the user.
%%% - element exists in Ttab
%%%     The element is deleted, and erase record is written
%%% - element does not exist in Ttab, but there is an erase record
%%%     fine, do nothing
%%% - element exist in Ttab, and there is an erase record
%%%     This happens when a record is deleted from Ttab, then written
%%%     back again. Erase records are not looked for when inserting
%%%     new data (and that's not necessary)
%%%
%%% Then when Ttab should be copied to Mtab:
%%%
%%% - found an element
%%%     Usual case, just copy
%%% - found erase record
%%%     Check if there is an element with the same key as the erase
%%%     record. If so it has been written later than the erasure, so
%%%     the erasure is obsolete. Otherwise erase the record from Mtab.
%%%
%%% Delete Class
%%% ------------
%%%
%%% A slight problem is deleting an entire class while dumping is in
%%% progress. For consitency, all user visible traces of the class must
%%% be deleted, while dumping must not be affected. On top of that, the
%%% deleted class may well be recreated while dumping is still going on,
%%% and entries added.
%%%
%%% This is solved by having the dump algorithm keep track of the table
%%% identifiers of the tables to dump, rather than asking the admin table
%%% (since the class might be deleted there). The dump algorithm will
%%% itself take care of deleting the tables used in the dumping, while the
%%% normal database interface deletes the "first table", the table that is
%%% currently accepting all write operations.


init({DbName,DumpDir}) ->
    case DumpDir of
	no_dump_dir ->
	    Admin = make_admin_table(DbName),
	    ?ets_insert(Admin,{?LIST_OF_CLASSES_KEY,[]}),
	    init2(DbName,Admin);
	{dump_dir,Dir} ->
	    case load_dump(DbName,Dir) of
		{ok,Admin} ->
		    ?ets_insert(Admin,{?DUMP_DIRECTORY_KEY,Dir}),
		    init2(DbName,Admin);
		_ ->
		    cant_load_dump
	    end
    end.

init2(DbName,Admin) ->
    ?ets_insert(Admin,{?DUMPING_FLAG_KEY,false}),
    ?ets_insert(Admin,{?DB_NAME_KEY,DbName}),
    {ok, Admin}.

terminate(_Reason,_Admin) ->
    ok.

handle_call({handle_lookup,Class,Key},_From,Admin) ->
    %% Lookup tables to search in
    Reply =
	case ?ets_lookup(Admin,Class) of
	    [] ->
		undefined; %% no such class => no such record
	    [{_,TabList}] ->
		{_,Ans} = table_lookup(TabList, Key),
		Ans
	end,
    {reply,Reply,Admin};

handle_call({handle_insert,Class,Key,Value},_From,Admin) ->
    %% Lookup in which table to write
    Reply = 
	case ?ets_lookup(Admin,Class) of
	    [] ->
		%% undefined class, let's create it
		Mtab = make_db_table(db_name(Admin),Class),
		?ets_insert(Admin,{Class,[Mtab]}),
		[{_,Classes}] = ?ets_lookup(Admin,?LIST_OF_CLASSES_KEY),
		?ets_insert(Admin,{?LIST_OF_CLASSES_KEY,[Class|Classes]}),
		?ets_insert(Mtab, {Key, Value}),
		undefined;
	    [{_,[Tab|Tabs]}] ->
		{_,Old} = table_lookup([Tab|Tabs], Key),
		?ets_insert(Tab, {Key, Value}),
		Old
	end,
    {reply,Reply,Admin};

handle_call({handle_delete,Class,Key},_From,Admin) ->
    %% Lookup in which table to write
    Reply =
	case ?ets_lookup(Admin, Class) of
	    [] ->
		undefined; %% no such class, but delete is happy anyway
	    [{_,[Tab]}] ->
		%% When there is only one table, simply deleting is enough
		{_,Old} = table_lookup(Tab,Key),
		?ets_delete(Tab,Key),
		Old;
	    [{_,[Tab|Tabs]}] ->
		%% When there are more tables, we have to write a delete
		%% record into the first one, so that nobody goes looking
		%% for this entry in some other table
		{_,Old} = table_lookup([Tab|Tabs],Key),
		?ets_insert(Tab, {?ERASE_MARK(Key), erased}),
		?ets_delete(Tab,Key),
		Old
	end,
    {reply,Reply,Admin};

