Did you created the M:N relationship using the modeler or you created it 
manually ?

These are tricky to correctly configure.

Your situation may be caused by an improper flattened relationship settings. 
The flattened relationships should have nothing checked in the Advanced pane of 
the modeler.

On my models, I always create them with the modeler and the relationships to 
the inner entity does not have "own relationship" checked but have the 
"Propagate primary key" checked.


> Le 20 sept. 2016 à 14:50, o...@ocs.cz a écrit :
> Hello there,
> I have a pretty common setup: entities User and DataBlock, an M:N 
> relationship represented by an intermediate entity containing just the two 
> keys, flattened on both sides. At both sides the relationships are 
> appropriately flattened. Set to own destination+delete rule cascade.
> The problem is, upon inserting a new DataBlock and its relationship to a 
> current user, beside the two objects which should be inserted (the new 
> DataBlock and the new relationship), relationships to other (old) DataBlocks, 
> which were before simply _fetched_ for the current user (just to display the 
> current state), get inserted too — which, of course, causes an integrity 
> constraint violation “this PK already exists“.
> My code looks essentially like this:
> ===
> EOEditingContext ec= ...
> DBDataBlock ndb=new DBDataBlock()
> ec.insertObject(ndb)
> ndb.addObjectToBothSidesOfRelationshipWithKey(currentUser,'dataBlockUsers')
> // logs here, see below
> ec.saveChanges()
> ===
> Immediately before ec.saveChanges(), I log out
> (a) ec.insertedObjects(), which contains only one object (I have overridden 
> toString() to get the PK /and other attributes, removed here for conciseness/ 
> of an EO):
> [<DBDataBlock@79adaefa PK:null>]
> this is all right, null PK means a newly added object, it's the very 'ndb' 
> datablock I just have inserted and which I am now saving.
> (b) contents of the flattened M:N relationship 'ndb.dataBlockUsers' from the 
> DBDataBlock@79adaefa to DBUser, which looks like this:
> [<DBUser@71b29988 PK:1000005>]
> again, quite all right: only one related user, the currentUser which I have 
> just added to the relationship.
> (c) contents of the flattened M:N inverse relationship from the current user, 
> which looks like this:
> [<DBDataBlock@189f083a PK:1000003>, <DBDataBlock@1b47d247 PK:1000016>, 
> <DBDataBlock@5f927095 PK:1000019>, <DBDataBlock@54edfe4c PK:1000022>, 
> <DBDataBlock@35e1e59c PK:1000023>, <DBDataBlock@793b3d6d PK:1000024>, 
> <DBDataBlock@7b06dee8 PK:1000029>, <DBDataBlock@2550aab9 PK:1000033>, 
> <DBDataBlock@79adaefa PK:null>]
> for the third time, all right: 8 of them previously fetched, already existing 
> relationships to other (old) datablocks for the current user, plus one new 
> relationship to the newly added DBDataBlock@79adaefa. Perfect so far.
> At this moment, ec.saveChanges is performed. I log the database operations 
> from databaseContextWillPerformAdaptorOperations delegate method, and it 
> looks like this:
> ===
> -IN-adaptorOps === SPC: about to perform 10 DB operations     |19:54:37.061 
> 20.9.16|WorkerThread1
>               - 1: INSERT on 'DBDataBlock'  1{uid:1000042}
>               - 2: INSERT on 'DB_UserDataBlock'  2{db_id:1000023, 
> user_id:1000005}
>               - 3: INSERT on 'DB_UserDataBlock'  2{db_id:1000022, 
> user_id:1000005}
>               - 4: INSERT on 'DB_UserDataBlock'  2{db_id:1000003, 
> user_id:1000005}
>               - 5: INSERT on 'DB_UserDataBlock'  2{db_id:1000016, 
> user_id:1000005}
>               - 6: INSERT on 'DB_UserDataBlock'  2{db_id:1000042, 
> user_id:1000005}
>               - 7: INSERT on 'DB_UserDataBlock'  2{db_id:1000019, 
> user_id:1000005}
>               - 8: INSERT on 'DB_UserDataBlock'  2{db_id:1000029, 
> user_id:1000005}
>               - 9: INSERT on 'DB_UserDataBlock'  2{db_id:1000024, 
> user_id:1000005}
>               - 10: INSERT on 'DB_UserDataBlock'  2{db_id:1000033, 
> user_id:1000005}
> ===
> i.e., along with inserting the two new objects (1: the new datablock, 6: the 
> new relationship), EOF for some darned reason decides to insert _also_ all 
> those relationship objects it _fetched_ before! Of course, since they were 
> fetched, they already exist in the database, and thus cause an integrity 
> constraint violation “this PK already exists“.
> Well, logging out 
> "currentUser.editingContext().committedSnapshotForObject(currentUser)['userDataBlock']"
>  before saveChanges, I get an empty array. I must admit I don't know whether 
> there should be the relationship objects in this snapshot, but anyway:
> - if not, I have no idea where to find the culprit;
> - if yes, well, the culprit of those inserts is explained, but why on earth 
> the snapshot is not properly maintained by EOF?!?
> Any idea what might be the culprit, or at least, how to find it? I am afraid 
> I am rather out of ideas :/
> Thanks a lot,
> OC
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