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db.items.aggregate([{"$lookup":{"from":"Mapper","let":{"itemIndetifier":"$Identifier"},"pipeline":[{"$match":{"$expr":{"$eq":["$$itemIndetifier","$Identifier"]}}},{"$lookup":{"from":"Parent","let":{"type":"$Type"},"pipeline":[{"$match":{"$expr":{"$and":[{"$eq":["$ParentName","GP"]},{"$eq":["$$type","$Type"]}]}}}],"as":"joined1"}},{"$unwind":{"path":"$joined1","preserveNullAndEmptyArrays":true}}],"as":"joined2"}},{"$unwind":{"path":"$joined2"}},{"$project":{"_id":0,"Name":1,"Identifier":1,"Type":"$joined2.joined1.Type"}}])