Deleting documents works similarly to finding documents. We need to find documents and then apply the delete operation.

For example, with our books collection used before, we can issue:

@collection.find( { isbn: '101' } ).delete_one

This will delete a single document. In our case, since isbn is unique for every document, this is expected. If our find() clause had matched multiple documents, then delete_one would have deleted just the first one that find() returns, which may or may not be what we want.

If we want to delete all documents matching our find() query, we have to use delete_many, like this:

@collection.find( { price: { $gte: 30 } ).delete_many

In the preceding example, we are deleting all books that have a price greater than or equal to 30.