How can I discover a mongo database's structure

Question

I have a Mongo database that I did not create or architect, is there a good way to introspect the db or print out what the structure is to start to get a handle on what types of data are being stored, how the data types are nested, etc?

Answer 1

Just query the database by running the following commands in the mongo shell:

use mydb //this switches to the database you want to query show collections //this command will list all collections in the database db.collectionName.find().pretty() //this will show all documents in the database in a readable format; do the same for each collection in the database 

You should then be able to examine the document structure.

Answer 2

There is actually a tool to help you out here called Variety:

http://blog.mongodb.org/post/21923016898/meet-variety-a-schema-analyzer-for-mongodb

You can view the Github repo for it here: https://github.com/variety/variety

I should probably warn you that:

• It uses MR to accomplish its tasks
• It uses certain other queries that could bring a production set-up to a near halt in terms of performance.

As such I recommend you run this on a development server or a hidden node of a replica or something.

Depending on the size and depth of your documents it may take a very long time to understand the rough structure of your database through this but it will eventually give one.