Outputs documents in order of nearest to farthest from a specified point. MongoDB Documentation: https://docs.mongodb.com/manual/reference/operator/aggregation/geoNear/#pipe._S_geoNear
Groups documents by some specified expression and outputs to the next stage a document for each distinct grouping. The output documents contain an _id field which contains the distinct group by key. The output documents can also contain computed fields that hold the values of some accumulator expression grouped by the $group‘s _id field. $group does not order its output documents. MongoDB Documentation: https://docs.mongodb.com/manual/reference/operator/aggregation/group/#pipe._S_group
Groups all documents into one specified with the accumulators. Basically just runs group(null, accumulators)
Returns statistics regarding the use of each index for the collection. If running with access control, the user must have privileges that include indexStats action. MongoDB Documentation: https://docs.mongodb.com/manual/reference/operator/aggregation/indexStats/#pipe._S_indexStats
Limits the number of documents passed to the next stage in the pipeline. MongoDB Documentation: https://docs.mongodb.com/manual/reference/operator/aggregation/limit/#pipe._S_limit
Performs a left outer join to an unsharded collection in the same database to filter in documents from the “joined” collection for processing. The $lookup stage does an equality match between a field from the input documents with a field from the documents of the “joined” collection. To each input document, the $lookup stage adds a new array field whose elements are the matching documents from the “joined” collection. The $lookup stage passes these reshaped documents to the next stage. MongoDB Documentation: https://docs.mongodb.com/manual/reference/operator/aggregation/lookup/#pipe._S_lookup
Filters the documents to pass only the documents that match the specified condition(s) to the next pipeline stage. MongoDB Documentation: https://docs.mongodb.com/manual/reference/operator/aggregation/match/#pipe._S_match
Takes the documents returned by the aggregation pipeline and writes them to a specified collection. The $out operator must be the last stage in the pipeline. The $out operator lets the aggregation framework return result sets of any size. MongoDB Documentation: https://docs.mongodb.com/manual/reference/operator/aggregation/out/#pipe._S_out
Passes along the documents with only the specified fields to the next stage in the pipeline. The specified fields can be existing fields from the input documents or newly computed fields. MongoDB Documentation: https://docs.mongodb.com/manual/reference/operator/aggregation/project/#pipe._S_project
Restricts the contents of the documents based on information stored in the documents themselves. MongoDB Documentation: https://docs.mongodb.com/manual/reference/operator/aggregation/redact/#pipe._S_redact
Randomly selects the specified number of documents from its input. Warning: $sample may output the same document more than once in its result set. MongoDB Documentation: https://docs.mongodb.com/manual/reference/operator/aggregation/sample/#pipe._S_sample
Skips over the specified number of documents that pass into the stage and passes the remaining documents to the next stage in the pipeline. MongoDB Documentation: https://docs.mongodb.com/manual/reference/operator/aggregation/skip/#pipe._S_skip
Sorts all input documents and returns them to the pipeline in sorted order. MongoDB Documentation: https://docs.mongodb.com/manual/reference/operator/aggregation/sort/#pipe._S_sort
Deconstructs an array field from the input documents to output a document for each element. Each output document is the input document with the value of the array field replaced by the element. MongoDB Documentation: https://docs.mongodb.com/manual/reference/operator/aggregation/unwind/#pipe._S_unwind
Deconstructs an array field from the input documents to output a document for each element. Each output document is the input document with the value of the array field replaced by the element. MongoDB Documentation: https://docs.mongodb.com/manual/reference/operator/aggregation/unwind/#pipe._S_unwind
Deconstructs an array field from the input documents to output a document for each element. Each output document is the input document with the value of the array field replaced by the element. MongoDB Documentation: https://docs.mongodb.com/manual/reference/operator/aggregation/unwind/#pipe._S_unwind