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.. _node-aggregation:
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.. _nodejs-aggregation:
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- ===========
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- Aggregation
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- ===========
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+ ======================
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+ Aggregation Operations
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+ ======================
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.. facet::
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:name: genre
@@ -18,18 +18,27 @@ Aggregation
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:depth: 2
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:class: singlecol
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+ .. toctree::
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+ :titlesonly:
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+ :maxdepth: 1
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+
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+ Pipeline Stages </aggregation/pipeline-stages>
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+
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.. _nodejs-aggregation-overview:
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Overview
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--------
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- In this guide, you can learn how to use **aggregation operations** in
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- the MongoDB Node.js driver.
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+ In this guide, you can learn how to use the {+driver-long+} to perform
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+ **aggregation operations**.
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+
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+ Aggregation operations process data in your MongoDB collections and return
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+ computed results. The MongoDB Aggregation framework is modeled on the concept of
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+ data processing pipelines. Documents enter a pipeline comprised of one or more
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+ stages, and this pipeline transforms the documents into an aggregated result.
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- Aggregation operations are expressions you can use to produce reduced
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- and summarized results in MongoDB. MongoDB's aggregation framework
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- allows you to create a pipeline that consists of one or more stages,
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- each of which performs a specific operation on your data.
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+ To learn more about the aggregation stages supported by the {+driver-short+},
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+ see :ref:`node-aggregation-pipeline-stages`.
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.. _node-aggregation-tutorials:
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@@ -42,114 +51,67 @@ each of which performs a specific operation on your data.
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Analogy
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~~~~~~~
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- You can think of the aggregation pipeline as similar to an automobile factory.
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- Automobile manufacturing requires the use of assembly stations organized
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- into assembly lines. Each station has specialized tools, such as
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- drills and welders. The factory transforms and
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- assembles the initial parts and materials into finished products.
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-
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- The **aggregation pipeline** is the assembly line, **aggregation
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- stages** are the assembly stations, and **expression operators** are the
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- specialized tools.
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-
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- Comparing Aggregation and Query Operations
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- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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-
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- Using query operations, such as the ``find()`` method, you can perform the following actions:
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-
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- - Select *which documents* to return
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- - Select *which fields* to return
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- - Sort the results
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-
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- Using aggregation operations, you can perform the following actions:
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-
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- - Perform all query operations
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- - Rename fields
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- - Calculate fields
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- - Summarize data
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- - Group values
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-
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- Aggregation operations have some :manual:`limitations </core/aggregation-pipeline-limits/>`:
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-
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- - Returned documents must not violate the :manual:`BSON-document size limit </reference/limits/#mongodb-limit-BSON-Document-Size>`
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- of 16 megabytes.
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-
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- - Pipeline stages have a memory limit of 100 megabytes by default. You can exceed this
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- limit by setting the ``allowDiskUse`` property of ``AggregateOptions`` to ``true``. See
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- the `AggregateOptions API documentation <{+api+}/interfaces/AggregateOptions.html>`__
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- for more details.
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-
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- .. important:: $graphLookup exception
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-
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- The :manual:`$graphLookup
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- </reference/operator/aggregation/graphLookup/>` stage has a strict
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- memory limit of 100 megabytes and will ignore ``allowDiskUse``.
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-
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- References
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- ~~~~~~~~~~
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-
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- To view a full list of expression operators, see :manual:`Aggregation
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- Operators </reference/operator/aggregation/>` in the Server manual.
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-
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- To learn about assembling an aggregation pipeline and view examples, see
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- :manual:`Aggregation Pipeline </core/aggregation-pipeline/>` in the
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- Server manual.
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-
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- To learn more about creating pipeline stages, see :manual:`Aggregation
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- Stages </reference/operator/aggregation-pipeline/>` in the Server manual.
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-
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- Runnable Examples
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- -----------------
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-
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- The example uses sample data about restaurants. The following code
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- inserts data into the ``restaurants`` collection of the ``aggregation``
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- database:
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-
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- .. literalinclude:: /code-snippets/aggregation/agg.js
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- :start-after: begin data insertion
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- :end-before: end data insertion
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- :language: javascript
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- :dedent:
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-
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- .. tip::
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-
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- For more information on connecting to your MongoDB deployment, see the :doc:`Connection Guide </connect>`.
