MongoDB - is DBREF necessary?

mongodb dbref
Industrial picture Industrial · Feb 23, 2012 · Viewed 27.2k times · Source

Using the DBREF datatype in MongoDB, a document may look like as shown below. But having the $ref field in every row feels redundant as every row obviously points to the users collection.

Is there a way to reference other documents without having the somewhat redundant $ref-field?

{
    $id: {$oid : "4f4603820e25f4c515000001"},
    title:   "User group",
    users: [ 
        {_id: {$ref: "users", $id: { $oid: "4f44af6a024342300e000002"}}, isAdmin: true }
    ]
],

Answer

Andrew Orsich picture Andrew Orsich · Feb 23, 2012

Dbref in my opinion should be avoided when work with mongodb, at least if you work with big systems that require scalability.

As i know all drivers make additional request to load DBRef, so it's not 'join' within database, it is very expensive.

Is there a way to reference other documents without having the somewhat redundant $ref-field?

Yes, keep references in the mind, create naming conventions for 'foreign keys' (something like RefUserId or just UserId) and store just id of referenced document. Load referenced documents yourself when needed. Also keep your eyes open for any denormalization, embedding you can do, because it's usually greatly improve performance.

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