Hi, David!
SCOCollection.add() may be implemented with lazy
feature, and you're right at this point. However,
convinience is also a concern for me. Since I had
noted the bi-directional attribute for a collection in
the metadata, I should be allowed to modify one side
of them and let the impl. do the last. As I said.
--- David Bullock <[EMAIL PROTECTED]> wrote:
> Bin Sun wrote:
>
> >Hi, David!
> >
> > I'd like to share some of my ideas. We are
> >developing heavy stressed web applications based on
> >JDO. In each bi-di-relation, if the coder has to
> >assign both sides, the other side(usually a
> >collection) has to be loaded into memory and cause
> >much performance penalty. It's more efficient to
> leave
> >this synchronization task to the implementation.
> >
> >
>
> Hi Bin,
>
> Thanks for your sharing your experiences. This is
> what I was wanting -
> a justification from a real live user!
>
> But I have a quibble with your statement: "if the
> coder has to assign
> both sides, the other side (usually a collection)
> has to be loaded into
> memory".
>
> So you're saying that if I have persistent objects
> just so:
>
> public class Invoice {
> private Set<Line> lines;
> public void addLine(Line line) {
> this.lines.add(line);
> }
> }
>
> public class Line {
> private Invoice invoice;
> public void setInvoice(Invoice invoice) {
> this.invoice = invoice;
> }
> }
>
> and I do this:
>
> static {
> Invoice invoice =
> Util.getPersistentInvoice("1234");
> Line line = new Line();
>
> line.setInvoice(invoice):
> invoice.addLine(line); /*expensive?*/
> }
>
> that the JDO impl necessarily fetches the entire
> contents of the
> Invoice.lines collection? And *because* of this
> problem, you as a user
> wish to avoid the invoice.addLine(line) call?
>
> I guess there might be JDO impl's out there which do
> that. But I'd
> rather pay money for a good one [1] which allowed me
> to control the
> fetch policy. There's absolutely no reason why the
> JDO impl needs to go
> to the database to let me invoke .add() on a SCO
> collection, until it
> needs to flush and do an INSERT.
>
> Hence there is no performance hit when setting both
> sides 'manually'.
>
> Please hasten to correct me if I've misunderstood
> why the performance
> hit takes place.
>
> cheers,
> David.
>
>
> [1] Not that there are many takers for my money
> anymore since JSR 220
> 'took over' persistence.
>
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