DOCS-14048 mapReduce refactoring

Author: jason-price-mongodb

source/aggregation.txt

@@ -41,7 +41,7 @@ transforms the documents into an aggregated result. For example:
 
       <video style="width:100%;" src="_images/agg-pipeline.mp4" controls> </video>
 
-In the example,
+In the example:
 
 .. code-block:: javascript
 
@@ -82,28 +82,6 @@ internal optimization phase. See
 :ref:`aggregation-pipeline-operators-and-performance` and
 :doc:`/core/aggregation-pipeline-optimization` for details.
 
-.. _aggregation-map-reduce:
-
-Map-Reduce
-----------
-
-.. tip::
-
-   :doc:`Aggregation pipeline </core/aggregation-pipeline>`
-   provides better performance and a more coherent interface than
-   map-reduce.
-
-   For examples of aggregation alternatives to map-reduce operations,
-   see :doc:`/tutorial/map-reduce-examples`. See also
-   :doc:`/reference/map-reduce-to-aggregation-pipeline`.
-
-MongoDB also provides :doc:`map-reduce </core/map-reduce>` operations
-to perform aggregation. Map-reduce uses custom JavaScript functions to
-perform the map and reduce operations, as well as the optional
-*finalize* operation.
-
-.. include:: /images/map-reduce.rst
-
 .. _single-purpose-agg-operations:
 
 Single Purpose Aggregation Operations
@@ -114,11 +92,18 @@ MongoDB also provides :method:`db.collection.estimatedDocumentCount()`,
 
 All of these operations aggregate documents from a single collection.
 While these operations provide simple access to common aggregation
-processes, they lack the flexibility and capabilities of the
-aggregation pipeline and map-reduce.
+processes, they lack the flexibility and capabilities of an aggregation
+pipeline.
 
 .. include:: /images/distinct.rst
 
+.. _aggregation-map-reduce:
+
+Map-Reduce
+----------
+
+.. include:: /includes/fact-use-aggregation-not-map-reduce.rst
+
 Additional Features and Behaviors
 ---------------------------------
 

source/core/aggregation-pipeline.txt

@@ -29,7 +29,7 @@ results. For example:
 
       <video style="width:100%;" src="../_images/agg-pipeline.mp4" controls> </video>
 
-In the example,
+In the example:
 
 .. code-block:: javascript
 
@@ -53,8 +53,8 @@ Pipeline
 
 The MongoDB aggregation pipeline consists of :ref:`stages
 <aggregation-pipeline-operator-reference>`. Each stage transforms the
-documents as they pass through the pipeline. Pipeline stages do not
-need to produce one output document for every input document; e.g.,
+documents as they pass through the pipeline. Pipeline stages do not need
+to produce one output document for every input document. For example,
 some stages may generate new documents or filter out documents.
 
 Pipeline stages can appear multiple times in the pipeline with the
@@ -98,11 +98,11 @@ by the aggregation process with one exception: :ref:`accumulator
 <aggregation-accumulator-operators>` expressions.
 
 The accumulators, used in the :pipeline:`$group` stage, maintain their
-state (e.g. totals, maximums, minimums, and related data) as documents
-progress through the pipeline. Some accumulators are available in the
-:pipeline:`$project` stage; however, when used in the
-:pipeline:`$project` stage, the accumulators do not maintain their
-state across documents.
+state (for example, totals, maximums, minimums, and related data) as
+documents progress through the pipeline. Some accumulators are available
+in the :pipeline:`$project` stage; however, when used in the
+:pipeline:`$project` stage, the accumulators do not maintain their state
+across documents.
 
 Starting in version 4.4, MongoDB provides the :group:`$accumulator` and
 :expression:`$function` aggregation operators. These operators provide
@@ -194,41 +194,29 @@ pipeline.
 Considerations
 --------------
 
-Sharded Collections
-~~~~~~~~~~~~~~~~~~~~
+Aggregation Pipeline Limitations
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-The aggregation pipeline supports operations on sharded collections.
-See :ref:`aggregation-pipeline-sharded-collection`.
-
-Aggregation Pipeline vs Map-Reduce
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+An aggregation pipeline has some limitations on the value types and
+the result size. See :doc:`/core/aggregation-pipeline-limits`.
 
-The aggregation pipeline provides better performance and a more coherent
-interface than :doc:`map-reduce </core/map-reduce>`.
+Aggregation Pipeline Optimization
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-Various map-reduce operations can be rewritten using :doc:`aggregation
-pipeline operators </meta/aggregation-quick-reference>`, such as
-:pipeline:`$group`, :pipeline:`$merge`, etc. For map-reduce operations
-that require custom functionality, MongoDB provides the
-:group:`$accumulator` and :expression:`$function` aggregation operators
-starting in version 4.4. These operators provide users with the ability
-to define custom aggregation expressions in JavaScript.
+An aggregation pipeline has an internal optimization phase that provides
+improved performance for certain sequences of operators. See
+:doc:`/core/aggregation-pipeline-optimization`.
 
-See :doc:`/tutorial/map-reduce-examples` for details.
-
-Limitations
-~~~~~~~~~~~
+Aggregation on Sharded Collections
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-Aggregation pipeline have some limitations on value types and result
-size. See :doc:`/core/aggregation-pipeline-limits` for details on
-limits and restrictions on the aggregation pipeline.
+An aggregation pipeline supports operations on sharded collections.
+See :ref:`aggregation-pipeline-sharded-collection`.
 
-Pipeline Optimization
-~~~~~~~~~~~~~~~~~~~~~
+Aggregation Pipeline as an Alternative to Map-Reduce
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-The aggregation pipeline has an internal optimization phase that
-provides improved performance for certain sequences of operators. For
-details, see :doc:`/core/aggregation-pipeline-optimization`.
+.. include:: /includes/fact-use-aggregation-not-map-reduce.rst
 
 .. toctree::
    :titlesonly:

source/core/map-reduce-concurrency.txt

@@ -10,6 +10,11 @@ Map-Reduce Concurrency
    :depth: 1
    :class: singlecol
 
+.. admonition:: Aggregation Pipeline as an Alternative to Map-Reduce
+   :class: note
+
+   .. include:: /includes/fact-use-aggregation-not-map-reduce.rst
+
 The map-reduce operation is composed of many tasks, including reads
 from the input collection, executions of the ``map`` function,
 executions of the ``reduce`` function, writes to a temporary collection

source/core/map-reduce-sharded-collections.txt

@@ -10,6 +10,11 @@ Map-Reduce and Sharded Collections
    :depth: 1
    :class: singlecol
 
+.. admonition:: Aggregation Pipeline as an Alternative to Map-Reduce
+   :class: note
+
+   .. include:: /includes/fact-use-aggregation-not-map-reduce.rst
+
 Map-reduce supports operations on sharded collections, both as an input
 and as an output. This section describes the behaviors of
 :dbcommand:`mapReduce` specific to sharded collections.

source/core/map-reduce.txt

@@ -10,19 +10,10 @@ Map-Reduce
    :depth: 1
    :class: singlecol
 
-.. admonition:: Aggregation Pipeline as Alternative
+.. admonition:: Aggregation Pipeline as Alternative to Map-Reduce
    :class: note
 
-   :doc:`Aggregation pipeline </core/aggregation-pipeline>`
-   provides better performance and a more coherent interface than
-   map-reduce, and various map-reduce operations can be rewritten
-   using :doc:`aggregation pipeline operators
-   </meta/aggregation-quick-reference>`, such as :pipeline:`$group`,
-   :pipeline:`$merge`, :group:`$accumulator`, etc. 
-
-   For examples of aggregation alternatives to map-reduce operations,
-   see :doc:`/tutorial/map-reduce-examples`. See also
-   :doc:`/reference/map-reduce-to-aggregation-pipeline`.
+   .. include:: /includes/fact-use-aggregation-not-map-reduce.rst
 