handle_call({handle_get_class,Class,Cond},_From,Admin) ->
    Reply =
	case ?ets_lookup(Admin,Class) of     % Lookup tables to search in
	    [] ->
		[];          % no such class
	    [{_,TabList}] ->
		table_lookup_batch(TabList, Class, Cond)  % get class data
	end,
    {reply,Reply,Admin};

handle_call({handle_delete_class,Class},_From,Admin) ->
    Reply =
	case ?ets_lookup(Admin, Class) of
	    [] ->
		ok;     % no such class, but delete_class is happy anyway
	    [{_,[Tab|_Tabs]}] ->
		%% Always delete the first table (the one we're writing into)
		%% In case we're dumping, the rest of the tables will be
		%% taken care of by the dump algorithm.
		?ets_delete(Tab),
		[{_, Classes}] = ?ets_lookup(Admin, ?LIST_OF_CLASSES_KEY),
		NewClasses = lists:delete(Class, Classes),
		?ets_insert(Admin, {?LIST_OF_CLASSES_KEY, NewClasses}),
		?ets_delete(Admin, Class),
		ok
	end,
    {reply,Reply,Admin};

handle_call({handle_dmodify,Application},_From,Admin) ->
    [{_, Classes}] = ?ets_lookup(Admin, ?LIST_OF_CLASSES_KEY),
    modify(Application, Classes, Admin),
    {reply,ok,Admin};

handle_call({handle_dump_first,DumpDir},_From,Admin) ->
    case ?ets_lookup(Admin,?DUMPING_FLAG_KEY) of
	[{_,true}] ->
	    {reply,already_dumping,Admin};
	_ ->
	    phys_remove_ok(DumpDir),
	    [{_,Classes}] = ?ets_lookup(Admin,?LIST_OF_CLASSES_KEY),
	    Tables = dump_prepare_classes(Classes,Admin),
	    ?ets_insert(Admin,{?DUMPING_FLAG_KEY,true}),
	    %% this is the new dir for dumping:
	    ?ets_insert(Admin,{?DUMP_DIRECTORY_KEY,DumpDir}),
	    handle_dump_next({[{admin,Classes}|Tables]},0,Admin)
    end;

%% All done, good work!
handle_call({handle_dump_next,Ticket,Count},_From,Admin) ->
    handle_dump_next(Ticket,Count,Admin);

handle_call(stop,_From,Admin) ->
    ?ets_delete(Admin), % Make sure table is gone before reply is sent.
    {stop, normal, ok, []}.

handle_info({'EXIT',_Pid,_Reason},Admin) ->
    {stop,normal,Admin}.

handle_delete(Class, Key, Admin) ->
    handle_call({handle_delete,Class,Key},from,Admin).

handle_insert(Class, Key, Value, Admin) ->
    handle_call({handle_insert,Class,Key,Value},from,Admin).

handle_lookup(Class, Key, Admin) ->
    handle_call({handle_lookup,Class,Key},from,Admin).


handle_dump_next({[]},_Count,Admin) ->
    [{_Key,DumpDir}] = ?ets_lookup(Admin,?DUMP_DIRECTORY_KEY),
    phys_ok_dump(DumpDir),
    ?ets_insert(Admin,{?DUMPING_FLAG_KEY,false}),
    {reply,done,Admin};

%% No more operations, return to user asking for more
handle_dump_next(Ticket,0,Admin) ->
    {reply,{dump_more,Ticket},Admin};

%% Dump the admin table. Costs one dump-work unit.
handle_dump_next({[{admin,Classes}|Tables]},Count,Admin) ->
    [{_Key,DumpDir}] = ?ets_lookup(Admin,?DUMP_DIRECTORY_KEY),
    DumpData = phys_init_dump(admin,DumpDir,0),
    phys_dump({?LIST_OF_CLASSES_KEY,Classes},DumpData),
    phys_finish_dump(DumpData),
    handle_dump_next({Tables},Count-1,Admin);

%% Pick out a class and start dumping it
handle_dump_next({[{Class,Mtab}|Tables]},Count,Admin) ->
    ?DEBUG(io:format("DUMP CLASS ~w\n",[Class])),
    [{_Key,DumpDir}] = ?ets_lookup(Admin,?DUMP_DIRECTORY_KEY),
    DumpData = phys_init_dump(Class,DumpDir,length(Tables)+1),
    First = ?ets_first(Mtab),
    handle_dump_next({Class,Tables,Mtab,First,DumpData},Count,Admin);

