Documents

MongoDB can be thought of as a document-oriented database. By 'document', we mean structured documents, not freeform text documents. These documents can be thought of as objects but only the data of an object, not the code, methods or class hierarchy. Additionally, there is much less linking between documents in MongoDB data models than there is between objects in a program written in an object-oriented programming language.

In MongoDB the documents are conceptually JSON. More specifically the documents are represented in a format called BSON (standing for Binary JSON).

Documents are stored in Collections.

Maximum Document Size

MongoDB limits the data size of individual BSON objects/documents. At the time of this writing the limit is 16MB.

This limit is designed as a sanity-check; it is not a technical limit on document sizes. The thinking is that if documents are larger than this size, it is likely the schema is not ideal. Further it allows drivers to make some assumptions on the max size of documents.

The concept is that the maximum document size is a limit that ensures each document does not require an excessive amount of RAM from the machine, or require too much network bandwidth to fetch. For example, fetching a full 100MB document would take over 1 second to fetch over a gigabit ethernet connection. In this situation one would be limited to 1 request per second.

Over time, as computers grow in capacity, the limit will be adjusted upward.

For cases where larger sizes are required, use GridFS.