Database Reference
In-Depth Information
Chapter 5
GridFS
We live in a world of high-definition video, 12MP cameras, and storage media that can
hold 50GB of data on a disc the size of a CD-ROM. In that context, the 16MB limit for the
maximum size of a MongoDB document might seem laughably inadequate. Indeed, you
might wonder why MongoDB, which has been designed as a database for today's high-tech
age, has such a seemingly strange limitation. The short answer is performance.
If data were stored in the document itself, it would obviously get very large, which
in turn would make the data harder to work with. For example, pulling back the whole
document would require loading the files in the document, as well. You could work
around this issue, but you would still need to pull back the entire file whenever you
accessed it, even if you only wanted a small section of it. You can't ask for a chunk of data
in the middle of a document—it's an all-or-nothing proposition. Fortunately, MongoDB
features a unique and somewhat elegant solution to this problem. MongoDB enables
you to store large files quite easily, yet it also allows you to access parts of the file without
retrieving the entire thing—all while maintaining high performance. It achieves this by
leveraging a specification known as GridFS.
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One interesting thing about GridFS is that it isn't actually a software feature. For
example, there isn't any special server-side code in MongoDB that manages GridFS. Instead,
GridFS is a simple specification used by all of the supported drivers on MongoDB. The key
benefit of such a specification is that files stored by one driver can be accessed by any other
driver that follows the same convention.
Note
This approach adheres closely to the MongoDB principle of keeping things simple.
Because GridFS uses standard MongoDB features, it's easy to implement and work with
the specification from the driver's point of view. It also means you can poke around by
hand if you really want to, as to MongoDB files in the GridFS specification are just normal
collections containing documents.
