[erlang-questions] Why is this delete_object giving me an error?

ryeguy <>
Mon Mar 16 15:18:00 CET 2009


Oh, so is there no way to directly delete an object using a secondary
index? ID would be my primary index, so I would have to either :
A) Get the ID and delete by that with delete() or
B) Get the whole record and delete by that with delete_object()?

Do I understand this correctly?

On Mar 16, 9:21 am, Jeroen Koops <> wrote:
> Hi,
>
> dirty_delete_object (and also delete_object) can only be used with a
> complete record - i.e. all fields must be filled in. It does not accept
> wildcard patterns.
>
> If you want to delete all user with a certain first name, you need an index
> on the first_name attribute, query for all users with that first name using
> mnesia:index_read or dirty_index_read, and finally manually delete all
> returned records with delete_object or delete.
>
> Regards,
>
> Jeroen
>
> On Mon, Mar 16, 2009 at 2:05 PM, ryeguy <> wrote:
> > I don't see what's wrong here, but I may just misunderstand the
> > syntax. I'm trying to delete a "user" record from my "user" mnesia
> > table who have the first name of "ryan" (there are multiples of them).
> > Here is what I do:
>
> > Delete=#user{first_name = "ryan", _ = '_'},
> > mnesia:dirty_delete_object(Delete)
>
> > Here is my record definition:
> > -record(user, {id,
> >                           username,
> >                           password,
> >                           email,
> >                           first_name,
> >                           last_name,
> >                           last_login, % Date/time user last logged in
> >                           reg_date}). % Date/time user registered the
> > account
>
> > And here is the exception I'm getting:
> > ** exception exit: {aborted,
> >                       {bad_type,user,
> >                           {user,'_','_','_','_',"ryan",'_','_','_'}}}
> >     in function  mnesia:abort/1
> >     in call from users:register/1
>
> > It seems like a perfect match. What could cause this problem?
>
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