> db.test.find()
{ "_id" : ObjectId("5aa9341ad89e0643662e2f30"), "a" : { "$minKey" : 1 } }
> db.test.getIndexes()
[
	{
		"v" : 2,
		"key" : {
			"_id" : 1
		},
		"name" : "_id_",
		"ns" : "test.test"
	}
]
> db.test.find({a: {$gt: MinKey}})
> db.test.createIndex({a: 1})
{
	"createdCollectionAutomatically" : false,
	"numIndexesBefore" : 1,
	"numIndexesAfter" : 2,
	"ok" : 1
}
> db.test.find({a: {$gt: MinKey}})
{ "_id" : ObjectId("5aa9341ad89e0643662e2f30"), "a" : { "$minKey" : 1 } }