I have an object model where a Calendar object has an IDictionary<MembershipUser, Perms> called UserPermissions, where MembershipUser is an object, and Perms is a simple enumeration. This is in the mapping file for Calendar as
<map name="UserPermissions" table="CalendarUserPermissions" lazy="true" cascade="all">
<key column="CalendarID"/>
<index-many-to-many class="MembershipUser" column="UserGUID" />
<element column="Permissions" type="CalendarPermission" not-null="true" />
</map>
Now I want to execute a query to find all calendars for which a given user has some permission defined. The permission is irrelevant; I just want a list of the calendars where a given user is present as a key in the UserPermissions dictionary. I have the username property, not a MembershipUser object. How do I build that using QBC (or HQL)? Here's what I've tried:
ISession session = SessionManager.CurrentSession;
ICriteria calCrit = session.CreateCriteria<Calendar>();
ICriteria userCrit = calCrit.CreateCriteria("UserPermissions.indices");
userCrit.Add(Expression.Eq("Username", username));
return calCrit.List<Calendar>();
This constructed invalid SQL -- the WHERE clause contained WHERE membership1_.Username = #p0 as expected, but the FROM clause didn't include the MemberhipUsers table.
Also, I really had to struggle to learn about the .indices notation. I found it by digging through the NHibernate source code, and saw that there's also .elements and some other dotted notations. Where's a reference to the allowed syntax of an association path? I feel like what's above is very close, and just missing something simple.
Just trying to do this myself and it looks like this can be done with HQL but not the Criteria API.
https://nhibernate.jira.com/browse/NH-1795
To do it in HQL:
http://ayende.com/Blog/archive/2009/06/03/nhibernate-mapping-ndash-ltmapgt.aspx
Specifically look for Ayende's comment:
It is something like:
select 1 from Profile p join p.Entries e
where index(e) = 'HasCats' and e = 'true'
Related
I'm new to Nhibernate. My problem is that I want to narrow down a query by using a column that is not included in my entity (ie hbm). I want to do something like this:
Session.QueryOver<MyEntity>()
.SQL_Where("MyFlag = 1")
Since I have no use of that flag later I don't want to include it to the entity
I know I can use:
Session
.CreateSQLQuery("SELECT A,B,C FROM ENTITY WHERE MyFlag = 1")
.SetResultTransformer(Transformers.AliasToBean<MyEntity>())
.List<MyEntity>();
It would be nice to use QueryOver<>(), it's more safe if a column is added etc.
You may be able to use filters:-
Put a filter on your mappings class definition, however this will affect ALL returned rows
e.g.
<class name="Domain.Model.MyEntity, Domain.Model" table="MyTable"
where="(MyFlag=1)">
...
</class>
or it may be possible to use conditional filters with QueryOver
<filter-def name="SetMyFlag">
<filter-param name=":flag" type="System.Int"/>
</filter-def>
<class name="Domain.Model.MyEntity, Domain.Model" table="MyTable">
...
<filter name="SetMyFlag" condition="(MyFlag=:flag)"/>
</class>
and use:-
session.EnableFilter("SetMyFlag").SetParameter("flag", 1);
session.QueryOver<MyEntity>();
Although I have never use conditional filters with unmapped columns so this may not work!
I'm very new to NHibernate so this may be fairly trivial, but searching is leaving me confused.
I have an AddOnAmount table as follows:
AddOnID | AddOnTypeID | Period | Amount
where AddOnTypeID is a FK. The rows have a unique constraint on AddOnTypeID and Period.
The mapping looks like this:
<id name="Id" column="AddOnId" type="long">
<generator class="native" />
</id>
<many-to-one name="AddOnType" column="AddOnTypeID" class="AddOnTypeStatic" not-null="true" />
<property name="Period" />
etc.
The AddOnTypeStatic class/table just has an Id, which is the numerical value stored on the table, and a descriptive Name.
I'm trying to write a query that will search by AddOnTypeId and Period, so I can validate the existence (or not) of a row before attempting to add a duplicate from my front end, but I'm not sure how to do that as the AddOnAmountStatic class has a subclass whereas the table has just an Id.
So far I've written:
public AddOnAmountStatic FindByAddOnTypeAndPeriod(long addOnType, string period)
{
return FindOne(CreateCriteria()
.Add(Restrictions.Eq("AddOnTypeId", addOnType))
.Add(Restrictions.Eq("Period", period))
.SetCacheable(true));
}
which does not work, as AddOnTypeId isn't a property of AddOnAmountStatic. Not sure how to access the property of the subclass in this context.
My mapping works, as I've been using it so far with no problems.
Solved my problem - it was simple but thought I'd add the solution here in case it helps anyone else.
I'd been thinking of constructing the query from the table's perspective (i.e., with the AddOnTypeID), whereas what I should have done is look at it from the entity's perspective. In other words, I just needed to pass in an AddOnTypeStatic object.
What I did was take my AddOnTypeID parameter, check it exists through NHibernate (returning either an AddOnTypeStatic object or null) then passed that through to the original query. Final query is simply
return FindOne(CreateCriteria()
.Add(Restrictions.Eq("AddOnType", addOnType))
.(Restrictions.Eq("Period", period))
.SetCacheable(true));
Hope this helps another newbie!
I have a recursive one-to-many relationship that has the default lazy value of true. What code can I write against the NH API that will efficiently retrieve the ENTIRE tree AS IF I had lazy="false" on the SubCategories mapping?
Here's the recursive one-to-many relationship:
<class name="Category" lazy="false">
...
