Re: Relationships across databases

From: Andrus Adamchik (andru..bjectstyle.org)
Date: Mon Jun 25 2007 - 04:34:48 EDT

  • Next message: Andrus Adamchik: "Re: Relationships across databases"

    I think the limitation has been mostly explained by others in this
    thread. So let me try to summarize:

            [works] Saving of related objects.
            [works] Resolving a relationship.
    [doesn't work] Doing a query on relationship source qualified on some
    criteria applied to the target objects.

    Andrus

    On Jun 21, 2007, at 12:07 AM, Øyvind Harboe wrote:
    > In the link below it says that relationships does not work across
    > databases "as it will require Cayenne to do in memory cartesian
    > product processing".
    >
    > What does this qualifier mean? Does it mean that it is possible to
    > enable this, but it would take a lot of memory? That this feature was
    > considered, but rejected as it would have not worked in all cases?
    >
    > For the cases that we need this, there is no problem for Cayenne to
    > have both tables completely in memory (always < 1000 records) so I'm
    > not concerned about CPU processing power or memory consumption.
    >
    > Has any work been done on supporting this?
    >
    >
    >
    > We've got a real database (Derby) that has relationships to other
    > existing datbases(MS Access/FoxPro databases). We can't move the
    > existing databases into Derby due to bug-by-bug compatibility
    > problems.
    >
    > http://cwiki.apache.org/CAY/multiple-databases-example.html
    >
    > --
    > Øyvind Harboe
    > http://www.zylin.com - eCos ARM & FPGA developer kit
    >



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