Fabio, you're absolutely right. I meant winform application in my
example. I know that bigint has a lot of room but what about saving
trips to the database.
I have not looked at the HiLo implementation in NH but I think what is
happening is that the SessionFactory is keeping the count of the last
used id per table. so from the above example:
using (var session = SessionSource.CreateSession())
{
using (session.BeginTransaction())
{
var customer = new Customer("Joe");
// this is asking the session factory for the next id
// the sesion factory has nothing so it increments the next_hi
in the database and returns 1001
session.SaveOrUpdate(customer);
var customer2 = new Customer("Shmoe");
// this time the session factory has an availabe id value for
the Customer entity type
// and returns 1002
session.SaveOrUpdate(customer2);
var employee = new Employee("Jack");
// for this entity type the session factory has no value and it
has to increment the next_hi in the database
// and return 2001
session.SaveOrUpdate(employee);
}
}
I think this is not only inefficient but unnecessarily complicated and
this complexity effects generating id values outside NH (you have to
think about SSIS packages and what not). I think an easier and more
effiect alternative if the SessionFactory does not keep track of id
per table but per database. This way the third call to save the
employee will return 1003 instead of 2002 and save a trip to the
database and use less keys. In addition it is easier to implement
outside NH because it doesn't have to know about the table it is
accessing.
On Sep 14, 6:09 pm, Fabio Maulo <[email protected]> wrote:
> btw Delucia that is an improvement of HighLow defined in ORM theory.The
> target of the improvement is : has a less fragmentation per table.
>
> In winform and 2 physical tiers you should use a little max-low (like 99)
>
> 2009/9/14 Delucia <[email protected]>
>
>
>
>
>
> > Currently if I want to insert an object graph that has 2 entities that use
> > HiLo for their Id, NH session will go to the database for two times, one
> > time for each entity, and increment the next_hi count. I was assuming that
> > the session will have to go once to the database and reserve a range to be
> > used for all entities since all entities are using the same next_hi value
> > that will guarantee they will not collide. here is an example:
> > using (var session = SessionSource.CreateSession())
> > {
>
> > using (session.BeginTransaction())
> > {
> > var customer = new Customer("Joe");
>
> > session.SaveOrUpdate(customer);
>
> > var employee = new Employee { FirstName = "Sue",
> > LastName = "Wong" };
>
> > session.SaveOrUpdate(employee);
> > }
>
> > session.Transaction.Commit();
> > }
> > }
>
> > Given the max_Lo is set to 1000, this code will go to the database twice to
> > increment the next_hi one time for the customer and one time for the
> > employee. I think it should increment it only once per session.
>
> --
> Fabio Maulo- Hide quoted text -
>
> - Show quoted text -
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