DOCS-14899 BACKPORT DOCS-14715 (#558)

Author: Dave

source/reference/command/serverStatus.txt

@@ -4024,6 +4024,11 @@ metrics
             "scanAndOrder" : NumberLong(<num>),
             "writeConflicts" : NumberLong(<num>)
       },
+      "operatorCounters" : {
+            "match" : {
+               "<command>" : Long(<num>)
+            }
+      },
       "queryExecutor": {
             "scanned" : NumberLong(<num>),
             "scannedObjects" : NumberLong(<num>),
@@ -4127,6 +4132,37 @@ metrics
 
    *New in version 4.4 (4.2.6 and 4.0.19).* 
 
+.. serverstatus:: metrics.operatorCounters.match
+
+   A document with a number that indicates how often
+   :ref:`match expressions <query-projection-operators-top>` ran. For
+   some operators, the number reported is a multiple of the times the
+   operator actually ran.
+
+   :ref:`Match expression operators <query-projection-operators-top>`
+   also increment as part of an aggregation pipeline :pipeline:`$match`
+   stage. If the ``$match`` stage uses the :query:`$expr` operator, the
+   counter for ``$expr`` increments, but the component counters do not
+   increment. 
+
+   Consider the following query: 
+
+   .. code-block:: javascript
+      :copyable: false
+
+      db.matchCount.aggregate(
+         [
+            { $match:
+               {  $expr: { $gt: [ "$_id", 0 ] } }
+            }
+         ]
+      )
+
+   The counter for ``$expr`` increments when the query runs. The
+   counter for ``$gt`` does not. 
+
+   .. versionadded:: 4.4.11
+
 .. serverstatus:: metrics.commands
 
    A document that reports on the use of database commands. The fields