DOCSP-17067 Expose usage stats for agg expressions

Author: mungitoperrito

source/reference/command/serverStatus.txt

@@ -4756,6 +4756,11 @@ metrics
             "scanAndOrder" : NumberLong(<num>),
             "writeConflicts" : NumberLong(<num>)
       },
+      "operatorCounters" : {
+            "expressions" : {
+               "<command>" : Long("0")
+            }
+      },
       "queryExecutor": {
             "scanned" : NumberLong(<num>),
             "scannedObjects" : NumberLong(<num>),
@@ -4863,6 +4868,22 @@ metrics
 
    *New in version 4.4 (4.2.6 and 4.0.19).* 
 
+.. serverstatus:: metrics.operatorCounters
+
+   A document with a number that indicates how often
+   :ref:`aggregation-expression-operators` ran. For some operators, the
+   number reported is a multiple of the times the operator actually
+   ran.
+
+   To get metrics for a specific operator, such as the greater-than
+   operator (:expression:`$gt`), append the operator to the command:
+
+   .. code-block:: javascript
+
+      db.runCommand( { serverStatus: 1 } ).metrics.operatorCounters.expressions.$gt
+
+   .. versionadded:: 5.0
+
 .. serverstatus:: metrics.commands
 
    A document that reports on the use of database commands. The fields

source/release-notes/5.0.txt

@@ -65,24 +65,24 @@ MongoDB 5.0 introduces the following aggregation operators:
      - Description
 
    * - :group:`$count`
-     - :group:`$count (aggregation accumulator) <$count>` 
+     - :group:`$count (aggregation accumulator) <$count>`
        provides a count of all documents when used in the existing
        pipeline :pipeline:`$group (aggregation) <$group>` stage and the
        new MongoDB 5.0 :pipeline:`$setWindowFields` stage.
 
        .. note:: Disambiguation
 
           The :group:`$count (aggregation accumulator) <$count>` is
-          distinct from the :pipeline:`$count (aggregation) <$count>` 
-          pipeline stage. 
+          distinct from the :pipeline:`$count (aggregation) <$count>`
+          pipeline stage.
 
    * - :expression:`$dateAdd`
      - Increments a :doc:`Date </reference/method/Date>` object by a
        specified number of time units.
 
    * - :expression:`$dateDiff`
      - Returns the difference between two dates.
-       
+
    * - :expression:`$dateSubtract`
      - Decrements a :doc:`Date </reference/method/Date>` object by a
        specified number of time units.
@@ -359,7 +359,7 @@ the ``"disabled"`` option.
 ``renameCollection`` Compatible with Sharded Collections
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-Starting in MongoDB 5.0, you can use the :dbcommand:`renameCollection` 
+Starting in MongoDB 5.0, you can use the :dbcommand:`renameCollection`
 command to change the name of a sharded collection.
 
 .. _5.0-rel-notes-shell:
@@ -374,15 +374,15 @@ The ``mongo`` shell has been deprecated in MongoDB v5.0. The
 replacement shell is :binary:`~bin.mongosh`. The legacy ``mongo`` shell
 will be removed in a future release.
 
-Shell packaging also changes in MongoDB v5.0. Refer to the 
+Shell packaging also changes in MongoDB v5.0. Refer to the
 :mongosh:`installation instructions </install>` for further details.
 
 Shell Support for GCP and Azure KMS Providers
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 Starting in MongoDB 5.0 (and MongoDB 4.4.5), the Google Cloud Platform
 KMS and Azure Key Vault are supported in both :binary:`~bin.mongosh`
-and the legacy :binary:`~bin.mongo` shell as 
+and the legacy :binary:`~bin.mongo` shell as
 :ref:`Key Management Service (KMS) <field-level-encryption-kms>`
 providers for :doc:`/core/security-client-side-encryption`.
 
@@ -442,12 +442,12 @@ Implicit Default Write Concern
 Audit Events
 ~~~~~~~~~~~~
 
-Starting in MongoDB 5.0, ``startup`` and ``logout`` audit action types 
-are available in 
+Starting in MongoDB 5.0, ``startup`` and ``logout`` audit action types
+are available in
 :doc:`System Event Audit Messages </reference/audit-message>`.
 
 The ``dropCollection`` audit action type (``atype``) adds an audit
-event when a :ref:`view <3.4-reference-views>` is dropped. 
+event when a :ref:`view <3.4-reference-views>` is dropped.
 
 ``mongosShutdownTimeoutMillisForSignaledShutdown`` Parameter
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -460,10 +460,10 @@ complete before initiating a shutdown of :binary:`~bin.mongos`.
 Configurable ``zstd`` Compression Level
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-MongoDB 5.0 introduces the 
+MongoDB 5.0 introduces the
 :setting:`~storage.wiredTiger.engineConfig.zstdCompressionLevel`
-configuration file option which allows for configurable compression 
-levels when 
+configuration file option which allows for configurable compression
+levels when
 :setting:`~storage.wiredTiger.collectionConfig.blockCompressor` is set
 to ``zstd``.
 
@@ -547,7 +547,7 @@ Previously, :dbcommand:`logRotate` would rotate the two logs together.
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 Starting in MongoDB 5.0, :ref:`slow operation
-<database-profiling-specify-slowms-threshold>` log messages include a 
+<database-profiling-specify-slowms-threshold>` log messages include a
 ``remote`` field specifying client IP address.
 
 Define Variables Using the ``let`` Option
@@ -610,10 +610,11 @@ Aggregation Metrics
   - :serverstatus:`metrics.commands.findAndModify.pipeline` *(Also available in 4.4.2+, 4.2.11+)*
   - :serverstatus:`metrics.commands.findAndModify.arrayFilters` *(Also available in 4.4.2+, 4.2.11+)*
   - :serverstatus:`metrics.dotsAndDollarsFields`
+  - :serverstatus:`metrics.operatorCounters`
 
 Replication Metrics
   - :serverstatus:`metrics.repl.reconfig.numAutoReconfigsForRemovalOfNewlyAddedFields`
-         
+
 Read Concern Counters
   - :serverstatus:`readConcernCounters`, which reports on the
     :ref:`read concern level <read-concern-levels>` specified by query
@@ -726,7 +727,7 @@ Upgrade Procedures
 ------------------
 
 .. important:: Feature Compatibility Version
-   
+
    To upgrade to MongoDB 5.0 from a 4.4 deployment, the 4.4 deployment
    must have ``featureCompatibilityVersion`` set to ``4.4``. To check
    the version: