Aggregation stages

Aggregation stages are a series of one or more processes in a pipeline that acts upon the returned result of the previous stage, starting with the input documents.

Supported aggregation stages	Description
$count	Returns the count of all matched documents in a specified query
$group	Groups documents based on specific value or expression and returns a single document for each group
$limit	Limits specific documents and passes the rest to the next stage
$match	Acts as a find operation by only returning documents that match a specified query to the next stage
$project	Specifies the fields in a document to pass to the next stage in the pipeline
$skip	Skips a specified n number of documents and passes the rest to the next stage
$sort	Sorts and returns all the documents based on a specified order
$unset	Specifies the fields to be removed/excluded from a document
$unwind	Deconstructs and returns a document for every element in an array field