> db.c.insert({a: [1, 2]})
WriteResult({ "nInserted" : 1 })
> db.c.find({a: {$lte: [0, 0]}})
> db.c.find({a: {$lte: [2, 2]}})
{ "_id" : ObjectId("5dfa766b191cd168059aaf54"), "a" : [ 1, 2 ] }
> db.c.createIndex({a: 1})
{
	"createdCollectionAutomatically" : false,
	"numIndexesBefore" : 1,
	"numIndexesAfter" : 2,
	"ok" : 1
}
> db.c.find({a: {$lte: [2, 2]}})
> 

{
	"queryPlanner" : {
		"plannerVersion" : 1,
		"namespace" : "test.c",
		"indexFilterSet" : false,
		"parsedQuery" : {
			"a" : {
				"$lte" : [
					2,
					2
				]
			}
		},
		"queryHash" : "811451DD",
		"planCacheKey" : "B859B02A",
		"winningPlan" : {
			"stage" : "FETCH",
			"filter" : {
				"a" : {
					"$lte" : [
						2,
						2
					]
				}
			},
			"inputStage" : {
				"stage" : "IXSCAN",
				"keyPattern" : {
					"a" : 1
				},
				"indexName" : "a_1",
				"isMultiKey" : true,
				"multiKeyPaths" : {
					"a" : [
						"a"
					]
				},
				"isUnique" : false,
				"isSparse" : false,
				"isPartial" : false,
				"indexVersion" : 2,
				"direction" : "forward",
				"indexBounds" : {
					"a" : [
						"[[], [ 2.0, 2.0 ]]"
					]
				}
			}
		},
		"rejectedPlans" : [ ]
	},
	"serverInfo" : {
		"host" : "borosaurus",
		"port" : 30000,
		"version" : "4.2.1",
		"gitVersion" : "edf6d45851c0b9ee15548f0f847df141764a317e"
	},
	"ok" : 1
}