 Map-reduce is a data processing paradigm for condensing large volumes
 of data into useful *aggregated* results. To perform map-reduce

source/includes/examples-map-reduce.rst

@@ -4,25 +4,10 @@ Map-Reduce Examples
 .. map-reduce-document-examples-begin
 .. map-reduce-document-prototype-begin
 
-.. admonition:: Aggregation Pipeline as Alternative
-   :class: note
-
-   :doc:`Aggregation pipeline </core/aggregation-pipeline>` provides
-   better performance and a simpler interface than map-reduce, and
-   map-reduce expressions can be rewritten using :doc:`aggregation
-   pipeline operators </meta/aggregation-quick-reference>` such as
-   :pipeline:`$group`, :pipeline:`$merge`, and others.
-   
-   For map-reduce expressions that require custom functionality, MongoDB
-   provides the :group:`$accumulator` and :expression:`$function`
-   aggregation operators starting in version 4.4. These operators
-   provide the ability to define custom aggregation expressions in
-   JavaScript.
-
-   The examples in this section include aggregation pipeline
-   alternatives without custom aggregation expressions. For alternatives
-   that use custom expressions, see :ref:`Map-Reduce to Aggregation
-   Pipeline Translation Examples <mr-to-agg-examples>`.
+The examples in this section include aggregation pipeline alternatives
+without custom aggregation expressions. For alternatives that use custom
+expressions, see :ref:`Map-Reduce to Aggregation Pipeline Translation
+Examples <mr-to-agg-examples>`.
 
 Create a sample collection ``orders`` with these documents:
 

source/includes/fact-use-aggregation-not-map-reduce.rst

@@ -0,0 +1,16 @@
+An :doc:`aggregation pipeline </core/aggregation-pipeline>` provides
+better performance and usability than a :doc:`map-reduce
+</core/map-reduce>` operation.
+
+Map-reduce operations can be rewritten using :doc:`aggregation pipeline
+operators </meta/aggregation-quick-reference>`, such as
+:pipeline:`$group`, :pipeline:`$merge`, and others. 
+
+For map-reduce operations that require custom functionality, MongoDB
+provides the :group:`$accumulator` and :expression:`$function`
+aggregation operators starting in version 4.4. Use these operators to
+define custom aggregation expressions in JavaScript.
+
+For examples of aggregation pipeline alternatives to map-reduce
+operations, see :doc:`/reference/map-reduce-to-aggregation-pipeline` and
+:doc:`/tutorial/map-reduce-examples`.

source/reference/aggregation-commands-comparison.txt

@@ -10,18 +10,10 @@ Aggregation Commands Comparison
    :depth: 1
    :class: singlecol
 
-.. tip::
+.. admonition:: Aggregation Pipeline as Alternative to Map-Reduce
+   :class: note
 
-   Starting in version 4.4, MongoDB adds the :group:`$accumulator` and
-   :expression:`$function` aggregation operators. Using
-   :group:`$accumulator` and :expression:`$function` ,
-   :dbcommand:`mapReduce` expressions can be re-written using the
-   aggregation operators.
-
-   Even before version 4.4, some map-reduce expressions could also be
-   rewritten using :doc:`other aggregation pipeline operators
-   </meta/aggregation-quick-reference>`, such as :pipeline:`$group`,
-   :pipeline:`$merge`, etc.
+   .. include:: /includes/fact-use-aggregation-not-map-reduce.rst
 
 Aggregation Commands Comparison Table
 -------------------------------------
@@ -47,7 +39,7 @@ MongoDB aggregation commands.
 
        Uses a "pipeline" approach where objects are transformed as they
        pass through a series of pipeline operators such as
-       :pipeline:`$group`,  :pipeline:`$match`, and :pipeline:`$sort`.
+       :pipeline:`$group`, :pipeline:`$match`, and :pipeline:`$sort`.
 
