Mnesia odd behaviour - delete_object

Martin Bjorklund mbj@REDACTED
Tue Oct 30 20:20:27 CET 2001

Dan Gudmundsson <dgud@REDACTED> wrote:
> Hi 
> A explanation of the implementation, then you can argument about
> semantics :-)
> mnesia:delete_object({a, key, [1]}) deletes the object if 
> and only if exactly that object exists in the database.
> So a mnesia:transaction(fun() -> mnesia:delete_object({a, key, [1]}) end)
> will not delete the object {a, key, [1,2]} since they are not the same.
> And since transactions doesn't directly operate on the tables, (not 
> until the transaction commits), this happens.
> Thus when you over write the {a, key, [1]} in your transaction, 
> you transaction view shows you the only record in the {a, key, [1]},
> and you delete that. This DELETES the WRITE operation you just did.
> And when the transaction commits, it tries to delete exactly the object 
> {a, key, [1]} from table, which doesn't exist and you are left with 
> you old value.

Yes, I understand that this is how it's implemented.  The question is
whether this is by design or accident :)  What do you say Hakan?

The more I think about it, the more I think the current behaviour is


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