[{version:"1.002",subVersion:"3"}]

db.collection.aggregate([{"$set":{"version":{"$let":{"vars":{"splitVer":{"$map":{"input":{"$split":["$version","."]},"as":"strNum","in":{"$toInt":"$$strNum"}}}},"in":{"version1":{"$first":"$$splitVer"},"version2":{"$last":"$$splitVer"},"version3":{"$toInt":"$subVersion"}}}},"subVersion":"$$REMOVE"}}])