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-
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- Aggregation Example
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- ~~~~~~~~~~~~~~~~~~~
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-
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- To perform an aggregation, pass a list of aggregation stages to the
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- ``collection.aggregate()`` method.
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-
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- In the example, the aggregation pipeline uses the following aggregation stages:
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-
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- - A :manual:`$match </reference/operator/aggregation/match/>` stage to filter for documents whose
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- ``categories`` array field contains the element ``Bakery``.
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-
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- - A :manual:`$group </reference/operator/aggregation/group/>` stage to group the matching documents by the ``stars``
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- field, accumulating a count of documents for each distinct value of ``stars``.
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-
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- .. literalinclude:: /code-snippets/aggregation/agg.js
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- :start-after: begin aggregation
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- :end-before: end aggregation
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- :language: javascript
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- :dedent:
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-
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- This example produces the following output:
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-
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- .. code-block:: json
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- :copyable: false
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-
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- { _id: 4, count: 2 }
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- { _id: 3, count: 1 }
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- { _id: 5, count: 1 }
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-
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- For more information, see the `aggregate() API documentation <{+api+}/classes/Collection.html#aggregate>`__.
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-
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- Additional Examples
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- ~~~~~~~~~~~~~~~~~~~
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-
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- You can find another aggregation pipeline example in the `Aggregation
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- Framework with Node.js Tutorial
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- <https://www.mongodb.com/blog/post/quick-start-nodejs--mongodb--how-to-analyze-data-using-the-aggregation-framework>`_
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- blog post on the MongoDB website.
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+ The aggregation pipeline is similar to an automobile factory assembly line. An
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+ assembly line has stations with specialized tools that are used to perform
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+ specific tasks. For example, when building a car, the assembly line begins with
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+ a frame. As the car frame moves though the assembly line, each station assembles
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+ a separate part. The result is a transformed final product, the finished car.
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+
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+ The *aggregation pipeline* is the assembly line, the *aggregation stages* are
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+ the assembly stations, the *expression operators* are the specialized tools, and
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+ the *aggregated result* is the finished product.
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+
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+ Compare Aggregation and Find Operations
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+ ---------------------------------------
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+
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+ The following table lists the different tasks you can perform with find
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+ operations compared to what you can achieve with aggregation operations. The
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+ aggregation framework provides expanded functionality that allows you to
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+ transform and manipulate your data.
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+
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+ .. list-table::
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+ :header-rows: 1
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+ :widths: 50 50
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+
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+ * - Find Operations
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+ - Aggregation Operations
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+
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+ * - | Select *certain* documents to return
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+ | Select *which* fields to return
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+ | Sort the results
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+ | Limit the results
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+ | Count the results
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+ - | Select *certain* documents to return
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+ | Select *which* fields to return
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+ | Sort the results
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+ | Limit the results
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+ | Count the results
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+ | Group the results
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+ | Rename fields
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+ | Compute new fields
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+ | Summarize data
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+ | Connect and merge data sets
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+
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+ Server Limitations
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+ ------------------
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+
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+ Consider the following :manual:`limitations
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+ </core/aggregation-pipeline-limits/>` when performing aggregation operations:
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+
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+ - Returned documents must not violate the :manual:`BSON document size limit
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+ </reference/limits/#mongodb-limit-BSON-Document-Size>` of 16 megabytes.
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+ - Pipeline stages have a memory limit of 100 megabytes by default. If required,
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+ you can exceed this limit by enabling the `AllowDiskUse
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+ <https://mongodb.github.io/node-mongodb-native/6.17/interfaces/AggregateOptions.html#allowDiskUse>`__
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+ property of the ``AggregateOptions`` object that you pass to the
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+ ``aggregate()`` method.
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+
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+ Additional information
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+ ----------------------
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+ To view a full list of expression operators, see :manual:`Aggregation Operators
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+ </reference/operator/aggregation/>` in the {+mdb-server+} manual.
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+
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+ To learn about explaining MongoDB aggregation operations, see :manual:`Explain
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+ Results </reference/explain-results/>` and :manual:`Query Plans
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+ </core/query-plans/>` in the {+mdb-server+} manual.
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