Hi Josh,
Assuming (and this assumption is a bit dodgy) "weight" is stored for
CarAddedParts and CarModelInfo, and that the weight of a given car =
CarModelInfo.weight + all CarAddedParts.weight
Long customerId = new Long(1);
Criteria c1 = new Criteria();
c.addEqualTo("carModelInfo.carInfo.invoice.customer.id", customerId);
Collection parts = QueryByCriteria(CarAddedParts.class, c);
Criteria c2 = new Criteria();
c.addEqualTo("carInfo.invoice.customer.id", customerId);
Collection models = QueryByCriteria(CarModelInfo.class, c);
BigDecimal totalParts = new BigDecimal("0");
for (Iterator it = parts.iterator(); iter.hasNext();) {
CarAddedPart part = (CarAddedPart) it.next();
totalParts = totalParts.add(part.getWeight);
}
BigDecimal totalModels = new BigDecimal("0");
for (Iterator it = models.iterator(); iter.hasNext();) {
CarInfoModel model = (CarInfoModel) it.next();
totalModels = totalModels.add(model.getWeight);
}
BigDecimal totalWeight = totalParts.add(totalWeights);
Ron's just replied with an equally sensible solution; seeing how I've just
spent 5 mins working this out, I thought I'd press send anyway.
Cheers,
Charles.
>-----Original Message-----
>From: Josh Berry [mailto:[EMAIL PROTECTED]
>Sent: 10 July 2003 17:30
>To: [EMAIL PROTECTED]
>Subject: Optimization advice/help.
>
>
>I don't want this to just be a performance question, but I
>must admit that
>that is at the heart of my problem.
>
>First, a little background on my problem. I will try to work
>this into a
>standard shopping cart/customer problem, but it may prove difficult.
>
>So... Lets say I have the following classes:
>
> *Customer
> A person buying a car. Obviously many of these exist.
> *Invoice
> An individual record of a single customer buying one or more cars.
> Many of these can exist per customer.
> *CarInfo
> A total breakdown of a vehicle to be ordered.
> *CarMakeInfo
> Basic information on a broad category of vehicle. (e.g.
>Ford Mustang)
> *CarModelInfo
> Specific information on a vehicle.
> (e.g. 4.0 liter engine, manual locks, dimensions, etc.)
> *CarCustomizationsInfo
> Any special changes that a customer requested for the vehicle.
> This is basically a set of overrides to CarModelInfo. So, either
> it exists or it does not.
> (e.g. Dimensions changed due to added roof lights,
> power locks added.)
> *CarAddedParts
> Any of a number of additional items to be added to the vehicle.
> (e.g. the roof lights )
>
>
>Now... I believe these will be all that is needed.
>
>The relationships are as follows.
>
> Customer has a 1:M with Invoice.
> Invoice has a 1:M with CarInfo.
> CarInfo has a 1:1 with CarMakeInfo.
> CarInfo has a 1:1 with CarModelInfo.
> CarInfo has a 1:1 with CarCustomizationsInfo.
> CarInfo has a 1:M with CarAddedPartsInfo.
>
>
>So, the problem I have is this:
>
>We currently do reports where we need to know the total weight
>of everything a
>customer has ever ordered. Now, it is clean code with OJB, as
>I can just loop
>through all of a customer's invoices calling getWeight for
>every CarInfo.
>However, this has performed abysmally slowly.
>
>Now, my guess is that OJB does one select to get all of the
>Invoices. Then,
>it will do another select per Invoice to get all of the CarInfos.
>Then, for each CarInfo, it will do 3 selects to get each of
>CarMakeInfo,
>CarModelInfo, and CarCustomizationsInfo.
>In addition, it will do another select per CarInfo to get
>CarAddedPartsInfo.
>
>For a single customer with X invoices averaging Y CarInfos that have on
>average Z CarAddedParts, this yields approximately 1 + X + (4
>* Y) selects.
>Obviously, this is a lot of selects to happen once you start
>doing this over
>many Invoices that have many CarInfos with lots of AddedParts.
> And when my
>numbers average to something like 1000 invoices with about 80
>parts a piece,
>this starts getting out of hand quickly.
>
>So, the problem I am facing is I do not know a way to avoid
>all of these
>selects with OJB. Writing it on my own, I am able to reduce
>the number down
>to a fixed 4 selects. I could probably widdle it down more,
>but I would
>prefer some maintainability of the code, which is why I would
>like to keep
>OJB. Does anyone know of any tricks?
>
>Basically, I think my problem is when you have a M:N:O
>relationship that needs
>to be looped through. (Also note: in the actual problem I have, I have
>several of these relationships in existance. Think of it as
>though I had
>seperate cases for Cars and Trucks, with a few differences
>between them.)
>
>Finally, I thank anyone who had the patience to read through
>this example and
>question. Hopefully, I made it simple enough to make sense
>without being
>useless.
>
>Thanks,
>
>-josh
>
>
>
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