%% All keys in this class have been written to disk, now we have to
%% copy all items from temporary Ttab to main Mtab
handle_dump_next({Class,Tables,Stab,'$end_of_table',DumpData},Count,Admin) ->
    phys_finish_dump(DumpData),
    ?DEBUG(io:format("Cleaning up temporary table in ~p\n",[Class])),
    case ?ets_lookup(Admin,Class) of
	[{Key,[Utab,Mtab]}] ->
	    Ttab = make_db_table(db_name(Admin),Class),
	    ?ets_insert(Admin,{Key,[Ttab,Utab,Mtab]}),
	    First = ?ets_first(Utab),
	    handle_dump_next({3,Class,Tables,Utab,First,Mtab},Count,Admin);
	_Other ->
	    %% Class deleted (and maybe recreated) while dumping, no need to 
	    %% bring this one up to date. Just discard late additions.
	    ?ets_delete(Stab),
	    handle_dump_next({Tables},Count,Admin)
    end;

%% Dumping one key to disk. Costs one dump-work unit.
handle_dump_next({Class,Tables,Tab,Key,DumpData},Count,Admin) ->
    [KeyVal] = ?ets_lookup(Tab,Key),
    phys_dump(KeyVal,DumpData),
    NextKey = ?ets_next(Tab,Key),
    handle_dump_next({Class,Tables,Tab,NextKey,DumpData},Count-1,Admin);

%% Done copying elements from Ttab to Mtab
%% check if Utab is empty and go on with next class, or
%% make Utab the current Ttab, and run again
%% ... will this ever end? ;-)
handle_dump_next({3,Class,Tables,Stab,'$end_of_table',Dtab},Count,Admin) ->
    case ?ets_lookup(Admin,Class) of
	[{Key,[Ttab,Utab,Mtab]}] ->
	    case ?ets_info(Ttab,size) of
		0 ->
		    ?ets_insert(Admin,{Key,[Mtab]}),
		    ?ets_delete(Ttab),
		    ?ets_delete(Utab),
		    handle_dump_next({Tables},Count,Admin);
		_Work ->
		    ?DEBUG(io:format("Switching direction in ~p\n",[Class])),
		    %% Which is faster, deleting all the entries
		    %% in a table, or deleting it and create a new?
		    ?ets_delete(Utab),
		    Ntab = make_db_table(db_name(Admin),Class),
		    ?ets_insert(Admin,{Key,[Ntab,Ttab,Mtab]}),
		    First = ?ets_first(Ttab),
		    handle_dump_next({3,Class,Tables,Ttab,First,Mtab},
				     Count,Admin)
	    end;
	_Other ->
	    %% Class deleted (and maybe recreated) while dumping, no need to 
	    %% bring this one up to date. Just discard late additions.
	    ?ets_delete(Stab),
	    ?ets_delete(Dtab),
	    handle_dump_next({Tables},Count,Admin)
    end;

%% Copy one key from Ttab to Mtab
%% costs one dump-work unit
handle_dump_next({3,Class,Tables,Stab,Key,Dtab},Count,Admin) ->
    copy_dump_entry(Stab,Key,Dtab),
    NextKey = ?ets_next(Stab,Key),
    handle_dump_next({3,Class,Tables,Stab,NextKey,Dtab},Count-1,Admin).

%%% INTERNAL HELPER FUNCTIONS %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%%% admin_table_name(DbName) -> Name
%%%
%%% Returns the name of the admin table of the table DbName

admin_table_name(DbName) ->
    list_to_atom(lists:append(atom_to_list(DbName),"#admin")).

%%% make_admin_table(DbName) -> EtsAdminTable
%%%
%%% Creates and registers an ETS Admin table

make_admin_table(DbName) ->
    ?ets_new(admin_table_name(DbName),[named_table,protected,db_type(DbName)]).

%%% make_db_table(DbName,Name) -> EtsTable
%%%
%%% Creates an ETS database table

make_db_table(DbName, Name) ->
    ?ets_new(Name,[protected,db_type(DbName)]).

db_name(Admin) ->
    ets:lookup_element(Admin,?DB_NAME_KEY,2).

db_type(DbName) ->
    case ets:lookup(?GLOBAL_PARAMS, DbName) of
	[] ->
	    set;
	[{DbName,X}] ->
	    X
    end.

