Driver Examples (Node.js, Python, Java)

Parent: MongoDB Aggregation Pipeline · Published reference · snapshot 2026-10-15

Depth-first rabbithole dossier for Driver Examples (Node.js, Python, Java); source-anchored research pack.

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Facts and statements

[low] In Java, aggregations are created by invoking the `newAggregation(…)` static factory method of the `Aggregation` class, which accepts a list of `AggregateOperation` and an optional input class. Sources: https://docs.spring.io/spring-data/mongodb/reference/mongodb/aggregation-framework.html [source]
[low] In Java, the aggregate operation is executed by the `aggregate` method of `MongoTemplate`, which takes the desired output class as a parameter. Sources: https://docs.spring.io/spring-data/mongodb/reference/mongodb/aggregation-framework.html [source]
[low] In Java, unsupported aggregation stages like `$search` for MongoDB Atlas can be provided by implementing the `AggregationOperation` interface. Sources: https://docs.spring.io/spring-data/mongodb/reference/mongodb/aggregation-framework.html [source]
[low] In Java, `Aggregation.stage` is a shortcut for registering a pipeline stage by providing its JSON or Bson representation. Sources: https://docs.spring.io/spring-data/mongodb/reference/mongodb/aggregation-framework.html [source]
[low] In Java, `SetWindowFieldsOperation` implements `AggregationOperation` and `InheritsFieldsAggregationOperation` to support the `$setWindowFields` stage. Sources: https://docs.spring.io/spring-data/mongodb/docs/current/api/org/springframework/data/mongodb/core/aggregation/SetWindowFieldsOperation.html [source]
[low] In Java, `SetWindowFieldsOperation` includes a fluent builder, `SetWindowFieldsOperationBuilder`, for creating instances of the operation. Sources: https://docs.spring.io/spring-data/mongodb/docs/current/api/org/springframework/data/mongodb/core/aggregation/SetWindowFieldsOperation.html [source]
[low] In Java, `SetWindowFieldsOperation.WindowOutput` defines the output of the `$setWindowFields` stage by specifying fields to append to documents. Sources: https://docs.spring.io/spring-data/mongodb/docs/current/api/org/springframework/data/mongodb/core/aggregation/SetWindowFieldsOperation.html [source]
[low] In Java, `SetWindowFieldsOperation.RangeWindow` is a `Window` implementation based on sort fields. Sources: https://docs.spring.io/spring-data/mongodb/docs/current/api/org/springframework/data/mongodb/core/aggregation/SetWindowFieldsOperation.html [source]
[low] In Java, `SetWindowFieldsOperation.DocumentWindow` is a `Window` implementation based on the current document. Sources: https://docs.spring.io/spring-data/mongodb/docs/current/api/org/springframework/data/mongodb/core/aggregation/SetWindowFieldsOperation.html [source]
[low] To explain an aggregation operation, you can use the PyMongoExplain library or a database command. Sources: https://www.mongodb.com/docs/languages/python/pymongo-driver/current/aggregation.md [source]
[low] In Node.js, `Model.aggregate()` accepts an array of stage objects, such as `{ $project: { a: 1, b: 1 } }` and `{ $skip: 5 }`. Sources: https://mongoosejs.com/docs/api/aggregate.html [source]
[low] In Node.js, `Model.aggregate()` can be chained with methods like `.unwind('tags')` and executed with `.exec()`. Sources: https://mongoosejs.com/docs/api/aggregate.html [source]
[low] In Node.js, `Model.aggregate()` can be configured with `.allowDiskUse(true)` to allow disk usage during aggregation. Sources: https://mongoosejs.com/docs/api/aggregate.html [source]
[low] In Node.js, `Model.aggregate()` can return a cursor with a specified batch size using `.cursor({ batchSize: 1000 })`. Sources: https://mongoosejs.com/docs/api/aggregate.html [source]
[low] In Node.js, `Model.aggregate()` supports the `.facet()` method to apply multiple aggregation pipelines, such as grouping by author and bucketing prices. Sources: https://mongoosejs.com/docs/api/aggregate.html [source]
