Good question :-) Andriy, our math geek, is no longer with us. I
don't recall the details (need to dig through Ashwood I guess), but
simple parent/child relationships within the same table used to work
afaik... We may think of smarter strategies to resolve the cycles
(such as a chain of insert/update queries in the same transaction)...
I don't think this will happen soon though.
Andrus
On Oct 9, 2006, at 9:43 AM, Borut Bolčina wrote:
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."
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 <[EMAIL PROTECTED]> 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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