Well, yes it is possible up to a point.
Usually it is through the "to-many" relationship I get my objects.
Some other times it might be through a custom query meaning I have to
do it each time.
However, as I said in the second email I sent about prefetching, the
solution is maybe the following:
@SuppressWarnings("unchecked")
public List<Role> getRoles () {
if
(org
.apache
.cayenne.Fault.class.isInstance(this.readPropertyDirectly("roles"))) {
Expression exp = ExpressionFactory.matchExp("person", this);
SelectQuery query = new SelectQuery(Role.class, exp);
query.addPrefetch("profile");
query.addPrefetch("person");
List<Role> roles = getObjectContext().performQuery(query);
ToManyList tml = new ToManyList(this,"roles");
tml.addAll(roles);
writePropertyDirectly("roles",tml);
}
return super.getRoles();
}
The advantage of this is that it does the prefetch but also sets
correctly the "to-many" relationship, meaning it will not refetch
everything if I do an addToRoles or removeFromRoles.
If I want to refault the relationship, I do:
if
(org
.apache
.cayenne
.access
.ToManyList.class.isInstance(this.readPropertyDirectly("roles"))) {
((org.apache.cayenne.access.ToManyList)getRoles()).invalidate();
}
Is this the correct way of doing it?
If so, could there be a way to add this in a generic way to the model?
Now, it would still be cool if we could have batch faulting for the
odd places where we didn't set up the prefetching.
Alex
Le 14 nov. 07 à 14:45, Andrus Adamchik a écrit :
Can you use prefetching instead? You got a list of users vis some
sort of query - just add prefetch to that query.
Andrus
On Nov 14, 2007, at 8:11 AM, Alexander Lamb (dev) wrote:
Hello list,
One thing is killing performance of our application: it is the
resolving of individual to-one faults in lists.
For example, we can have 200 roles each refering to a person.
When we loop through the roles, for each role where we do a
role.getPerson() there will be a return trip to the database.
In the EOF days, there was a possibility to define a batch faulting
strategy for the entity. In that we would say for example "batch
fault 20 for person" and the first time a to-one fault to person
from role would be found, it would look in the data context for up
to 19 more to build a single SQL statement and fetch in one go the
person objects and resolve up to 20 faults.
Is this feature available somewhere in Cayenne 3m2 or planned in
the near future?
If not, is there some kind of callback or hook wich would allow us
to do the same thing?
Thanks,
Alex
