thanks Robert for the explications. I agree with you that's the best way to remove a book is to delete the reference in ComicsCollection.
But how to do that ? Must I simply remove the reference in the ordered collection ? Voyage will syncronize automatically the data in memory with the content of the database ? Must I force the save of the data after removing the reference ? Olivier ;-) 2014-04-17 14:10 GMT+02:00 Norbert Hartl <norb...@hartl.name>: > > Am 17.04.2014 um 13:53 schrieb olivier <olivier.auver...@gmail.com>: > > > Hi, > > > > I'm using Voyage in a Pharo application. > > > > I have two MongoDB collections which are ComicsCollection and > ComicsBook. Each book is attached to a instance of ComicsCollection. The > reference of each book is stored in an ordered collection (in the instance > of ComicsCollection). The problem is that if I remove a book, the reference > to the book is not deleted from ComicsCollection. > > > > How can I remove properly a book and the reference to the book ? > > > From the smalltalk image view the problem is usually exactly the opposite: > You don’t delete objects but you remove references to them. As voyage maps > objects it is a good idea to stay in the object realm. So you should rather > remove the book from the collection. This way you won’t get errors just > garbage. The „real“ problem that arises then is that the book would still > be in the database. Just like it is in the image but there is no garbage > collector for mongo. To decide that from the image is not possible. You > load only a sub graph from the database into image memory. So you don’t > know if there are other objects referencing the book. > > If your records fit all in memory you could load all collections and books > and build the difference between all referenced books in the collections > and the total amount of books. The difference will be the set of objects > not being referenced by a collection and those can be deleted. > > If the records do not fit in memory an alternative strategy would be > needed. I started to research if it is possible to build a map/reduce based > garbage collector for common cases but got distracted. But I have the same > problem so I will need to pick it up some time. > > hope that helps, > > Norbert > > >
