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    Type:Task 
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    Resolution: Fixed
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    Priority:Major - P3 
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    Affects Version/s: None
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    Component/s: None
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The format of an Aggregate Explain response has been changed.
Before we had:
{
	"stages": [{
			"$cursor": {
				"query": {},
				"fields": {
					"x": 1,
					"_id": 1
				},
				"queryPlanner": {
					"plannerVersion": 1,
					"namespace": "Tests11051524.MongoCollectionTests",
					"indexFilterSet": false,
					"parsedQuery": {},
					"queryHash": "8B3D4AB8",
					"planCacheKey": "8B3D4AB8",
					"winningPlan": {
						"stage": "COLLSCAN",
						"direction": "forward"
					},
					"rejectedPlans": []
				}
			}
		}, {
			"$project": {
				"_id": true,
				"x": "$x"
			}
		}
	],
	"ok": 1.0
}
, but now all latests servers return:
{
	"queryPlanner": {
		"plannerVersion": 1,
		"namespace": "Tests11051512.MongoCollectionTests",
		"indexFilterSet": false,
		"parsedQuery": {},
		"queryHash": "8B3D4AB8",
		"planCacheKey": "8B3D4AB8",
		"optimizedPipeline": true,
		"winningPlan": {
			"stage": "PROJECTION_DEFAULT",
			"transformBy": {
				"_id": true,
				"x": "$x"
			},
			"inputStage": {
				"stage": "COLLSCAN",
				"direction": "forward"
			}
		},
		"rejectedPlans": []
	},
	"serverInfo": {
		"host": "EPBYMINW3653",
		"port": 27017,
		"version": "4.3.0-2014-g8010c51",
		"gitVersion": "8010c51d3f1cc1020959f8b351f8242d141d42a3"
	},
	"ok": 1.0
}
can be related to this ticket: https://jira.mongodb.org/browse/SERVER-38691