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From Borut Bolčina <...@najdi.si>
Subject Re: Parent/Child Insert ordering (was: Caching problem?)
Date Mon, 09 Oct 2006 13:43:47 GMT
Hi,

in API docs for org.objectstyle.cayenne.map.AshwoodEntitySorter it says:

    "...Presently it works for acyclic database schemas with possible
    multi-reflexive tables. The class uses topological sorting from the
    Ashwood library <http://objectstyle.org/ashwood/>."

What are multi-reflexive tables? I guess not every reflexive 
relationship is cyclic. If db row "points" to the same db row then it 
would be cyclic (for example - someone is his/her own manager), 
otherwise just reflexive. Is this correct?

-Borut

On 21.5.2006 19:24, 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 <jdevries@pfrog.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.
>>
>>
>

-- 
bLOG <http://www.delo.si/blog/borutb/>
--
Naključna *izjava tedna* iz tednika Mladina:

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