db={users:[{_id:1,name:"John",basketId:4},{_id:2,name:"mari",basketId:9},{_id:3,name:"tedd",basketId:32},{_id:4,name:"sara",basketId:14},{_id:5,name:"jane",basketId:3},],baskets:[{_id:1,items:0},{_id:2,items:2},{_id:3,items:0},{_id:4,items:0},{_id:5,items:7},{_id:9,items:1}]}

db.users.aggregate([{$lookup:{from:"baskets",localField:"basketId",foreignField:"_id",as:"basket"}},{$match:{$expr:{$gt:[{$first:"$basket.items"},0]}}}])