Support Spring Data @Reference annotation [DATAMONGO-915]

[spring-projects-issues]

David Rauschenbach opened DATAMONGO-915 and commented

There's currently no support for manually loaded lazy references.

@DBRef is a bit of a mess right now for a few reasons:

1. Big systems don't use it, because it wastes storage space for no good reason. The exception being when db is not blank, for a cross-database reference.

2. It triggers some drivers to eager-load, but that's not always what is always wanted. A developer might really rather manually deference a field to trigger the lazy load, especially if it is a big database or a realtime capped collection tailing use case. In my opinion the Mongo Spring Data driver really MUST provide a single-query option for loading a doc with reference fields.

3. It requires Mongo-specific annotations, and doesn't inherit some of the reasonable Spring Data or JPA annotations that people will be using who are writing systems that have heterogeneous DB support, like @Reference or @Embedded hints.

The Spring Data @Reference annotation is an opportunity to deal with some of these things. It could become the means by which a simple ObjectId() is written into the DB

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Affects: 1.4.2 (Codd SR2)

3 votes, 3 watchers

[spring-projects-issues]

Tudor Matei commented

I would really like this feature as well. I have a pre-existing mongodb database that contains manual references.
http://docs.mongodb.org/manual/reference/database-references/#document-references

Any idea when this can be added?

[spring-projects-issues]

Raviteja commented

I agree that DBRef is a mess, can't use it in aggregation pipeline because of mongodb doesn't support it. I have to rely on map-reduce instead of using simple aggregation pipeline to fetch the data.

FYI,

• Mongo Morphia allows: @Reference(idOnly=true)
  • http://mongodb.github.io/morphia/1.3/javadoc/org/mongodb/morphia/annotations/Reference.html
• GORM: Usage of manual references is default
  • http://gorm.grails.org/latest/mongodb/manual/index.html#releaseNotes Read 1.1 GA release notes
  • http://gorm.grails.org/latest/mongodb/manual/index.html#_customized_collection_and_database_mapping

[christophstrobl]

Resolved via: #3647