[{"_id":ObjectId("5c05984246a0201286d4b57a"),f:"x","_a":[{"_onlineStore":{}},{"_p":{"s":{"a":{"t":[{"dateP":"20200-09-20","l":"English","size":"XXL"}]},"c":{"t":[{"dateP":"20300-09-20","l":"English","size":"XXL"}]}}}}]}]

db.collection.aggregate([{$unwind:"$_a"},{$project:{_id:0,f:1,data:{$objectToArray:"$_a._p.s"}}},{$unwind:"$data"},{$unwind:"$data.v.t"},{$match:{$expr:{$gt:[{$strLenCP:"$data.v.t.dateP"},10]}}},{$project:{f:1,dateP:"$data.v.t.dateP",t:"$data.k"}}])