Does querying Mongoid embedded documents hit the database server after loading a parent document

Question

Mongoid allows one to query both references and embedded documents using methods like find_by or where .

Say I have a model, Project , which embeds many Tasks . When I want to find a specific task, I am currently performing the following operation:

project = Project.find(...)
task = project.tasks.find_by(:some_field => 'Some Value')

My question is this, does the find_by query on the embedded tasks above issue another query to the Mongo database, or does it recognize that tasks are embedded in the given project and instead filter the tasks locally?

Thank you

Answer 1

Nope, it does not do another query.

Embedded documents are basically denormalized. http://docs.mongodb.org/manual/core/data-model-design/#data-modeling-embedding

If you are interested in seeing the queries yourself, you can turn it on: How can I see raw mongoDB queries with Mongoid