I would like to set the default transaction level to ReadCommitted in my Fluent NHibernate configuration. If I were using XML mapping files, I could add a key to my config file:
<add key="hibernate.connection.isolation" value="ReadCommitted" />
but I can't figure out how to accomplish this with Fluent configuration.
Fluent NHibernate doesn't do anything with the transaction isolation, so the default will be whatever NHibernate defaults to. I don't know off the top of my head what that is.
We don't have an explicit method to set the isolation, but as it's just a configuration value you can use the Raw method to set the property.
MsSqlConfiguration.MsSql2008.Raw("connection.isolation", "isolation_level");
Source: https://web.archive.org/web/20100812054505/http://support.fluentnhibernate.org/discussions/help/45-default-isolation-level-for-transactions
You should specify isolation level, when calling: BeginTransaction on your Session object.
...
ISession session = SessionFactory.OpenSession();
session.BeginTransaction(IsolationLevel.ReadCommitted);
...
Please refer to: NHibernate transactions for more details.
With Fluent NHibernate v 2.x IsolationLevel() method can be used to globally set isolation level for transactions:
MsSqlConfiguration.MsSql2008
.IsolationLevel(System.Data.IsolationLevel.ReadCommitted)
Related
I have noticed, by using log4net, that when calling ISession.Update, it updates all the changed objects.
For example:
// Change 2 instances
user1.IsDeleted = true;
user2.UserName = "Xyz";
// Call session.Update to update the 2 users
using (ITransaction transaction = session.BeginTransaction())
{
Session.Update(user1); // This updates both user1 & user2
transaction.Commit();
}
using (ITransaction transaction = session.BeginTransaction())
{
Session.Update(user2); // Now there is no need for this
transaction.Commit();
}
Is this the default behavior of NHibernate or has something to do with my mapping file?
Can I make NHibernate update one by one?
It's the normal and default behavior:
Hibernate maintains a cache of Objects
that have been inserted, updated or
deleted. It also maintains a cache of
Objects that have been queried from
the database. These Objects are
referred to as persistent Objects as
long as the EntityManager that was
used to fetch them is still active.
What this means is that any changes to
these Objects within the bounds of a
transaction are automatically
persisted when the transaction is
committed. These updates are implicit
within the boundary of the transaction
and you don’t have to explicitly call
any method to persist the values.
From Hibernate Pitfalls part 2:
Q) Do I still have to do Save and
Update inside transactions?
Save() is only needed for objects that
are not persistent (such as new
objects). You can use Update to bring
an object that has been evicted back
into a session.
From NHibernate's automatic (dirty checking) update behaviour:
I've just discovered that if I get an
object from an NHibernate session and
change a property on object,
NHibernate will automatically update
the object on commit without me
calling Session.Update(myObj)!
Answer: You can set Session.FlushMode to
FlushMode.Never. This will make your
operations explicit ie: on tx.Commit() or session.Flush().
Of course this will still update the
database upon commit/flush. If you do
not want this behavior, then call
session.Evict(yourObj) and it will
then become transient and NHibernate
will not issue any db commands for it.
This is the default behavior when FlushMode of session is Auto or Commit.
In these cases calling transaction.Commit() flushes the session & updates ALL persistent objects
So if you remove the calls Session.Update it wouldn't make any difference
Can I make NHibernate update one by one?
Yes. use FlushMode.Never or postpone commiting the session if possible. I guess you don't need to use Evict for this case
After I retrieve an entity, I change a property of it.
Then I retrieve the same entity.
How do I say Nhibernate, that it shall update the entity before it loads the entity?
Here the code:
EmployeeRepository employeeRepository = new EmployeeRepository();
Employee employee = employeeRepository.GetById(4);
employee.LastName = "TEST!!!";
Employee employee2 = employeeRepository.GetById(4);
Currently Nhibernate don't make an update in my program. I thought just setting the FlushMode to Auto will update the entity automatically.
EDIT
The background is that I try to reprdouce this behaviour in another application.
There is NO save method! Just this code. The NHibernate version is really old, it is version 1.2.1.4000. maybe there is the catch.
