esteban
you should do a pass on the voyage documentation chapter and add this
kind of infomration.
We can pair write if you want.
stef
On 17/4/14 17:56, Esteban Lorenzano wrote:
On 17 Apr 2014, at 15:18, Norbert Hartl <norb...@hartl.name
<mailto:norb...@hartl.name>> wrote:
Am 17.04.2014 um 15:05 schrieb olivier auverlot
<olivier.auver...@gmail.com <mailto: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.
yes, and also (if you want to be clean):
aBook remove.
(assuming aBook is also persistent).
But as Sabina points: #enableMissingContent in CommicCollection will
help you to simplify things, then you just need: "aBook remove", and
next time you read aComicCollection it will “clean” the invalid
reference.
I call that “eventual integrity” :P
but beware of it… is considered “power voyage programming” :)
Esteban
Norbert
Olivier ;-)
2014-04-17 14:10 GMT+02:00 Norbert Hartl <norb...@hartl.name
<mailto:norb...@hartl.name>>:
Am 17.04.2014 um 13:53 schrieb olivier
<olivier.auver...@gmail.com <mailto: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