%%% table_lookup(Table,Key) -> 
%%% table_lookup(TableList,Key) ->
%%%    {def,{value,Value}} | {undef,undefined} | (erased,undefined}
%%%
%%% Looks up key in the table and returns it value, or undefined
%%% if there is no such key.
%%% If a list of tables is given, they are searched one after another
%%% for a matching key, until one is found. The search is discontinued
%%% if a record telling that the key was deleted is found.

table_lookup([], _Key) ->
    {undef,undefined};
table_lookup([Table|Tables], Key) ->
    case table_lookup(Table,Key) of
	{_,undefined} ->
	    case ?ets_lookup(Table,?ERASE_MARK(Key)) of
		[] ->
		    table_lookup(Tables,Key);
		_Definition ->
		    %% The element has been deleted, don't look further!
		    %% Pretend we never saw anything..
		    {erased,undefined}
	    end;
	Answer ->
	    Answer
    end;
table_lookup(Table, Key) ->
    case ?ets_lookup(Table,Key) of
	[] ->
	    {undef,undefined};
	[{_Key,Value}] ->
	    {def,{value,Value}}
    end.

%%% table_lookup_batch(Tables, Class, Cond) -> KeyList
%%%
%%% Extract the keys from a table or a table group.
%%% If a condition is supplied, it is on the form {Mod, Fun, ExtraArgs}
%%% and returns {true,Key} or false when called using
%%% apply(Mod, Fun, [Instance|ExtraArgs]).
%%% Instance is, for historic reasons, {{Class, Key}, Value} when the function
%%% is called. Cond = 'all' can be used to get all keys from a class.

table_lookup_batch([],_Class,_Cond) ->
    [];
table_lookup_batch([Table|Tables],Class,Cond) ->
    table_lookup_batch([],Tables,Table,ets:first(Table),Class,Cond,[]).
    
table_lookup_batch(_Passed,[],_,'$end_of_table',_Class,_Cond,Ack) ->
    Ack;
table_lookup_batch(Passed,[NewTable|Tables],Table,'$end_of_table',
		   Class,Cond,Ack) ->
    table_lookup_batch(lists:append(Passed,[Table]),Tables,
		       NewTable,ets:first(NewTable),Class,Cond,Ack);
table_lookup_batch(Passed,Tables,Table,?ERASE_MARK(Key),Class,Cond,Ack) ->
    table_lookup_batch(Passed,Tables,Table,?ets_next(Table,?ERASE_MARK(Key)),
		       Class,Cond,Ack);
    
table_lookup_batch(Passed,Tables,Table,Key,Class,Cond,Ack) ->
    NewAck =
	case table_lookup(Passed,Key) of
	    {undef,undefined} ->
		[{_Key,Value}] = ?ets_lookup(Table,Key),
		case Cond of    % are there any conditions?
		    all ->
			[Key|Ack];
		    {M, F, A} ->
			%% apply the condition test.
			%% Applications need keys to consist of
			%% {class, primkey}, so we make it that way
			case apply(M, F, [{{Class, Key}, Value}|A]) of
			    {true, Key} -> [Key|Ack];
			    false ->       Ack
			end
		end;
	    _Other -> 
		%% Already processed (or erased) key
		%% {def,{value,Value}} ->
		%% {erased,undefined} ->
		Ack
	end,
    table_lookup_batch(Passed,Tables,Table,?ets_next(Table,Key),
		       Class,Cond,NewAck).

%%% modify(Application, ClassList, Admin) -> ok.
%%%
%%% This function modifies each element of the classes

modify(_Application, [], _Admin) ->
    ok;
modify(Application, [Class|Classes], Admin) ->
    ?DEBUG(io:format("modifying class ~p\n", [Class])),
    [{_,Tables}] = ?ets_lookup(Admin, Class),
    modify_class(Application, Class, table_lookup_batch(Tables, Class, all),
		 Admin),
    modify(Application, Classes, Admin).

modify_class(_Application, _Class, [], _Admin) ->
    ok;
modify_class({Mod, Fun, ExtraArgs}, Class, [Key|Keys], Admin) ->
    {ok, {{value, Value}, _Admin}} = handle_lookup(Class, Key, Admin),
    %% The applications think that a key consists of {class, primkey},
    %% so let them.
    case apply(Mod,Fun,[{{Class, Key}, Value}|ExtraArgs]) of
	{ok,{{NewClass, NewKey}, NewValue}} ->   % The item is modified.
	    %% remove old instance, insert new
	    %% JALI could be optimized (we don't care about previous values),
	    %% but ets_delete/insert is *not* enough
	    handle_delete(Class, Key, Admin),
	    handle_insert(NewClass, NewKey, NewValue, Admin);
	true ->                           % The item should be left as it is.
	    ok;
	false ->                          % The item should be removed!
	    %% JALI could be optimized (we don't care about previous values),
	    %% but ets_delete is *not* enough
	    handle_delete(Class, Key, Admin)
    end,
    modify_class({Mod, Fun, ExtraArgs}, Class, Keys, Admin).

