So this is a followup of my previous email (looks like I found out the
Send shortcut on GMail...)... which was supposed to be a followup of:
* https://hibernate.atlassian.net/browse/OGM-893
* https://github.com/hibernate/hibernate-ogm/pull/728
* and a discussion we had yesterday with Davide.
Taking MongoDB as the reference implementation here.
Current situation
=================
1/ for a simple embedded Address (property: homeAddress) with one of
the property having a @Column(name = "postal_code"), we end up with
the following mapping:
{
[...],
'homeAddress' : {
'city' : 'Paris',
'country' : 'France',
'street1' : '1 avenue des Champs Elysees',
'type' : {
'name' : 'main'
}
},
'postal_code' : '75007',
[...]
}
As you can see, postal_code is stored outside of the nested structure.
This is in line with the ORM behavior where you end up having the
columns homeAddress_city and postal_code.
Of course, this is a bit weird when we are considering nested documents.
See EmbeddableMappingTest for reference.
2/ now suppose that we have a List<Address>, the current mapping is
the following:
{
[...],
"addresses": [
{
"addresses": {
"country": "Germany",
"city": "Paris",
"street1": "1 avenue des Champs Elysees"
},
"postal_code": "75007"
},
{
"addresses": {
"city": "Rome",
"street1": "Piazza del Colosseo, 1",
"type": {
"name": "primary"
}
},
"postal_code": "00184"
}
],
[...]
}
Note the fact that addresses is nested twice.
This is discussed at length in https://hibernate.atlassian.net/browse/OGM-893.
What does PR 728 change?
========================
After the work we did with Steve on ORM and the followup of Davide on
OGM, we end up with the following situation:
1/ Same as before. postal_code is outside of the nested document.
2/ This is where the behavior has changed, we now have the following mapping:
{
"addresses": [
{
"country": "Germany",
"city": "Paris",
"street1": "1 avenue des Champs Elysees",
"postal_code": "75007"
},
{
"city": "Rome",
"street1": "Piazza del Colosseo, 1",
"type": {
"name": "primary"
},
"postal_code": "00184"
}
],
}
Note that postal_code and city are now at the same level.
See this future test executed on top of pr/728:
https://gist.github.com/gsmet/0652294523b2c48efe72668ccc0a6e1c
Conclusion
==========
So as you can see, the mapping is quite different between a simple
embedded and a list of embedded. I was not very happy with the
behavior of 2/ before, especially because if you remove the @Column,
you lose the data stored. Same if you didn't have one before and you
add one to your embeddable.
But I'm also not convinced having a different behavior between 1/ and
2/ is the way to go. Note that, from what I've seen, I don't think
changing 1/ to move postal_code in the nested document will be easy
(or even feasible).
Opinions? Thoughts?
--
Guillaume
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