Mnesia question

Hakan Mattsson <>
Mon Apr 26 09:00:05 CEST 1999


mikl>I suspect a misconfiguration, but I did not see what I a missing.

I think that you forgot to start the mnemosyne application.

The attached example worked for me, when Mnemosyne was started.

    ~> erl
    Erlang (BEAM) emulator version 4.8.1
     
    Eshell V4.8.1  (abort with ^G)
    1> c(memo().
    ** 1: syntax error before: '.' **
    1> c(memo). 
    ./memo.erl:27: Warning: non-recommended option 'export_all' used
    {ok,memo}
    2> memo:init().
    ok
    3> memo:task(hakan).       
    {atomic,[{tasks,drink_coffee,hakan}]}
    4> application:stop(mnemosyne).
     
    =INFO REPORT==== 26-Apr-1999::08:54:17 ===
	application: mnemosyne
	exited: stopped
	type: temporary
    ok
    5> memo:task(hakan).           
     
    =ERROR REPORT==== 26-Apr-1999::08:54:19 ===
    <0.25.0> error: nocatch in mnemosyne_lc:the_query/1
    ** exited: nocatch **
    
Regards

	Håkan
-------------------------------------+------------------------------------
Håkan Mattsson,                   | +46 8 719 9452
Computer Science Laboratory          | 
Ericsson Network Core Products       | http://www.ericsson.se/cslab/~hakan
Box 1505, SE-126 25 Stockholm Sweden |
-------------- next part --------------
-module(memo).
-author('').

-compile([export_all, {parse_transform, mnemosyne}]).

-record(tasks, {id, user_id}).
-record(users, {id, phone}).

init() ->
    ok = application:start(mnesia),
    ok = application:start(mnemosyne),
    {atomic, ok} = mnesia:create_table(tasks, [{attributes, [id, user_id]}]),
    {atomic, ok} = mnesia:create_table(users, [{attributes, [id, phone]}]),
    ok = mnesia:dirty_write(users, #users{id = hakan, phone = 99251}),
    ok = mnesia:dirty_write(tasks, #tasks{id = drink_coffee, user_id = hakan}).

task(User) ->
   Q = query 
         [ T ||
               T <- table(tasks), 
               U <- table(users),
               U.id = User,
               T.user_id = U.id ]
       end,
   F = fun() -> mnemosyne:eval(Q) end,
   mnesia:transaction(F).


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