%%% dump_prepare_classes(Classes,Admin) -> ok
%%%
%%% Create a Ttab for each class, and insert 
%%% the new table order in Admin

dump_prepare_classes(Classes,Admin) ->
    ?DEBUG(io:format("DUMP CLASSES ~w\n",[Classes])),
    dump_prepare_classes(Classes,Admin,[]).

dump_prepare_classes([],_Admin,Ack) ->
    Ack;
dump_prepare_classes([Class|Classes],Admin,Ack) ->
    [{_Class,[Mtab]}] = ?ets_lookup(Admin,Class),
    %% Only one table => we can prepare for dumping
    %% In case there are several tables defined, dumping is
    %% already (still) in progress for this class (database inconsistent)
    Ttab = make_db_table(db_name(Admin),Class),
    ?ets_insert(Admin,{Class,[Ttab,Mtab]}),
    dump_prepare_classes(Classes,Admin,lists:append(Ack,[{Class,Mtab}])).

%%% copy_dump_entry(SourceTable,Key,DestinationTable) -> NobodyCares
%%%
%%% Copies Key from SourceTable to DestinationTable.
%%% If Key is an erase record, then the corresponding entry is deleted
%%% from DestinationTable, if it should be (see Erasure during dump, above)

copy_dump_entry(Stab,Key,Dtab) ->
    ?DEBUG(io:format("Copying key ~p\n",[Key])),
    case ?ets_lookup(Stab,Key) of
	[{?ERASE_MARK(RealKey),_}] ->
	    %% Only erase if the entry RealKey hasn't been written again
	    case ?ets_lookup(Stab,RealKey) of
		[] ->
		    %% No, it hasn't: we should delete
		    ?DEBUG(io:format("Erasing: ~p\n",[RealKey])),
		    ?ets_delete(Dtab,RealKey);
		_Definition ->
		    %% It has, don't erase. In this case the new value
		    %% has already or will soon be written to Dtab
		    ok
	    end;
	[KeyVal] ->
	    ?DEBUG(io:format("Forwarding: ~p\n",[KeyVal])),
	    ?ets_insert(Dtab,KeyVal)
    end.

%%% DUMP LOADING %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

load_dump(DbName,DumpDir) ->
    case phys_load_dump_ok(DumpDir) of
	ok ->
	    Admin = make_admin_table(DbName),
	    ?ets_insert(Admin,{?DB_NAME_KEY,DbName}),
	    case phys_load_table(DumpDir,0,Admin) of
		ok ->
		    load_dump2(DumpDir,Admin);
		Other ->
		    load_dump_failed(Admin,[]),
		    {error,{load_dump1,Other}}
	    end;
	Other ->
	    {error,{load_dump2,Other}}
    end.

load_dump2(DumpDir,Admin) ->
    case ?ets_lookup(Admin,?LIST_OF_CLASSES_KEY) of
	[{_Key,Classes}] ->
	    case load_dump_tables(DumpDir,Admin,Classes) of
		ok ->
		    {ok, Admin};
		Other ->
		    io:format("Dumping failed: ~p\n",[Other]),
		    load_dump_failed(Admin,Classes)
	    end;
	Other ->
	    io:format("Dumping failed2: ~p\n",[Other]),
	    load_dump_failed(Admin,[])
    end.

load_dump_failed(Admin,[]) ->
    ?ets_delete(Admin),
    {error,load_dump_failed};
load_dump_failed(Admin,[Class|Classes]) ->
    case ?ets_lookup(Admin,Class) of
	[{_Key,[Tab]}] ->
	    ?ets_delete(Tab);
	_ ->
	    ok
    end,
    load_dump_failed(Admin,Classes).

load_dump_tables(_DumpDir,_Admin,[]) ->
    ok;
load_dump_tables(DumpDir,Admin,[Class|Classes]) ->
    Mtab = make_db_table(db_name(Admin),Class),
    ?ets_insert(Admin,{Class,[Mtab]}),
    Num = length(Classes)+1,
    case phys_load_table(DumpDir,Num,Mtab) of
	ok ->
	    load_dump_tables(DumpDir,Admin,Classes);
	Other ->
	    {error,{load_dump_failed,Other}}
    end.

