Transformation Pipeline Stages

3 Minutes to read

Share
Dark
Light

Article Summary

Share feedback

Thanks for sharing your feedback!

On this page, you will find a comprehensive list of transformation pipeline stages and their options.

Transformation Pipeline Stages

Stage Name	Description
`$addFields`	Adds new fields to documents.
`$bucket`	Groups documents into specified buckets based on an expression and boundaries. Options available.
`$bucketAuto`	Automatically distributes documents into a specified number of even buckets. Options available.
`$changeStream`	Returns a Change Stream cursor; must be the first stage in the pipeline.
`$collStats`	Provides statistics about a collection or view.
`$count`	Counts the documents at this pipeline stage.
`$currentOp`	Displays active and/or dormant operations. Requires the db.aggregate() method. Options available.
`$facet`	Executes multiple aggregation pipelines in one stage, enabling multi-faceted aggregations.
`$geoNear`	Orders documents based on geospatial proximity, incorporating $match, $sort, and $limit. Options available.
`$graphLookup`	Conducts a recursive search, appending results to the output document as an array. Options available.
`$group`	Groups documents by an expression, applying accumulator expressions to each group.
`$indexStats`	Reports usage statistics for each index in the collection.
`$limit`	Passes the first n documents unmodified to the pipeline.
`$listLocalSessions`	Lists active sessions on the connected mongos or mongod instance.
`$listSessions`	Lists sessions propagated to the system.sessions collection.
`$lookup`	Performs a left outer join with another collection in the same database. Options available.
`$match`	Filters documents, passing only matches to the next stage.
`$merge`	Writes aggregation results to a collection; must be the last stage in the pipeline. Options available.
`$out`	Writes aggregation results to a collection; must be the last stage. Options available.
`$planCacheStats`	Provides plan cache data for a collection.
`$project`	Reshapes each document, adding or removing fields.
`$redact`	Reshapes documents based on their content, allowing field level redaction.
`$replaceRoot`	Replaces a document with a specified embedded one, promoting the embedded document.
`$replaceWith`	Alias for `$replaceRoot`. Replaces a document with a specified embedded one.
`$sample`	Randomly selects a specified number of documents. Options available.
`$search`	Executes a full-text search.
`$set`	Alias for `$addFields`. Adds new fields to documents.
`$skip`	Skips the first n documents, passing the rest unmodified.
`$sort`	Reorders documents based on a specified sort key.
`$sortByCount`	Groups documents by an expression's value and counts them.
`$unionWith`	Combines results from two collections into one. Options available.
`$unset`	Removes specified fields from documents.
`$unwind`	Deconstructs an array field, outputting a document for each element. Options available.

Stages Options

Stage	Option
`$bucket`	`groupBy`: An expression to group by.
	`boundaries`: An array specifying the boundaries to group documents.
	`default`: A literal that specifies the `_id` of an additional group for all documents that do not match any boundary.
`$bucketAuto`	`groupBy`: An expression to group by.
	`buckets`: The number of buckets to create.
`$currentOp`	`allUsers`: A boolean indicating if operations from all users should be returned.
	`localOps`: A boolean indicating if only operations on the local mongod instance should be returned.
`$geoNear`	`near`: The geospatial point to calculate distances from.
	`distanceField`: The field that will contain the calculated distance.
	`spherical`: A boolean specifying whether to treat the `near` point as a sphere.
	`maxDistance`: The maximum distance from the `near` point that the documents can be.
`$graphLookup`	`from`: The target collection for the recursive search.
	`startWith`: The expression that specifies the value of the `connectFromField` with which to start the recursive search.
	`connectFromField`: The field whose value `startWith` references.
	`connectToField`: The field in the documents of the `from` collection that is equal to the `connectFromField`.
	`as`: The array field added to each output document that contains the search results.
`$lookup`	`from`: The target collection.
	`localField`: The field from the input documents.
	`foreignField`: The field from the documents of the `from` collection.
	`as`: The name of the new array field to add to the input documents.
`$merge`	`into`: The target collection.
	`on`: The fields to match on.
	`whenMatched`: The action to take when a matching document exists.
	`whenNotMatched`: The action to take when no matching document exists.
`$out`	`collection`: The target collection.
`$sample`	`size`: The number of documents to randomly select.
`$unionWith`	`coll`: The name of the collection to union with.
	`pipeline`: An optional aggregation pipeline to apply to the specified collection before performing the union.
`$unwind`	`path`: The path to the array field to unwind.
	`includeArrayIndex`: The name of a new field to hold the array index of the element.
	`preserveNullAndEmptyArrays`: A boolean indicating whether to include as an output document those documents that have an empty array or missing array field.

Was this article helpful?

What's Next

Transformation Pipeline Expressions

Table of contents