What is DBRef in MongoDB?

What is DBRef in MongoDB?

DBRefs are references from one document to another using the value of the first document’s _id field, collection name, and, optionally, its database name. By including these names, DBRefs allow documents located in multiple collections to be more easily linked with documents from a single collection.

Should I use DBRef?

DBref isn’t anything like a Foreign key in traditional relational systems. Its only a convention which easily tells a driver (who’s capable of) to autoload those referred documents. Basically, I would say that you should only use those DBrefs if the linked document can be of variable type.

What is the use of @DBRef?

Basically a DBRef is a self describing ObjectID which a client side helper, which exists in all drivers (I think all), provides the ability within your application to get related rows easily.

Which fields are in DBRefs?

DBRefs are made up of three fields:

• $ref: This field specifies the collection of the referenced document.
• $id: This field specifies the _id field of the referenced document.
• $db: This is an optional field and contains the name of the database in which the referenced document lies.

Do you need to create a reference in MongoDB?

The references are simple to create and your application can resolve references as needed. The only limitation of manual linking is that these references do not convey the database and collection names. If you have documents in a single collection that relate to documents in more than one collection, you may need to consider using DBRefs.

What are the limitations of manual linking in MongoDB?

The only limitation of manual linking is that these references do not convey the database and collection names. If you have documents in a single collection that relate to documents in more than one collection, you may need to consider using DBRefs. DBRefs are a convention for representing a document, rather than a specific reference type.

Where does the dbref point to in MongoDB?

The DBRef in this example points to a document in the creators collection of the users database that has ObjectId (“5126bc054aed4daf9e2ab772”) in its _id field. The order of fields in the DBRef matters, and you must use the above sequence when using a DBRef.

When to use dbrefs instead of manual references?

DBRefs provide a common format and type to represent relationships among documents. The DBRef format also provides common semantics for representing links between documents if your database must interact with multiple frameworks and tools. Unless you have a compelling reason to use DBRefs, use manual references instead.