%%% FILE ACCESS LAYER %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%%% phys_init_dump(Class,DumpDir) -> DumpData

phys_init_dump(Class,DumpDir,Num) ->
    ?DEBUG(io:format("Opened ~p for writing\n",[Class])),
    FileName = [DumpDir,"/etsdump.",integer_to_list(Num)],
    {tag1,{ok,Fd}} = {tag1,file:open(FileName,write)},
    {Class,Fd}.

%%% phys_finish_dump(DumpData) -> NobodyCares

phys_finish_dump({_Class,Fd}) ->
    ?DEBUG(io:format("Closed ~p\n",[_Class])),
    phys_dump_term(Fd,ok),
    file:close(Fd), % JALI: OTP P1D returns true instead of ok, so no check
    ok.

%%% phys_dump(KeyVal,DumpData) -> NobodyCares

phys_dump({Key,Val},{_Class,Fd}) ->
    ?DEBUG(io:format("To disk (~p.dump): {~p,~p}\n",[_Class,Key,Val])),
    phys_dump_term(Fd,{Key,Val}),
    ok.

phys_dump_term(Fd,Term) ->
    Bin = binary_to_list(term_to_binary(Term)),
    {tag2,ok} = {tag2,io:put_chars(Fd,encode32(length(Bin)))},
    {tag3,ok} = {tag3,io:put_chars(Fd,Bin)}.

%%% phys_ok_dump(DumpDir) -> NobodyCares

phys_ok_dump(DumpDir) ->
    ?DEBUG(io:format("Ok:ing dump dir ~s\n",[DumpDir])),
    FileName = [DumpDir,"/ok"],
    {tag4,{ok,Fd}} = {tag4,file:open(FileName,write)},
    {tag5,ok} = {tag5,io:format(Fd,"ok.\n",[])},
    file:close(Fd), % JALI: OTP P1D returns true instead of ok, so no check
    ok.

phys_remove_ok(DumpDir) ->
    ?DEBUG(io:format("Removing any Ok in dump dir ~s\n",[DumpDir])),
    FileName = [DumpDir,"/ok"],
    %% don't care if delete returns ok, file probably doesn't exist
    file:delete(FileName),
    ok.

phys_load_dump_ok(DumpDir) ->
    FileName = [DumpDir,"/ok"],
    case file:consult(FileName) of
	{ok,[ok]} ->
	    ok;
	Other ->
	    {error,{consult_error,Other}}
    end.

phys_load_table(DumpDir,N,Tab) ->
    ?DEBUG(io:format("LOAD TABLE ~w\n",[N])),
    FileName = [DumpDir,"/etsdump.",integer_to_list(N)],
    case file:open(FileName,read) of
	{ok,Fd} ->
	    phys_load_entries(Fd,Tab);
	Other ->
	    {error,{open_error,Other}}
    end.
	    
phys_load_entries(Fd,Tab) ->
    case phys_read_len(Fd) of
	{ok,Len} ->
	    case phys_read_entry(Fd,Len) of
		{ok,ok} ->
		    ok;
		{ok,{Key,Val}} ->
		    ?ets_insert(Tab,{Key,Val}),
		    phys_load_entries(Fd,Tab);
		Other ->
		    {error,{read_len,Other}}
	    end;
	Other ->
	    {error,{read_len2,Other}}
    end.

phys_read_len(Fd) ->
    case io:get_chars(Fd,'',4) of
	[A,B,C,D] ->
	    {ok,decode32(A,B,C,D)};
	Other ->
	    {error,{decode,Other}}
    end.

phys_read_entry(Fd,Len) ->
    case io:get_chars(Fd,'',Len) of
	L when is_list(L), length(L) == Len ->
	    {ok,binary_to_term(list_to_binary(L))};
	Other ->
	    {error,{read_term,Other}}
    end.

encode32(N) ->
    [(N bsr 24) band 255, 
     (N bsr 16) band 255, 
     (N bsr 8) band 255,
     N band 255].

decode32(A,B,C,D) ->
    (A bsl 24) bor (B bsl 16) bor (C bsl 8) bor D.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%