Marko Anastasov wrote this on February 17, 2012

Beware of MongoDB's document size limit

Given I am MongoDB beginner
When designing a database for large quantities of data
Then I should be aware of the document size limit in BSON format

Including all embedded documents, MongoDB’s document size limit is currently 16 MB per document, unless you’re using GridFS (but it seems like if you can’t get GridFS from 3rd parties like MongoHQ or MongoLab?). Remember that MongoDB by default puts the working set of your database in RAM.

So if you expect to have millions of some things then you better put those things in a separate collection, even if semantically it may make more sense to embed them in another document. If you’re using mongoid that simply means having a stand-alone model referencing another model.

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About Marko Anastasov

Rendered Text co-founder. Started with code, currently more focused on people and words. Foosball striker and entry-level cyclist.

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