FAQ

This FAQ answers basic questions for new evaluators of MongoDB. See also:

• Developer FAQ
• Sharding FAQ

MongoDB Intro FAQ

What kind of database is the Mongo database?

MongoDB is an document-oriented DBMS. Think of it as MySQL but JSON (actually, BSON ) as the data model, not relational. There are no joins.  If you have used object-relational mapping layers before in your programs, you will find the Mongo interface similar to use, but faster, more powerful, and less work to set up.

What languages can I use to work with the Mongo database?

Lots!  See the drivers page.

Does it support SQL?

No, but MongoDB does support ad hoc queries via a JSON-style query language.  See the Tour and Advanced Queries pages for more information on how one performs operations.

Is caching handled by the database?

For simple queries (with an index) Mongo should be fast enough that you can query the database directly without needing the equivalent of memcached. The goal is for Mongo to be an alternative to an ORM/memcached/mysql stack.  Some MongoDB users do like to mix it with memcached though.

What language is MongoDB written in?

The database is written in C++.  Drivers are usually written in their respective languages, although some use C extensions for speed.

What are the 32-bit limitations?

MongoDB uses memory-mapped files.  When running on a 32-bit operating system, the total storage size for the server (data, indexes, everything) is 2gb. If you are running on a 64-bit os, there is virtually no limit to storage size.  See the blog post for more information.