Storing DBRef as Embedded Document for Easy Use In Aggregation Framework or Extension point for Serialization and Deserialization of DBRef [DATAMONGO-1878]

[spring-projects-issues]

Ankur Pathak opened DATAMONGO-1878 and commented

@Document(collection = "users")
class User {
  @Id
  String id;

  @DBRef
  Organization organization;

  String name;
}

@Document(collection = "organizations")
class Organization {
  @Id
  String id;
  
}

User will be stored in MongoDb like:

{
    "_id": "1",
    "organization": {
        "$ref": "organizations",
        "$id": 1
    },
    "name" : "Ankur Pathak"
}

But if we try to use DBRef in aggreagation framework of MongoDb like below we will get error:

db.users.aggregate({ $group: {
    _id: { name: "$name", orgId: "$organization.$id"}
}})

Their is a ugly way to use them in aggregation framework by converting them to array and then into object something like this:

db.foo.aggregate([{$project: {x: {$objectToArray: "$$ROOT.ref"}}}])

Check this url for reference and more detail: SERVER-14466

It will be great if we have some different or pluggable way for serialiazation and deserialization of
DBRef s. Something like this:

@Document(collection = "users")
class User {
  @Id
  String id;

  @DBRef(embedded=true) or @EmbeddedDBRef
  Organization organization;

  String name;
}

User will be stored in MongoDb like:

{
    "_id": "1",
    "organization": {
        "namespace": "organizations",
        "id": 1
    },
    "name" : "Ankur Pathak"
}

Now I can easily use use DBref in aggregation frmaework like this:

db.users.aggregate({ $group: {
    _id: { name: "$name", orgId: "$organization.id"}
}})

Storing dbref like this will make them easily useable in aggregation framework
and for left joins in aggreagation framework($lookup).

---

Reference URL: https://jira.mongodb.org/browse/SERVER-14466

[christophstrobl]

support added via #3602