- Manually/visually inspect the contents of the collection
- Use a utility to examine a single document
- Use some sort of utility to examine all of the documents in a collection
Manually inspecting the collection
As you can imagine is simply, "using" the database, and doing a db.collectionName.findOne()
For thoroughness, you'd probably want to examine more than one document. This is where a db.collectionName.find().pretty() will come in handy.
Use a utility to examine a single document
I created a small python utility given a database name and collection name will give you the keys for a document in the collection. This requires you have Python 2.7 and pymongo installed on your computer. I put this in my ~/bin directory and chmod +x it.
Use a utility to examine all of the documents in a collection
Skratch. has a cool extension to the MongoShell which examines all of the documents in a collection and tells you how many documents are using the field. Fields can vary in type by document. So, this tool even breaks down the occurrence of the field by type! It is on github at: https://github.com/skratchdot/mongodb-schema/