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8 changes: 5 additions & 3 deletions snooty.toml
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Expand Up @@ -13,7 +13,9 @@ toc_landing_pages = [
"/connect",
"/indexes",
"work-with-indexes",
"/data-formats"
"/data-formats",
"/builders",
"/aggregation"
]

sharedinclude_root = "https://raw.githubusercontent.com/10gen/docs-shared/main/"
Expand All @@ -27,7 +29,7 @@ full-version = "{+version-number+}.2"
version = "v{+version-number+}"
mdb-server = "MongoDB Server"
stable-api = "Stable API"
api = "https://mongodb.github.io/mongo-java-driver/{+version-number+}/apidocs/mongodb-driver-kotlin-sync"
api = "https://mongodb.github.io/mongo-java-driver/{+version-number+}/apidocs/mongodb-driver-kotlin-sync/mongodb-driver-kotlin-sync"
java-api = "https://mongodb.github.io/mongo-java-driver/{+version-number+}"
core-api = "{+java-api+}/apidocs/mongodb-driver-core/"
core-api = "{+java-api+}/apidocs/mongodb-driver-core"
kotlin-docs = "https://kotlinlang.org"
1,180 changes: 1,180 additions & 0 deletions source/agg-exp-ops.txt

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220 changes: 220 additions & 0 deletions source/aggregation.txt
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.. _kotlin-sync-aggregation:

====================================
Transform Your Data with Aggregation
====================================

.. facet::
:name: genre
:values: reference

.. meta::
:keywords: code example, transform, computed, pipeline
:description: Learn how to use the Kotlin Sync driver to perform aggregation operations.

.. contents:: On this page
:local:
:backlinks: none
:depth: 2
:class: singlecol

.. .. toctree::
.. :titlesonly:
.. :maxdepth: 1

.. /aggregation/aggregation-tutorials

Overview
--------

In this guide, you can learn how to use the {+driver-short+} to perform
**aggregation operations**.

You can use aggregation operations to process data in your MongoDB collections and
return computed results. The MongoDB Aggregation framework, which is
part of the Query API, is modeled on the concept of a data processing
pipeline. Documents enter a pipeline that contains one or more stages,
and each stage transforms the documents to output a final aggregated result.

You can think of an aggregation operation as similar to a car factory. A car factory has
an assembly line, which contains assembly stations with specialized
tools to do specific jobs, like drills and welders. Raw parts enter the
factory, and then the assembly line transforms and assembles them into a
finished product.

The **aggregation pipeline** is the assembly line, **aggregation stages** are the
assembly stations, and **operator expressions** are the
specialized tools.

Compare Aggregation and Find Operations
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

You can use find operations to perform the following actions:

- Select which documents to return
- Select which fields to return
- Sort the results

You can use aggregation operations to perform the following actions:

- Perform find operations
- Rename fields
- Calculate fields
- Summarize data
- Group values

Limitations
~~~~~~~~~~~

The following limitations apply when using aggregation operations:

- Returned documents must not violate the
:manual:`BSON document size limit </reference/limits/#mongodb-limit-BSON-Document-Size>`
of 16 megabytes.
- Pipeline stages have a memory limit of 100 megabytes by default. You can exceed this
limit by using the ``allowDiskUse()`` method from ``AggregateIterable`` class.

.. important:: $graphLookup exception

The :manual:`$graphLookup
</reference/operator/aggregation/graphLookup/>` stage has a strict
memory limit of 100 megabytes and ignores the ``allowDiskUse`` option.

Aggregation Example
-------------------

The examples in this section use the ``restaurants`` collection in the ``sample_restaurants``
database from the :atlas:`Atlas sample datasets </sample-data>`. To learn how to create a
free MongoDB Atlas cluster and load the sample datasets, see the
:atlas:`Get Started with Atlas </getting-started>` guide.

The following {+language+} data class models the documents in this collection:

.. literalinclude:: /includes/aggregation/aggregation.kt
:start-after: start-data-class
:end-before: end-data-class
:language: kotlin
:copyable:

Build and Execute an Aggregation Pipeline
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

To perform an aggregation on the documents in a collection, pass a list of aggregation
stages to the ``aggregate()`` method.

This example outputs a count of the number of bakeries in each borough
of New York City. The following code creates aggregation pipeline that contains the
following stages:

- A :manual:`$match </reference/operator/aggregation/match/>` stage to filter for documents
in which the value of the ``cuisine`` field is ``"Bakery"``.

- A :manual:`$group </reference/operator/aggregation/group/>` stage to group the matching
documents by the ``borough`` field, producing a count of documents for each distinct
value of that field.

.. TODO: uncomment when Aggregates Builder page is created

.. .. note::

.. The following example uses the builders pattern to implement the stages of an
.. aggregation pipeline. To learn more about how to use the builders pattern, see
.. :ref:`<aggregates-builders>`

.. io-code-block::

.. input:: /includes/aggregation/aggregation.kt
:language: kotlin
:start-after: start-aggregation-pipeline
:end-before: end-aggregation-pipeline
:dedent:

.. output::
:visible: false

Document{{_id=Bronx, count=71}}
Document{{_id=Manhattan, count=221}}
Document{{_id=Brooklyn, count=173}}
Document{{_id=Queens, count=204}}
Document{{_id=Staten Island, count=20}}
Document{{_id=Missing, count=2}}

.. tip::

When specifying a group key for the ``$group`` aggregation stage, ensure that you
escape any ``$`` characters by using the ``\`` character.

Explain an Aggregation
~~~~~~~~~~~~~~~~~~~~~~

To view information about how MongoDB executes your operation, you can
include the ``$explain`` aggregation stage in your pipeline. When MongoDB explains an
operation, it returns **execution plans** and performance statistics. An execution
plan is a potential way MongoDB can complete an operation.
When you instruct MongoDB to explain an operation, it returns both the
plan MongoDB selected for the operation and any rejected execution plans.

The following code example runs the same aggregation shown in the preceding section
and adds the ``$explain`` stage to output the operation details:

.. io-code-block::

.. input:: /includes/aggregation/aggregation.kt
:language: kotlin
:start-after: start-aggregation-explain
:end-before: end-aggregation-explain
:dedent:

.. output::
:visible: false

{
"explainVersion": "2",
"queryPlanner": {
"namespace": "sample_restaurants.restaurants"
"indexFilterSet": false,
"parsedQuery": {
"cuisine": {"$eq": "Bakery"}
},
"queryHash": "865F14C3",
"planCacheKey": "0697561B",
"optimizedPipeline": true,
"maxIndexedOrSolutionsReached": false,
"maxIndexedAndSolutionsReached": false,
"maxScansToExplodeReached": false,
"winningPlan": { ... }
...
}
...
}

Additional Information
----------------------

To view a full list of expression operators, see :manual:`Aggregation
Operators </reference/operator/aggregation/>` in the {+mdb-server+} manual.

To learn about assembling an aggregation pipeline and view examples, see
:manual:`Aggregation Pipeline </core/aggregation-pipeline/>` in the {+mdb-server+} manual.

To learn more about creating pipeline stages, see :manual:`Aggregation
Stages </reference/operator/aggregation-pipeline/>` in the {+mdb-server+} manual.

To learn more about explaining MongoDB operations, see
:manual:`Explain Output </reference/explain-results/>` and
:manual:`Query Plans </core/query-plans/>` in the {+mdb-server+} manual.

.. Aggregation Tutorials
.. ~~~~~~~~~~~~~~~~~~~~~

.. To view step-by-step explanations of common aggregation tasks, see
.. :ref:`kotlin-sync-aggregation-tutorials`.

API Documentation
~~~~~~~~~~~~~~~~~

For more information about executing aggregation operations with the {+driver-short+},
see the following API documentation:

- `aggregate() <{+api+}/com.mongodb.kotlin.client/-mongo-collection/aggregate.html>`__
- `AggregateIterable <{+api+}/com.mongodb.kotlin.client/-aggregate-iterable/index.html>`__
115 changes: 115 additions & 0 deletions source/builders.txt
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.. _kotlin-sync-builders:

=========================
Use Builders Code Pattern
=========================

.. contents:: On this page
:local:
:backlinks: none
:depth: 2
:class: singlecol

.. .. toctree::

.. /fundamentals/builders/aggregates
.. /fundamentals/builders/filters
.. /fundamentals/builders/indexes
.. /fundamentals/builders/projections
.. /fundamentals/builders/sort
.. /fundamentals/builders/updates

Overview
--------

This page describes how to use the various available builders in your code and describes
benefits of using the provided builders.

The {+driver-short+} provides type-safe builder classes and methods that enable developers to
efficiently build queries and aggregations.

Why Use Builders?
-----------------

If you use only plain {+language+} to construct BSON query documents, you are not
able to identify syntax errors until runtime. The builders help ensure the corretness of
syntax and can be less verbose than constructing BSON documents.

Example
-------

This section provides three equivalent ways to fetch the ``email`` field values of documents
in the ``users`` collection that meet the following criteria:

- ``gender`` value is ``"female"``
- ``age`` value is greater than ``29``

The following data class models the documents in the ``users`` collection:

.. literalinclude:: /includes/builders/builders.kt
:start-after: start-user-class
:end-before: end-user-class
:language: kotlin
:copyable:
:dedent:

The following data class models the results returned by our query:

.. literalinclude:: /includes/builders/builders.kt
:start-after: start-result-class
:end-before: end-result-class
:language: kotlin
:copyable:
:dedent:

MongoDB Query API
~~~~~~~~~~~~~~~~~

The following sample performs the query by using the MongoDB Query API:

.. code-block:: js

collection.find(
{ "gender": "female", "age" : { "$gt": 29 }},
{ "_id": 0, "email": 1 }
)

Document Class Filter
~~~~~~~~~~~~~~~~~~~~~

The following example performs the query by using the ``Document`` class to construct the
query filter:

.. literalinclude:: /includes/builders/builders.kt
:start-after: start-find
:end-before: end-find
:language: kotlin
:copyable:
:dedent:

Builders
~~~~~~~~

The following example performs the query by using the builder helpers:

.. literalinclude:: /includes/builders/builders.kt
:start-after: start-find-builders
:end-before: end-find-builders
:language: kotlin
:copyable:
:dedent:

.. TODO: Uncomment as pages get built

.. Available Builders
.. ------------------

.. The following pages describe how to implement the different classes of builders
.. available in the {+driver-short+}.

.. - :ref:`Aggregates <aggregates-builders>` for building aggregation pipelines.
.. - :ref:`Filters <filters-builders>` for building query filters.
.. - :ref:`Indexes <indexes-builders>` for creating index keys.
.. - :ref:`Projections <projections-builders>` for building projections.
.. - :ref:`Sorts <sorts-builders>` for building sort criteria.
.. - :ref:`Updates <updates-builders>` for building updates.
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