[{_id:1,"_a":[{"_aId":{"CC":"CA"},"_p":[{"_pId":{"CC":"CA","SN":1},"s":{"c":{"t":[{sId:1,language:"CA",format:"A4"},{sId:2,language:"JP",format:"A4"}]},"a":{"t":[{sId:4,language:"CA","format":"A4"},{sId:5,language:"EN","format":"A3"}]},"d":{"t":[{sId:10,language:"CA","format":"A4"}]}}},{"_pId":{"CC":"CA","SN":2},"s":{"c":{"t":[{sId:1,language:"CA",format:"A4"},{sId:2,language:"JP",format:"A4"}]},"a":{"t":[{sId:4,language:"CA","format":"A4"},{sId:5,language:"EN","format":"A3"}]},"d":{"t":[{sId:10,language:"CA","format":"A4"}]}}}]}]}]

db.collection.aggregate([{$match:{"_a._p._pId.CC":"CA"}},{$project:{_id:0,_aId:"$_a._aId",_a:{$reduce:{input:"$_a",initialValue:[],in:{$concatArrays:["$$value",{$map:{input:{$filter:{input:"$$this._p",cond:{$eq:["$$this._pId.CC","CA"]}}},as:"i",in:{"$mergeObjects":["$$i",{_aId:"$$this._aId"}]}}}]}}}}},{$project:{_a:{$reduce:{input:"$_a",initialValue:[],in:{$concatArrays:["$$value",{$map:{input:{$reduce:{input:{$objectToArray:"$$this.s"},initialValue:[],in:{$concatArrays:["$$value",{$filter:{input:"$$this.v.t",cond:{$and:[{$eq:["$$this.format","A4"]},{$eq:["$$this.language","CA"]}]}}}]}}},as:"p",in:{_aId:"$$this._aId",_pId:"$$this._pId",sId:"$$p.sId"}}}]}}}}},{$unwind:"$_a"},{$replaceRoot:{newRoot:"$_a"}}])