Mongoid provides a DSL to build aggregation pipelines, but this is limited to the $group, $unwind, and $project stages. Additionally, a $match stage can be added using the query method, as per the documentation.

This feature would be significantly more helpful if it provided access to other aggregation pipeline stages as well. As is, any aggregation pipeline that uses other pipeline stages cannot use these helpers but rather needs to be assembled without using the builder DSL.