[hibernate-dev] [OGM] @JoinColumns, @EmbeddedId & IN_ENTITY mode

[Emmanuel Bernard]

Let me investigate this further first. Ideally the engine would use the right column names ie the fk and not the ones from the entity ids. 
I must have messed up when I fixed the bug I discussed with you. 

On 24 sept. 2012, at 20:20, Guillaume SCHEIBEL <guillaume.scheibel at gmail.com> wrote:

> Hi guys,
> 
> I'm working on OGM-236 which consists to use by default the IN_ENTITY mode
> for association storage strategy instead of COLLECTION.
> I've just found out a little issue, when we use @JoinColumns over a
> @OneToMany property to map an @EmbeddedID with the IN_ENTITY mode, the
> navigation information are not stored directly into the document itself but
> another document composed by the join columns as the _id and the navigation
> information (in that case the IDs that the entity is related to).
> 
> Concretely, let's starting from this mapping:
> https://github.com/hibernate/hibernate-ogm/blob/master/hibernate-ogm-core/src/test/java/org/hibernate/ogm/test/id/Label.java
> https://github.com/hibernate/hibernate-ogm/blob/master/hibernate-ogm-core/src/test/java/org/hibernate/ogm/test/id/News.java
> https://github.com/hibernate/hibernate-ogm/blob/master/hibernate-ogm-core/src/test/java/org/hibernate/ogm/test/id/NewsID.java
> 
> and run this test with the IN_ENTITY mode on (to make the switch, a
> modification into MongoDBDatastoreProvider.configure() is needed)
> https://github.com/hibernate/hibernate-ogm/blob/master/hibernate-ogm-core/src/test/java/org/hibernate/ogm/test/id/CompositeIdTest.java
> 
> 
> We can expect to have something like:
> 
> {
>    "_id": {
>        "author": "Guillaume",
>        "title": "There are more than 20 JUGs in France"
>    },
>   "content": "Great! Congratulations folks",
>    "labels": [
> 
>        { "id": NumberLong(5) }
> 
> ]
> 
> }
> 
> It means this News is related to 1 Label of which ID is 5.
> But due to @JoinColumns we got this (both documents are from the News
> collection):
> 
> {
>    "_id": {
>        "author": "Guillaume",
>        "title": "There are more than 20 JUGs in France"
>    },
>    "content": "Great! Congratulations folks",
>    "labels": []
> } {
>    "_id": {
>        "news_author_fk": "Guillaume",
>        "news_topic_fk": "There are more than 20 JUGs in France"
>    },
>    "labels": [{
>        "id": NumberLong(5)
>    }]
> }
> 
> Of course at the loading, when the News seems not related to any Label
> because the "labels" field is empty.
> A workaround it to change the @JoinColumns from:
> 
> @JoinColumns({@JoinColumn(name="news_topic_fk", referencedColumnName =
> "newsid.title", nullable = false) ,
>          @JoinColumn(name="news_author_fk", referencedColumnName =
> "newsid.author", nullable = false)})
> private List<Label> labels;
> 
> @JoinColumns({@JoinColumn(name="title", referencedColumnName =
> "newsid.title", nullable = false) ,
>          @JoinColumn(name="author", referencedColumnName =
> "newsid.author", nullable = false)})
> private List<Label> labels;
> 
> Note that the new value of each @JoinColumn's name is the same as
> referenced property from the @Embedded entity.
> 
> I see there are 2 fix possible for this issue:
> - we can say in case of IN_ENTITY mode don't use @JoinColumns' name to
> store the navigation property but the property from the referenced
> column.
> - at the loading, we can check also the documents created due to @JoinColumns
> 
> Personally, I would tend to the first approach which is more natural
> in terms of storage and more readable.
> 
> What do you think ?
> Let me know if you need more information.
> 
> Guillaume
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