Re: Parent/Child Insert ordering (was: Caching problem?)

From: Jeff de Vries (jdevrie..frog.com)
Date: Mon May 22 2006 - 16:43:28 EDT

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    Setting INITIALLY DEFERRED and DEFERRABLE seems to work (now).

    Thanks!
    Jeff

    On May 21, 2006, at 12:12 PM, Jeff de Vries wrote:

    > Going back and looking at my code, I see that a two step commit is
    > fine in this particular case since the initially committed items
    > can stand on their own without any inconsistencies. I'll try
    > setting the INITIALLY DEFERRED and DEFERRABLE constraints anyway to
    > see what happens.
    >
    > Andrus Adamchik wrote:
    >> Cayenne handles correct ordering of operations automatically,
    >> based on dependencies derived from relationships.The algorithm has
    >> a few limitations though. It can't handle cycles (when Entity A
    >> depends on Entity B, but also Entity B depends on Entity A). This
    >> probably also includes entities that have relationships to the
    >> same entity (I assume this is the case the original post was
    >> referring to).
    >>
    >> There are few solutions:
    >>
    >> 1. (a workaround, rather than a solution) Do commit in two steps.
    >> 2. Define FK constraints in question as DEFERRABLE and INITIALLY
    >> DEFERRED (supported by Postgres 8.*)
    >> 3. Set a custom org.objectstyle.cayenne.map.EntitySorter on the
    >> DataNode.
    >>
    >> Andrus
    >>
    >>
    >> On May 20, 2006, at 3:00 AM, Marcin Skladaniec wrote:
    >>
    >>> Hm. Strange. I do really complex commits, sometimes 7 or more
    >>> related records (I mean 7 levels of relationship, not seven
    >>> entities), related by many-to-many many-to-one relationships and
    >>> never get those problems. And it doesn't matter if the records
    >>> are new or old. Could you describe how you are creating objects
    >>> and how do you commit them ?
    >>>
    >>> Regards
    >>> Marcin
    >>>
    >>> On 20/05/2006, at 4:31 PM, Tomi NA wrote:
    >>>
    >>>> On 5/20/06, Jeff de Vries <jdevrie..frog.com> wrote:
    >>>>> I don't know if it is related or not, but I've also had
    >>>>> problems in the
    >>>>> past when I try to create a new parent and several child
    >>>>> objects related
    >>>>> to that parent all at once and then try to commit. The problem
    >>>>> looks
    >>>>> like Cayenne is INSERTing the child records into the database
    >>>>> first,
    >>>>> before the parent record, and the database complains that the
    >>>>> children
    >>>>> have an invalid foreign key (and, yes, I have the ON UPDATE and ON
    >>>>> DELETE rules for the foreign key set to DO NOTHING and I still
    >>>>> get the
    >>>>> error from PostgreSQL). To get around it I just committed the
    >>>>> parent
    >>>>> first, then committed all the children.
    >>>>
    >>>> I had the same problem, IIRC: I was very surprised that cayenne
    >>>> couldn't handle such a commit, although truth be told, I can't
    >>>> imagine
    >>>> everything that's going on under the hood of the operation that
    >>>> would
    >>>> make implementing this feature difficult.
    >>>> I would certainly love to see this fixed (if at all possible) as I
    >>>> wasn't to happy to have to commit in the middle of what had to
    >>>> be an
    >>>> atomic transaction. It'd also make the framework a lot more
    >>>> flexible,
    >>>> e.g. enabling the user to have long inter-commit sessions with
    >>>> complex
    >>>> data updates, if the user so desires.
    >>>>
    >>>> t.n.a.
    >>>
    >>>
    >>



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