Norbert, Sorry for my mistake ;-)
2014-04-17 15:18 GMT+02:00 Norbert Hartl <norb...@hartl.name>: > > Am 17.04.2014 um 15:05 schrieb olivier auverlot < > olivier.auver...@gmail.com>: > > thanks Robert for the explications. > > It’s Norbert btw. :) > > 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 ? > > You need to explicitly save it as we don’t have something like write > barriers in the image. So > > aComicCollection > removeBook: aBook; > save > > is needed. > > Norbert > > 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 >> >> >> > >