[low] In Node.js, `aggregate.densify()` can be used to fill gaps in a time series by specifying a field and range with step, unit, and bounds. Sources: https://mongoosejs.com/docs/api/aggregate.html [source]
[low] In Node.js, `aggregate.fill()` can be used to fill missing values in specific fields with default values, such as setting `bootsSold` to 0. Sources: https://mongoosejs.com/docs/api/aggregate.html [source]
[low] In Node.js, `Model.aggregate()` can specify a hint for index usage using `.hint({ qty: 1, category: 1 })` before executing with `.exec()`. Sources: https://mongoosejs.com/docs/api/aggregate.html [source]
[low] In Node.js, `Model.aggregate()` can set options like `allowDiskUse` using the `.option()` method. Sources: https://mongoosejs.com/docs/api/aggregate.html [source]
[low] In Node.js, `MyModel.aggregate().match({ test: 1 }).pipeline()` returns the pipeline array `[{ $match: { test: 1 } }]`. Sources: https://mongoosejs.com/docs/api/aggregate.html [source]
[low] In Node.js, `base.pipelineForUnionWith()` returns the pipeline array for use with `$unionWith`, such as `[{ $match: { test: 1 } }]`. Sources: https://mongoosejs.com/docs/api/aggregate.html [source]
[low] In Node.js, `aggregate.project()` can accept a string like "a b -_id" to specify fields to include or exclude. Sources: https://mongoosejs.com/docs/api/aggregate.html [source]
[low] In Node.js, `Model.aggregate()` can set the read preference using `.read('primaryPreferred')`. Sources: https://mongoosejs.com/docs/api/aggregate.html [source]
[low] In Node.js, `Model.aggregate()` can set the read concern using `.readConcern('majority')`. Sources: https://mongoosejs.com/docs/api/aggregate.html [source]
[low] In Node.js, `Model.aggregate()` can apply a redaction expression using `.redact()` with conditions like `$eq` and actions like `$$PRUNE` or `$$DESCEND`. Sources: https://mongoosejs.com/docs/api/aggregate.html [source]
[low] In Node.js, `aggregate.replaceRoot()` can be used to replace the root document with a specified field, such as "user". Sources: https://mongoosejs.com/docs/api/aggregate.html [source]
[low] In Node.js, `aggregate.sample(3)` adds a pipeline stage that picks 3 random documents. Sources: https://mongoosejs.com/docs/api/aggregate.html [source]
[low] In Node.js, `Model.aggregate()` can perform a text search using `.search({ text: { query: 'baseball', path: 'plot' } })`. Sources: https://mongoosejs.com/docs/api/aggregate.html [source]
[low] In Node.js, `Model.aggregate()` can be associated with a session using `.session(session)` after starting a session with `Model.startSession()`. Sources: https://mongoosejs.com/docs/api/aggregate.html [source]
[low] In Node.js, `aggregate.sort()` can sort documents by multiple fields with ascending or descending order, such as `{ field: 'asc', test: -1 }`. Sources: https://mongoosejs.com/docs/api/aggregate.html [source]
[low] In Node.js, `aggregate.sortByCount('users')` sorts documents by the count of a specified field. Sources: https://mongoosejs.com/docs/api/aggregate.html [source]
[low] In Node.js, `aggregate.unionWith()` can combine results from another collection with an optional pipeline, such as `{ coll: 'users', pipeline: [ { $match: { _id: 1 } } ] }`. Sources: https://mongoosejs.com/docs/api/aggregate.html [source]
[low] In Node.js, `aggregate.unwind("tags")` deconstructs an array field into multiple documents. Sources: https://mongoosejs.com/docs/api/aggregate.html [source]
[low] In Java, referencing non-existent properties in aggregations no longer raises errors in version 3.2; the previous behavior can be restored using the `strictMapping` option of `AggregationOptions`. (verified as of 2026-10-15) Sources: https://docs.spring.io/spring-data/mongodb/reference/mongodb/aggregation-framework.html [source]

Related concepts

Node.js — is a part of Driver Examples (Node.js, Python, Java)
Java — is a part of Driver Examples (Node.js, Python, Java)
Python — is a part of Driver Examples (Node.js, Python, Java)

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