DOCS-10020 added comment param documentation to db.col.aggregate() and aggregate

Author: Pavithra Vetriselvan

source/includes/apiargs-dbcommand-aggregate-field.yaml

@@ -139,4 +139,19 @@ arg_name: field
 interface: dbcommand
 operation: aggregate
 position: 10
+---
+name: comment
+type: string
+optional: true
+description: |
+
+   Users can specify an arbitrary string to help trace the operation 
+   through the database profiler, currentOp, and logs.
+
+   .. versionadded:: 3.6
+
+arg_name: field
+interface: dbcommand
+operation: aggregate
+position: 11
 ...

source/includes/apiargs-method-db.collection.aggregate-options.yaml

@@ -85,5 +85,12 @@ source:
 interface: method
 operation: db.collection.aggregate
 position: 8
-
+---
+name: comment
+source:
+  ref: comment
+  file: apiargs-dbcommand-aggregate-field.yaml
+interface: method
+operation: db.collection.aggregate
+position: 9
 ...

source/reference/command/aggregate.txt

@@ -33,7 +33,8 @@ aggregate
         bypassDocumentValidation: <boolean>,
         readConcern: <document>,
         collation: <document>,
-        hint: <string or document>
+        hint: <string or document>,
+        comment: <string>
       }
 
    The :dbcommand:`aggregate` command takes the following fields as

source/reference/method/db.collection.aggregate.txt

@@ -297,3 +297,61 @@ majority of the nodes.
 
 .. [#agg-index-filters] :ref:`index-filters` can affect the choice of index
    used. See :ref:`index-filters` for details.
+
+Specify a Comment
+~~~~~~~~~~~~~~~
+
+A collection named ``movies`` contains documents formatted as such:
+
+.. code-block:: javascript
+
+  {
+    "_id" : ObjectId("599b3b54b8ffff5d1cd323d8"),
+    "title" : "Jaws",
+    "year" : 1975,
+    "imdb" : "tt0073195"
+  }
+
+The following aggregation operation finds movies created in 1995 and includes 
+the ``comment`` option to provide tracking information in the ``logs``, 
+the ``db.system.profile`` collection, and ``db.currentOp``.
+
+.. code-block:: javascript
+   db.movies.aggregate( [ { $match: { year : 1995 } } ], { comment : "match_all_movies_from_1995" } ).pretty()
+
+On a system with profiling enabled, you can then query the ``system.profile``
+collection to see all recent similar aggregations, as shown below:
+
+.. code-block:: javascript
+
+   db.system.profile.find( { "command.aggregate": "movies", "command.comment" : "match_all_movies_from_1995" } ).sort( { ts : -1 } ).pretty()
+
+This will return a set of profiler results in the following format:
+
+.. code-block:: javascript
+
+{
+  "op" : "command",
+  "ns" : "video.movies",
+  "command" : {
+    "aggregate" : "movies",
+    "pipeline" : [
+      {
+        "$match" : {
+          "year" : 1995
+        }
+      }
+    ],
+    "comment" : "match_all_movies_from_1995",
+    "cursor" : {
+      
+    },
+    "$db" : "video"
+  },
+  ...
+}
+
+An application can encode any arbitrary information in the comment in order 
+to more easily trace or identify specific operations through the system. 
+For instance, an application might attach a string comment incorporating its 
+process ID, thread ID, client hostname, and the user who issued the command.

source/release-notes/3.6.txt

@@ -64,6 +64,14 @@ option to specify the index to use.
    The ``hint`` does not apply to :pipeline:`$lookup` and
    :pipeline:`$graphLookup` stages.
 
+New ``comment`` Option
+~~~~~~~~~~~~~~~~~~~~~~
+
+:dbcommand:`aggregate` command and the
+:method:`db.collection.aggregate()` method support a new ``comment``
+option to help trace the operation through the database profiler, 
+currentOp, and logs.
+
 Support for Time Zones
 ~~~~~~~~~~~~~~~~~~~~~~
 
@@ -183,6 +191,8 @@ MongoDB 3.6 includes the following enhancements:
 - If authentication is turned on, you can only issue a :dbcommand:`getMore`
   against cursors you created.
 
+- 
+
 Changes Affecting Compatibility
 -------------------------------