When I set the FlushMode in the brownfield application to Commit then no update statement is generated.
But in my own project I still can not reproduce this "automatic" behaviour.
Are both calls to the employeeRepository ultimately using the same NHibernate ISession instance? If so, then they will return the same object, and the updated LastName value will be reflected. If not, then you will need to make sure you are disposing your ISession instance each time to take advantage of auto flushing.
According to the documentation for the default FlushMode of Auto:
The ISession is sometimes flushed
before query execution in order to
ensure that queries never return stale
state. This is the default flush mode.
So you have to manually flush the session to ensure that your changes are persisted before reading the object again.
EmployeeRepository employeeRepository = new EmployeeRepository();
Employee employee = employeeRepository.GetById(4);
employee.LastName = "TEST!!!";
session.Flush();
Employee employee2 = employeeRepository.GetById(4);
If your repository is using the same ISession for both calls (as it should imo) then employee 4 will be retrieved from the cache and have the change. However, the change will not have been persisted to the database yet.
If your repository GetById methods uses a new session for each call then it will always hit the database to retrieve the employee. If you're disposing of the session in the method then your objects are returned as detached from a session. This strategy defeats the purpose of NHibernate and relegates it to a simple data access tool.
I have an entity which is updated externally (using triggers, stored procedures). This means the entity can change without my knowledge in the same session, and it is required for me that I always perform a database hit, and never use the entity from the first level cache.
Is this possible using NHibernate (or actually, Castle ActiveRecord)?
You cold use a IStatelessSession instead of ISession to disable first level cache:
using (ISessionFactory sf = cfg.BuildSessionFactory())
using (IStatelessSession session = sf.OpenStatelessSession())
{
// ...
}
I have been successfully using NHibernate, but now I am trying to move to Fluent NHibernate. I have created all of my mapping files and set up my session manager to use a Fluent Configuration. I then run my application and it runs successfully, but no data is returned.
There are no errors or any indication that there is a problem, but nothing runs.
when using NHibernate, if I don't set my hbm xml files as an embedded resource, this same thing happens. This makes me wonder what I have to set my Map classes to. Right now, they are just set to Compile, and they are compiled into the dll, which I can see by disassembling it.
Does anyone have any thoughts as to what may be happening here?
Thanks
private ISessionFactory GetSessionFactory()
{
return Fluently.Configure()
.Database(
IfxOdbcConfiguration
.Informix1000
.ConnectionString("Provider=Ifxoledbc.2;Password=mypass;Persist Security Info=True;User ID=myuser;Data Source=mysource")
.Dialect<InformixDialect1000>()
.ProxyFactoryFactory<ProxyFactoryFactory>()
.Driver<OleDbDriver>()
.ShowSql()
)
.Mappings(
x => x.FluentMappings.AddFromAssembly(System.Reflection.Assembly.GetExecutingAssembly())
//.ExportTo("C:\\mappings")
)
.BuildSessionFactory();
}
Does the executing assembly contain the fluent mapping classes? I would try:
.Mappings(x => x.FluentMappings.AddFromAssemblyOf<MappedType>())
Where MappedType is a class that has a fluent mapping.
They should just be set to compile, that's fine. Nothing special needed here. The problem is most likely in your fluent configuration rather than the mapping.
I am performing a standard update in NHibernate to a single property. However on commit of the transaction the sql update seems to set all fields I have mapped on the table even though they have not changed. Surely this can't be normal behaviour in Nhibernate? Am I doing something wrong? Thanks
using (var session = sessionFactory.OpenSession())
{
using (var transaction = session.BeginTransaction())
{
var singleMeeting = session.Load<Meeting>(10193);
singleMeeting.Subject = "This is a test 2";
transaction.Commit();
}
}
This is the normal behavior. You can try adding dynamic-update="true" to your class definition to override this behavior.
Well. yes this is normal behaviour for NHibernate. You can use generated attribute for your properties to change the behaviour. Details on Ayende's blog.
Why is this default is because with dynamics you don't get your query plan cached. And usually you don't mind that you send few more bytes over high speed network connection between your application server and database. Unless you are saving long strings where this setting is perfectly appropriate.