Hello,
I have a business entity named ChargeActivity, and I am not using second level caching nor am I using query caching. I fetch an object of ChargeActivity as

Ilist result = _session.CreateQuery(Predicate).SetCacheable(false).List();

No I go the database an fire a query and change one of the column against charge activty and now I again call

Ilist result = _session.CreateQuery(Predicate).SetCacheable(false).List();

unfortunately I don't get the updates. But I see that NHibernate fires query to the database.

In file Loader.cs , there is one method as
DoQuery(ISessionImplementor session,QueryParameters queryParameters,bool returnProxies)

In this methods there is one statement as
IDataReader rs = GetResultSet(st, selection, session);

Which actualy fires the query and gets the updated result in variable rs.

But further there is call to method GetRowFromResultSet which in turn calls method GetRow, and in method GetRow

it checks whether the object already exists in the cache(first level) and returns if found, therefore updates are not available

obj = session.GetEntity(key);
if (obj != null)
{
//its already loaded so dont need to hydrate it
InstanceAlreadyLoaded(rs, i, persisters[i], key, obj, lockModes[i], session);
}
else
{
obj = InstanceNotYetLoaded(rs, i, persisters[i], key, lockModes[i], optionalObjectKey, optionalObject, hydratedObjects,session);
}

return obj;


Why does it fire query to database and also check whether the object is in local cache? Also even if the object exists in the local cache it is not updated with the result set newly fetched from the database.
Can someone please help?

I'm not 100 percent sure, but try to eplain what happens. You load the objects in a session and keep that session. When you query for the second time, hibernate has to query the database since there could be new/deleted objectes. After retrieving the object hibernate checks if the objects are already in the session, which they are. Changes to the objects are only detected, if you have a version or timestamp column specified in the mapping, which I suppose you don't have. So hibernate thinks the objects are the same and does neither create new objects nor update the exisiting ones.

There are two ways to prevent that. One is using a version or timestamp column, the other is do a session.Refresh(obj). The latter will work for the already loaded object, but you won't see new/deleted objects.

Thanks for your reply.
I have a couple of question :
What does version and timestamp stand for?
And where do we set this?

Both are columns/properties which keep track of the state of a an object. Have a look at the documentation:

http://www.hibernate.org/hib_docs/nhibernate/1.2/reference/en/html/mapping.html#mapping-declaration-version

http://www.hibernate.org/hib_docs/nhibernate/1.2/reference/en/html/manipulatingdata.html#manipulatingdata-updating

I am a bit confused

should the declaration be as


<class name="FIG.FIGMD.BusinessEntities.ViewChargeActivityDetails,FIG.FIGMD.BusinessEntities" table="ViewChargeActivityDetails" lazy="false" dynamic-update="true">
<id name="ChargeActivityUid" column="ChargeActivityUid" type="Guid">
<generator class="assigned"/>
</id>

<version column="ModifiedDate" name="ModifiedDate" type="timestamp"/>

<property column="ModifiedDate" type="DateTime" name="ModifiedDate" />
</class>


OR Should it be as



<class name="FIG.FIGMD.BusinessEntities.ViewChargeActivityDetails,FIG.FIGMD.BusinessEntities" table="ViewChargeActivityDetails" lazy="false" dynamic-update="true">
<id name="ChargeActivityUid" column="ChargeActivityUid" type="Guid">
<generator class="assigned"/>
</id>



<property column="ModifiedDate" type="DateTime" name="ModifiedDate"
<version column="ModifiedDate" name="ModifiedDate" type="timestamp"/>
/property>
</class>

I would say just the version, no additonal property, since the version mapping already specifies the property.

I think I have confused you too,
In the first example <version> is child to <class>, whereas in the second one it's child to <property>.

Which one is correct ? is it a class level attribute or property level.

class level

btw. you can put the nhibernate schema definitions in C:\Program Files\Microsoft Visual Studio 8\Xml\Schemas and you will get intelli sense for the mappings. Saves you a lot of time and lookup.

I tried this, but didn't work

<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2">
<class name="FIG.FIGMD.BusinessEntities.ChargeActivity,FIG.FIGMD.BusinessEntities" table="ChargeActivity" lazy="false" dynamic-update="true">

<id name="ChargeActivityUid" column="ChargeActivityUid" type="Guid">
<generator class="assigned"/>
</id>

<version column="ModifiedDate" name="ModifiedDate" type="Timestamp"/>
<!--<timestamp column="ModifiedDate" name="ModifiedDate" access="property" />-->

<property column="TicketNumber" type="String" name="TicketNumber" length="50" />
</class>
</hibernate-mapping>


<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2">
<class name="FIG.FIGMD.BusinessEntities.ChargeActivity,FIG.FIGMD.BusinessEntities" table="ChargeActivity" lazy="false" dynamic-update="true">

<id name="ChargeActivityUid" column="ChargeActivityUid" type="Guid">
<generator class="assigned"/>
</id>

<timestamp column="ModifiedDate" name="ModifiedDate" access="property" />

<property column="TicketNumber" type="String" name="TicketNumber" length="50" />
</class>
</hibernate-mapping>



Any Idea?

What do you mean with "didn't work" ? Do you still have the same problem as in your initial post ?

Yes I queried the same object , in the same session but didn't get any updates While modifying the row in database I had also updated column ModifiedDate.

If that's still the case, I'm afraid my assumption that version/timestamp would solve that problem were wrong :-(. Checkout chapter 10 (http://www.hibernate.org/hib_docs/nhibernate/1.2/reference/en/html/transactions.html), maybe you find some hints there.

Another possibility if you only want to reload the already loaded objects is to call session.Refresh() on these objects.

Thanks for all your help. If <timestamp> and <version> foes not work,
then how does NHibernate handle changes made by other users in distributed enviorement. Suppose I fetch an object of Order and within next few seconds the same object is modified by some other user using NHibernate or directly through database, now until I use the same session I will always get the older version.