@@ -14,22 +14,29 @@ Aggregation
1414
1515.. contents:: On this page
1616 :local:
17+
1718 :backlinks: none
1819 :depth: 2
1920 :class: singlecol
2021
22+ .. toctree::
23+
24+ Pipeline Stages </aggregation/pipeline-stages>
25+
2126.. _nodejs-aggregation-overview:
2227
2328Overview
2429--------
2530
26- In this guide, you can learn how to use **aggregation operations** in
27- the MongoDB Node.js driver .
31+ In this guide, you can learn how to use the MongoDB Node.js Driver to perform
32+ **aggregation operations** .
2833
29- Aggregation operations are expressions you can use to produce reduced
30- and summarized results in MongoDB. MongoDB's aggregation framework
31- allows you to create a pipeline that consists of one or more stages,
32- each of which performs a specific operation on your data.
34+ Aggregation operations process data in your MongoDB collections and return
35+ computed results. The MongoDB Aggregation framework is modeled on the
36+ concept of data processing pipelines. Documents enter a pipeline comprised of one or
37+ more stages, and this pipeline transforms the documents into an aggregated result.
38+
39+ To learn more about the aggregation stages supported by the Node.js Driver, see :ref:`Aggregation Stages <node-aggregation-pipeline-stages>`.
3340
3441.. _node-aggregation-tutorials:
3542
@@ -42,114 +49,67 @@ each of which performs a specific operation on your data.
4249Analogy
4350~~~~~~~
4451
45- You can think of the aggregation pipeline as similar to an automobile factory.
46- Automobile manufacturing requires the use of assembly stations organized
47- into assembly lines. Each station has specialized tools, such as
48- drills and welders. The factory transforms and
49- assembles the initial parts and materials into finished products.
50-
51- The **aggregation pipeline** is the assembly line, **aggregation
52- stages** are the assembly stations, and **expression operators** are the
53- specialized tools.
54-
55- Comparing Aggregation and Query Operations
56- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
57-
58- Using query operations, such as the ``find()`` method, you can perform the following actions:
59-
60- - Select *which documents* to return
61- - Select *which fields* to return
62- - Sort the results
63-
64- Using aggregation operations, you can perform the following actions:
65-
66- - Perform all query operations
67- - Rename fields
68- - Calculate fields
69- - Summarize data
70- - Group values
71-
72- Aggregation operations have some :manual:`limitations </core/aggregation-pipeline-limits/>`:
73-
74- - Returned documents must not violate the :manual:`BSON-document size limit </reference/limits/#mongodb-limit-BSON-Document-Size>`
52+ The aggregation pipeline is similar to an automobile factory assembly line. An
53+ assembly line has stations with specialized tools that are used to perform
54+ specific tasks. For example, when building a car, the assembly line begins with
55+ a frame. As the car frame moves though the assembly line, each station assembles
56+ a separate part. The result is a transformed final product, the finished car.
57+
58+ The *aggregation pipeline* is the assembly line, the *aggregation stages* are
59+ the assembly stations, the *expression operators* are the specialized tools, and
60+ the *aggregated result* is the finished product.
61+
62+ Compare Aggregation and Find Operations
63+ ---------------------------------------
64+
65+ The following table lists the different tasks you can perform with find
66+ operations compared to what you can achieve with aggregation
67+ operations. The aggregation framework provides expanded functionality
68+ that allows you to transform and manipulate your data.
69+
70+ .. list-table::
71+ :header-rows: 1
72+ :widths: 50 50
73+
74+ * - Find Operations
75+ - Aggregation Operations
76+
77+ * - | Select *certain* documents to return
78+ | Select *which* fields to return
79+ | Sort the results
80+ | Limit the results
81+ | Count the results
82+ - | Select *certain* documents to return
83+ | Select *which* fields to return
84+ | Sort the results
85+ | Limit the results
86+ | Count the results
87+ | Group the results
88+ | Rename fields
89+ | Compute new fields
90+ | Summarize data
91+ | Connect and merge data sets
92+
93+ Server Limitations
94+ ------------------
95+
96+ Consider the following :manual:`limitations </core/aggregation-pipeline-limits/>` when performing aggregation operations:
97+
98+ - Returned documents must not violate the :manual:`BSON document size limit </reference/limits/#mongodb-limit-BSON-Document-Size>`
7599 of 16 megabytes.
