Problems with mnemosyne

[Samuel Rivas]

On Fri, 11 Apr 2003, 10:07 +0200, Dan Gudmundsson wrote:
> 
> Can you post the record definitions and the
> mnemosyne query.
> 
Of course:


The records:
-----------

-record(movie,
        {id,
	 file,
	 genre_id,
	 year,
	 new = true
	}).

-record(movie_info,
	{movie_id,          %% References movie.id
	 lang_id,
	 synopsys,
	 title
	}).

-record(shown_movie,
	{set_top_box_id, 
	 name,             %% User name
	 movie_id
	}).
	
Table creation functions:
------------------------

init_movie() ->
    {atomic, ok} = mnesia:create_table(movie,
                                       [{disc_copies, [node()]},
                                        {attributes,  record_info(fields, movie)}]).

init_movie_info() ->
    {atomic, ok} = mnesia:create_table(movie_info,
                                       [{disc_copies, [node()]},
                                        {type, bag},
                                        {index, [lang_id]},
					{attributes, record_info(fields, movie_info)}]).

init_shown_movie() ->
    {atomic, ok} = mnesia:create_table(shown_movie,
                                       [{disc_copies, [node()]},
				        {type, bag},
					{index, [name]},
					{attributes, record_info(fields, shown_movie)}]).

And the query:
-------------

get_shown_movies(LangId, StpbxId, User, GenreId) when list(LangId),
                                                      list(StpbxId),
                                                      record(User, user),
                                                      atom(GenreId) ->

    Q = query
            [{M, MI}  || M <- table(movie),
                         MI <- table(movie_info),
                         ShownMovie <- table(shown_movie),
                         M.genre_id = GenreId,
                         MI.movie_id = M.id,
                         MI.lang_id = LangId,
                         ShownMovie.set_top_box_id = StpxId,
                         ShownMovie.name = User#user.name,
                         ShownMovie.movie_id = M.id]
       end,
   F = fun() ->
               mnemosyne:eval(Q)
       end,
   mnesia:transaction(F).


I've solved the problem grouping the table keys on a single tuple,
{set_top_box_id, name} and {movie_id, lang_id} for both 
shown_movie and movie_info tables. This elimates the needed to
add extra indices.

Regards

-- 
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|	Samuel        |
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