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Cost Analysis Rule-of-Thumb Guidelines

Cost Analysis Rule-of-Thumb Guidelines. As a guide, consider denormalizing if: redundancy is minimal and update anomalies are not expected (e.g., StreetNr City State  Zip) replicated objects are large (e.g., images in View)

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Cost Analysis Rule-of-Thumb Guidelines

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  1. Cost AnalysisRule-of-Thumb Guidelines • As a guide, consider denormalizing if: • redundancy is minimal and update anomalies are not expected (e.g., StreetNr City State  Zip) • replicated objects are large (e.g., images in View) • join frequencies are very high when compared to updates (e.g., approximate cost in Canadian dollars) • Using actual application characteristics, estimate space and time requirements for various possibilities and compare costs.

  2. Cost Estimation (Space) Assume: 5 rooms, 100 reservations, and 80 guests. 54 = 20 804 = 320 1004 = 400 740 54 = 20 1007 = 700 720 804 = 320 1007 = 700 1020 10010 = 1000 Case 1: Room(RoomNr, RoomName, NrBeds, Cost) Guest(GuestNr, GuestName, StreetNr, City) Reservation(GuestNr, RoomNr, ArrivalDate, NrDays) vs. Case 2: Room(RoomNr, RoomName, NrBeds, Cost) Reservation(GuestNr, GuestName, StreetNr, City, RoomNr, ArrivalDate, NrDays) vs. Case 3: Guest(GuestNr, GuestName, StreetNr, City) Reservation(GuestNr, RoomNr, ArrivalDate, NrDays, RoomName, NrBeds, Cost) vs. Case 4: Reservation(GuestNr, GuestName, StreetNr, City, RoomNr, ArrivalDate, NrDays, RoomName, NrBeds, Cost)

  3. Cost Estimation (Time) Case 1: Room(RoomNr, RoomName, NrBeds, Cost) Guest(GuestNr, GuestName, StreetNr, City) Reservation(GuestNr, RoomNr, ArrivalDate, NrDays) vs. Case 2: Room(RoomNr, RoomName, NrBeds, Cost) Reservation(GuestNr, GuestName, StreetNr, City, RoomNr, ArrivalDate, NrDays) Most important queries/updates: 1. (40%) What rooms are available? 2. (30%) Make a reservation. 3. (10%) Change a reservation. 4. (10%) Cancel a reservation. 5. (the rest) Miscellaneous. Assume indexed on primary keys. 1. Case 1 & 2: Using the Reservation table, retrieve reservations that could overlap the requested date and determine room availability. (Case 1 insignificantly betterthe only difference is that Case 1 transfers fewer values in its records.) …

  4. Semantic Change? Case 1: Room(RoomNr, RoomName, NrBeds, Cost) Guest(GuestNr, GuestName, StreetNr, City) Reservation(GuestNr, RoomNr, ArrivalDate, NrDays) vs. Case 2: Room(RoomNr, RoomName, NrBeds, Cost) Reservation(GuestNr, GuestName, StreetNr, City, RoomNr, ArrivalDate, NrDays) Most important queries/updates: ... 2. (30%) Make a reservation. ... Assume indexed on primary keys. 2. Case 1: Insert tuple in Reservation (1 read & 1 write) and insert tuple in Guest, if necessary, (1 read and (usually) 1 write). Case 2: Insert tuple in Reservation (1 read & 1 write); check duplicate guest information (read file, or add secondary index). (Developer) Do we really need to check duplicate guest information? (Proprietor) Hmmm, maybe not; it doesn’t matter if it is different. (Developer) Does a guest always need the same guest number? (Proprietor) Not really; there are no guest numbers in our manual system. (Developer) Aha! Great, this really lets us savewatch this.

  5. Unique GuestNr in Reservation Observe that we have a new set of keys: { {GuestNr}, {RoomNr, ArrivalDate} } And thus a new generated database scheme: Reservation(GuestNr, GuestName, City, Street, RoomNr, ArrivalDate, NrDays) Room(RoomNr, RoomName, NrBeds, Cost)

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