<list name="SubCategories" fetch="subselect">
<key column="ParentCategoryID"/>
<index column="PositionInList"/>
<one-to-many class="Category"/>
</list>
I don't specify lazy="false" on the list since laziness is required in about half the queries I need to run. I have fetch="subselect" on the list as an optimization for when I do manage to retrieve the entire tree.
I've tried the ICriteria API:
session.CreateCriteria<Category>().SetFetchMode( "SubCategories", FetchMode.Eager ).Add( Restrictions.IsNull("ParentCategory") ).SetResultTransformer( CriteriaSpecification.DistinctRootEntity ).List<Category>();
but that only eagerly loaded only the first level in the hierarchy.
See Ayende's site: Efficiently Selecting a Tree. I have successfully used this technique in my own applications. With ICriteria, it looks like this:
session.CreateCriteria<Category>()
.SetFetchMode("SubCategories", FetchMode.Join)
.SetResultTransformer(new DistinctRootEntityResultTransformer())
.List<Category>()
.Where(x => x.ParentCategory == null);
The main difference between this version and what you tried is how the "ParentCategory == null" filter is applied. It has to be left out of the query that is sent to the database in order to retrieve the whole tree - but we still need the query to only return the root nodes of the tree, so we'll use linq to find those after the database query has completed.
I used Daniel's code as a bases for solving the problem. I also experimented with the equivalent HQL that I shared below. The HQL executed slightly faster, but I went with ICriteria since I could then choose between FetchModel.Join and FetchModel.Lazy.
session.CreateQuery( "from Category as c left join fetch c.SubCategories" )
.SetResultTransformer( new DistinctRootEntityResultTransformer() )
.List<Category>()
.Where( c => c.ParentCategory == null );
Not sure if it helps but take a look at : map a tree in NHibernate
If I have a mapping like this:
<class name="Library" table="Libraries">
...
<dynamic-component name="Annotations">
<property name="LibraryResolver.AlgorithmVersion" column="`LibraryResolver.AlgorithmVersion`" type="Int32" />
</dynamic-component>
</class>
How should I write HQL or Linq-to-NHibernate query for all libraries where LibraryResolver.AlgorithmVersion is greater than a given value?
The HQL query below maybe along the lines you are looking for
from Library as lib
where lib.Annotations.LibraryResolver.AlgorithmVersion > 2
If you're using nhibernate, have you tried out the NHibernate LambdaExtensions? This library provides a set of extensions methods over the Criteria and DetachedCriteria apis which removes the need of magic strings when querying using the above two api.
Below is an example of how one might use NHibernate Detached Criteria query with the mentioned LambdaExtensions library
Answer answerAlias = null;
var actual = DetachedCriteria.For<Survey>()
.Add<Survey>( s => s.Status == SurveyStatus.Complete )
.Add<Questionnaire>( q => q.Id == questionnaireId )
.CreateAlias<Survey>( s => s.Answers, () => answerAlias )
.SetProjection( LambdaProjection.Property( () => answerAlias.Id ) );
I don't know whether this helps but when I use the Criteria API (in Java) it just works. Haven't tried with HQL though.
<dynamic-component name="values">
<property name="dynamicNameValue" column="ATTRIBUTE_1" type="string"/>
<property name="dynamicNumber" column="ATTRIBUTE_4" type="integer"/>
</dynamic-component>
Criteria criteria = session.createCriteria(DynamicAttributes.class)
.add(Expression.eq("values.dynamicNumber", 2));
Just some thought: could it be that the problem is that the name ('LibraryResolver.AlgorithmVersion') you're passing contains a dot? Maybe post some code you already attempted?
Let's say my domain looks like this:
I have an object, Vehicle, that has an OdometerReading property.
An OdometerReading has the Miles & Date (when it was read).
I need to keep a history of all OdometerReadings for the Vehicle in the database, but don't want the entire odometer history to belong to the Vehicle object. What I would like is for the OdometerReading property map to the most recent OdometerReading entry out of the database.
I thought about mapping the whole collection of OdometerReadings to the Vehicle, and having a dynamic property called CurrentOdometerReading that would order them and return the latest one, but I don't need the whole collection under the Vehicle in my domain, and it seems like I would be getting more data out of the database than I need.
Is that possible with NHibernate? How would I map such a thing?
There are a few ways of doing this depending on what you want your domain model to look like. My preferred choice is to use a custom collection type, for example IOdometerReadingCollection, which you can add extra methods to. In this case it might be something like:
public interface IOdometerReadingCollection : IList<OdometerReading>
{
OdometerReading Latest { get; }
}
This way you can do:
OdometerReading reading = vehicle.OdometerReadings.Latest;
which I prefer to:
OdometerReading reading = vehicle.LatestOdometerReading;
There's lots of documentation about custom collections, which you can find with a simple google search.
If this approach isn't for you there are other options. You may be able to use a property with a formula (I'm not sure if that works with complex types?), or a regular NHibernate association where you'd have the key of the latest OdometerReading on your Vehicle mapping. As you also mentioned you could just load all the OdometerReadings, which depending on your use case might actually be fine.
I hope this helps, or at least points you in the right direction.
There is a "where" clause that you can put in your collection mapping. Check the reference documentation.
I would map the OdometerReading property as a component, then use a named query to ensure it's populated with the latest reading out of the database. (In this example, you'd have a sql-query with a name of "vehicle" that does the SQL to load the Vehicle columns along with the latest Odometer reading)
<class name="Vehicle">
<property name="Type" not-null="true"/>
<component name="OdometerReading">
<property name="Miles" />
<property name="Date" />
</component>
<loader query-ref="vehicle"/>
</class>