76100
77- - Pipeline stages have a memory limit of 100 megabytes by default. You can exceed this
78- limit by setting the ``allowDiskUse`` property of ``AggregateOptions`` to ``true``. See
79- the `AggregateOptions API documentation <{+api+}/interfaces/AggregateOptions.html>`__
80- for more details.
81-
82- .. important:: $graphLookup exception
83-
84- The :manual:`$graphLookup
85- </reference/operator/aggregation/graphLookup/>` stage has a strict
86- memory limit of 100 megabytes and will ignore ``allowDiskUse``.
87-
88- References
89- ~~~~~~~~~~
90-
91- To view a full list of expression operators, see :manual:`Aggregation
92- Operators </reference/operator/aggregation/>` in the Server manual.
93-
94- To learn about assembling an aggregation pipeline and view examples, see
95- :manual:`Aggregation Pipeline </core/aggregation-pipeline/>` in the
96- Server manual.
97-
98- To learn more about creating pipeline stages, see :manual:`Aggregation
99- Stages </reference/operator/aggregation-pipeline/>` in the Server manual.
100-
101- Runnable Examples
102- -----------------
103-
104- The example uses sample data about restaurants. The following code
105- inserts data into the ``restaurants`` collection of the ``aggregation``
106- database:
107-
108- .. literalinclude:: /code-snippets/aggregation/agg.js
109- :start-after: begin data insertion
110- :end-before: end data insertion
111- :language: javascript
112- :dedent:
113-
114- .. tip::
115-
116- For more information on connecting to your MongoDB deployment, see the :doc:`Connection Guide </connect>`.
117-
118- Aggregation Example
119- ~~~~~~~~~~~~~~~~~~~
120-
121- To perform an aggregation, pass a list of aggregation stages to the
122- ``collection.aggregate()`` method.
123-
124- In the example, the aggregation pipeline uses the following aggregation stages:
125-
126- - A :manual:`$match </reference/operator/aggregation/match/>` stage to filter for documents whose
127- ``categories`` array field contains the element ``Bakery``.
128-
129- - A :manual:`$group </reference/operator/aggregation/group/>` stage to group the matching documents by the ``stars``
130- field, accumulating a count of documents for each distinct value of ``stars``.
131-
132- .. literalinclude:: /code-snippets/aggregation/agg.js
133- :start-after: begin aggregation
134- :end-before: end aggregation
135- :language: javascript
136- :dedent:
137-
138- This example produces the following output:
139-
140- .. code-block:: json
141- :copyable: false
142-
143- { _id: 4, count: 2 }
144- { _id: 3, count: 1 }
145- { _id: 5, count: 1 }
101+ - Pipeline stages have a memory limit of 100 megabytes by default. If required,
102+ you can exceed this limit by enabling the `AllowDiskUse
103+ <https://mongodb.github.io/node-mongodb-native/6.17/interfaces/AggregateOptions.html#allowDiskUse>`__
104+ property of the ``AggregateOptions`` object that you pass to the
105+ ``Aggregate()`` method.
146106
147- For more information, see the `aggregate() API documentation <{+api+}/classes/Collection.html#aggregate>`__.
107+ Additional information
108+ ----------------------
148109
149- Additional Examples
150- ~~~~~~~~~~~~~~~~~~~
110+ To view a full list of expression operators, see
111+ :manual:`Aggregation Operators </reference/operator/aggregation/>`.
151112
152- You can find another aggregation pipeline example in the `Aggregation
153- Framework with Node.js Tutorial
154- <https://www.mongodb.com/blog/post/quick-start-nodejs--mongodb--how-to-analyze-data-using-the-aggregation-framework>`_
155- blog post on the MongoDB website.
113+ To learn about explaining MongoDB aggregation operations, see
114+ :manual:`Explain Results </reference/explain-results/>` and
115+ :manual:`Query Plans </core/query-plans/>`.
0 commit comments