> for (var i = 0; i < 5000; ++i) { var arr = []; for (var j = 0; j < 10; ++j) { arr.push({n: "prop" + j, v: Math.floor(Math.random() * 1000) }) }; db.generic.insert({props: arr}) }
> db.generic.findOne()
{
  "_id": ObjectId("515dd3b4f0bd676b816aa9b0"),
  "props": [
    {
      "n": "prop0",
      "v": 40
    },
    {
      "n": "prop1",
      "v": 198
    },
...
    {
      "n": "prop9",
      "v": 652
    }
  ]
}
> db.generic.ensureIndex({"props.n": 1, "props.v": 1})

> db.generic.find({props:{$elemMatch:{n:'prop1', v:800}}}).explain()
{
	"cursor" : "BtreeCursor props.n_1_props.v_1",
	"isMultiKey" : true,
	"n" : 143,
	"nscannedObjects" : 143,
	"nscanned" : 143,
	"nscannedObjectsAllPlans" : 143,
	"nscannedAllPlans" : 143,
	"scanAndOrder" : false,
	"indexOnly" : false,
	"nYields" : 0,
	"nChunkSkips" : 0,
	"millis" : 11,
	"indexBounds" : {
		"props.n" : [
			[
				"prop1",
				"prop1"
			]
		],
		"props.v" : [
			[
				800,
				800
			]
		]
	},
	"server" : "agmac.local:27017"
}

> db.generic.find({props:{$elemMatch:{n:'prop1', v:{$gt:800, $lt: 1000}}}}).explain()
{
	"cursor" : "BtreeCursor props.n_1_props.v_1",
	"isMultiKey" : true,
	"n" : 25287,
	"nscannedObjects" : 25287,
	"nscanned" : 25287,
	"nscannedObjectsAllPlans" : 25287,
	"nscannedAllPlans" : 25287,
	"scanAndOrder" : false,
	"indexOnly" : false,
	"nYields" : 0,
	"nChunkSkips" : 0,
	"millis" : 114,
	"indexBounds" : {
		"props.n" : [
			[
				"prop1",
				"prop1"
			]
		],
		"props.v" : [
			[
				800,
				1.7976931348623157e+308
			]
		]
	},
	"server" : "agmac.local:27017"
}

> db.generic.find({props:{$elemMatch:{n:'prop1', v:{$elemMatch: {$gt:800, $lt: 1000}}}}}).explain()
{
	"cursor" : "BtreeCursor props.n_1_props.v_1",
	"isMultiKey" : true,
	"n" : 0,
	"nscannedObjects" : 25287,
	"nscanned" : 25287,
	"nscannedObjectsAllPlans" : 25287,
	"nscannedAllPlans" : 25287,
	"scanAndOrder" : false,
	"indexOnly" : false,
	"nYields" : 0,
	"nChunkSkips" : 0,
	"millis" : 224,
	"indexBounds" : {
		"props.n" : [
			[
				"prop1",
				"prop1"
			]
		],
		"props.v" : [
			[
				800,
				1000
			]
		]
	},
	"server" : "agmac.local:27017"
}