Question

I’m just getting started with db4o in a scheduling application and I’m looking for an efficient way to retrieve rooms which are not booked between certain dates.

So, I have a collection of Room objects each of which has a collection of Booking objects (which can be empty). A Booking has a start date and and end date. I want to say ‘get all the rooms that have no Bookings between DateA and DateB’.

I’m sure I could do this using a Native Query but since there’s a date range involved (my understanding is date ranges aren’t optimzed for NQ) and I need to do this query very frequently (many times per second for potentially more 10,000 rooms – the majority of which have no Bookings) I’m looking for more efficient alternatives.

Is there a way to phrase this using SODA?
Or a better way to arrange my data model to get round this issue?

Answer 1

Yes you can do this by using SODA Query

Date fromDate = null ; // assign reservation start dat
Date toDate = null ; // assign reservation upto
Query query = db.query();
query.constrain(Booking.class);
query.descend ("fromDate").constrain ( fromDate ).greater().equal ().
      and (query.descend ("toDate").constrain (toDate).smaller().equal());
ObjectSet<Booking> objectSet = query.execute();

Query for all of the rooms which do not have a booking between fromDate and toDate

 Query query = db.query();
query.constrain(Room.class);
query.descend ("bookingStartDate").constrain ( fromDate ).greater().equal ().and
(query.descend ("bookingEndDate").constrain (toDate).smaller().equal()).not();
ObjectSet<Room> objectSet = query.execute();

See Also : Building SODA Queries