db.venues.aggregate(
	[
		{
			$match: {
			
			}
		},
		{
			$lookup: {
			    "from" : "tasks",
			    "as" : "foreign",
			    let: { localField: "$_id"},
			    "pipeline":[
						{
							"$match":{
								"$expr":{
									"$eq":["$v","$$localField"]
								}
							}
						},
						{"$limit":1},
						{"$count":"count"}
					]
			}
		},
		{
			$match: {"foreign.count":1}
		},
		{
			$count: "count"
		},
	],

	// Options
	{
		cursor: {
			batchSize: 50
		}
	}
);