MONGOID-4848 Add server 4.4 configurations to evergreen (#4769)

* MONGOID-4848 Add server 4.4 configurations to evergreen

* fix map/reduce tests

* pend map/reduce code and code w/scope tests

* fix the sharding test on 4.4

* remove testing_replica_set?

* Document map/reduce raw results and statistics

Co-authored-by: Oleg Pudeyev <[email protected]>

Author: p-mongo

source/tutorials/mongoid-queries.txt

@@ -1656,6 +1656,72 @@ Valid options to ``#out`` are:
 - ``reduce: "name"``: Store in a collection with the
   provided name, and reduce all existing results in that collection.
 
+Raw Results
+-----------
+
+Results of Map/Reduce execution can be retrieved via the ``execute`` method
+or its aliases ``raw`` and ``results``:
+
+.. code-block:: ruby
+
+  mr = Band.where(:likes.gt => 100).map_reduce(map, reduce).out(inline: 1)
+  
+  mr.execute
+  # => {"results"=>[{"_id"=>"Tool", "value"=>{"likes"=>200.0}}],
+        "timeMillis"=>14,
+        "counts"=>{"input"=>4, "emit"=>4, "reduce"=>1, "output"=>1},
+        "ok"=>1.0,
+        "$clusterTime"=>{"clusterTime"=>#<BSON::Timestamp:0x00005633c2c2ad20 @seconds=1590105400, @increment=1>, "signature"=>{"hash"=><BSON::Binary:0x12240 type=generic data=0x0000000000000000...>, "keyId"=>0}},
+        "operationTime"=>#<BSON::Timestamp:0x00005633c2c2aaf0 @seconds=1590105400, @increment=1>}
+
+
+Statistics
+----------
+
+MongoDB servers 4.2 and lower provide Map/Reduce execution statistics. As of
+MongoDB 4.4, Map/Reduce is implemented via the aggregation pipeline and
+statistics described in this section are not available.
+
+The following methods are provided on the ``MapReduce`` object:
+
+- ``counts``: Number of documents read, emitted, reduced and output through
+  the pipeline.
+- ``input``, ``emitted``, ``reduced``, ``output``: individual count methods.
+  Note that ``emitted`` and ``reduced`` methods are named differently from
+  hash keys in ``counts``.
+- ``time``: The time, in milliseconds, that Map/Reduce pipeline took to execute.
+
+The following code illustrates retrieving the statistics:
+
+.. code-block:: ruby
+
+  mr = Band.where(:likes.gt => 100).map_reduce(map, reduce).out(inline: 1)
+  
+  mr.counts
+  # => {"input"=>4, "emit"=>4, "reduce"=>1, "output"=>1}
+  
+  mr.input
+  # => 4
+  
+  mr.emitted
+  # => 4
+  
+  mr.reduced
+  # => 1
+  
+  mr.output
+  # => 1
+  
+  mr.time
+  # => 14
+
+.. note::
+
+  Each statistics method invocation re-executes the Map/Reduce pipeline.
+  The results of execution are not stored by Mongoid. Consider using the
+  ``execute`` method to retrieve the raw results and obtaining the statistics
+  from the raw results if multiple statistics are desired.
+
 
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