        See :doc:`/reference/operator/aggregation` for more information
        on the pipeline operators.

source/reference/command/mapReduce.txt

@@ -10,10 +10,10 @@ mapReduce
    :depth: 1
    :class: singlecol
 
-.. admonition:: Deprecated
-   :class: warning
+.. admonition:: Aggregation Pipeline as Alternative to Map-Reduce
+   :class: note
 
-   .. include:: /includes/5.0-mapReduce-deprecated.rst
+   .. include:: /includes/fact-use-aggregation-not-map-reduce.rst
 
 Definition
 ----------
@@ -22,26 +22,6 @@ Definition
 
    The :dbcommand:`mapReduce` command allows you to run
    :term:`map-reduce` aggregation operations over a collection. 
-   
-   .. admonition:: Aggregation Pipeline as Alternative
-      :class: note
-
-      :doc:`Aggregation pipeline </core/aggregation-pipeline>`
-      provides better performance and a simpler interface than
-      map-reduce, and map-reduce expressions can be
-      rewritten using :doc:`aggregation pipeline operators
-      </meta/aggregation-quick-reference>`, such as :pipeline:`$group`,
-      :pipeline:`$merge`, and so on. 
-   
-      For map-reduce expressions that require custom functionality,
-      MongoDB provides the :group:`$accumulator` and
-      :expression:`$function` aggregation operators starting in version
-      4.4. These operators provide users with the ability to define custom
-      aggregation expressions in JavaScript.
-
-      For examples of aggregation alternatives to map-reduce operations,
-      see :doc:`/tutorial/map-reduce-examples`. See also
-      :doc:`/reference/map-reduce-to-aggregation-pipeline`.
 
 Syntax
 ------

source/reference/map-reduce-to-aggregation-pipeline.txt

@@ -4,20 +4,21 @@ Map-Reduce to Aggregation Pipeline
 
 .. default-domain:: mongodb
 
-Starting in version 4.4, MongoDB adds the :group:`$accumulator` and
-:expression:`$function` aggregation operators. These operators provide
-users the ability to define custom aggregation expressions. Using these
-operations, the map-reduce expressions can be approximately re-written
-as in the following table.
+An :doc:`aggregation pipeline </core/aggregation-pipeline>` provides
+better performance and usability than a :doc:`map-reduce
+</core/map-reduce>` operation.
 
-.. note::
+Map-reduce operations can be rewritten using :doc:`aggregation pipeline
+operators </meta/aggregation-quick-reference>`, such as
+:pipeline:`$group`, :pipeline:`$merge`, and others. 
 
-   Various map-reduce expressions can be rewritten using
-   :doc:`aggregation pipeline operators
-   </meta/aggregation-quick-reference>`, such as :pipeline:`$group`,
-   :pipeline:`$merge`, etc., without requiring custom functions.
+For map-reduce operations that require custom functionality, MongoDB
+provides the :group:`$accumulator` and :expression:`$function`
+aggregation operators starting in version 4.4. Use these operators to
+define custom aggregation expressions in JavaScript.
 
-   For examples, see :doc:`/tutorial/map-reduce-examples`.
+Map-reduce expressions can be re-written as shown in the following
+sections.
 
 Map-Reduce to Aggregation Pipeline Translation Table
 ----------------------------------------------------
@@ -250,9 +251,9 @@ Examples
 
 Various map-reduce expressions can be rewritten using :doc:`aggregation
 pipeline operators </meta/aggregation-quick-reference>`, such as
-:pipeline:`$group`, :pipeline:`$merge`, etc., without requiring custom
-functions. However, for illustrative purposes, the following examples
-provide both alternatives.
+:pipeline:`$group`, :pipeline:`$merge`, and others, without requiring
+custom functions. However, for illustrative purposes, the following
+examples provide both alternatives.
 
 .. _mr-to-agg-examples1: