I finished following the summer of nhibernate screen casts and am trying to convert it to fluent, just for the sake of knowledge.
I have two classes (very simple)
public class Customer { ... }
public class PreferredCustomer : Customer { ... }
These follow table per sub class strategy and so the fluent mapping is so:
CustomerMap -
//nothing related to PreferredCustomer - the spec says not required
public class PreferredCustomerMap : SubclassMap<PreferredCustomer>
{
Map(x => x.CustomerSince);
Map(x => x.OrderDiscountRate);
}
Thats it.
My test is failing, upon inspection, its complaining that sql cant find column customer_id
this is the sql produced by hibernate:
SELECT customer0_.CustomerId as CustomerId1_0_,
customer0_.Version as Version1_0_,
customer0_.Firstname as Firstname1_0_,
customer0_.Lastname as Lastname1_0_,
customer0_1_.CustomerSince as Customer2_2_0_,
customer0_1_.OrderDiscountRate as OrderDis3_2_0_,
//here, customer0_1_.customer_id needs to be CustomerID really.
case when customer0_1_.Customer_id is not null then 1 when customer0_.CustomerId is not null then 0 end as clazz_0_
FROM [Customer] customer0_ left outer join [PreferredCustomer] customer0_1_ on customer0_.CustomerId=customer0_1_.Customerid
WHERE customer0_.Customer_Id=1
Its clearly doing that only on PreferredCustomer joined table. Cant find what needs to be done.
Any Ideas please?
edit: how do I read the xml's produced by fluent? that could be a good start.
You need a call to KeyColumn("CustomerID"); in your SubclassMaps.
Related
Having a seemingly bizzare N+1 select problem in NHibernate. I am executing a query where I'm asking for a bunch of entities where one of its linked properties is null. I don't actually need the linked property to be returned in this case by NHibernate as its only for the purpose of selecting the right data.
First Entity is a booking Window
public class BookingWindow : Entity<BookingWindow>
{
// Blah blah blah
/// <summary>
/// Gets or sets the booking order item.
/// </summary>
/// <value>
/// The booking order item.
/// </value>
public virtual BookingWindowOrderItem BookingOrderItem { get; set; }
}
And the BookingWindowOrderItem as follows
public class BookingWindowOrderItem : OrderItem
{
// Blah blah blah
public virtual BookingWindow BookingWindow { get; set; }
}
Here are the respective mappings
public BookingWindowMap()
{
this.Schema("Customer");
this.Table("BookingWindows");
this.Id(x => x.Id).GeneratedBy.Guid();
this.Component(x => x.WindowPeriod, m =>
{
m.Map(x => x.Min, "StartTime");
m.Map(x => x.Max, "EndTime");
});
this.References(window => window.BookingOrderItem).PropertyRef("BookingWindow").Column("Id").LazyLoad().Nullable().ReadOnly();
this.Map(x => x.Price);
this.References(x => x.CustomerRoom).ForeignKey("RoomId").Column("RoomId");
}
And
public BookingWindowOrderItemMap()
{
this.DiscriminatorValue(1);
this.References(x => x.BookingWindow).LazyLoad().Column("OrderItemForeignId").ForeignKey("OrderItemForeignId");
}
Now When I execute the following query I get back the correct Booking windows that don't have an order item.
Session.QueryOver<BookingWindow>().Where(w => w.CustomerRoom.Id == Guid.Parse(roomId)).Left.JoinQueryOver(bw => bw.BookingOrderItem).WhereRestrictionOn(item => item.Id).IsNull.List<BookingWindow>();
So the first query gets issued to the database like so (the order item columns are selected which is a bit annoying but the real problem comes in a minute)
SELECT this_.Id as Id2_1_, this_.Price as Price2_1_, this_.RoomId as RoomId2_1_, this_.StartTime as StartTime2_1_, this_.EndTime as EndTime2_1_, bookingwin1_.Id as Id4_0_, bookingwin1_.Price as Price4_0_, bookingwin1_.Description as Descript4_4_0_, bookingwin1_.OrderId as OrderId4_0_, bookingwin1_.OrderItemParentId as OrderIte6_4_0_, bookingwin1_.OrderItemForeignId as OrderIte7_4_0_ FROM Customer.BookingWindows this_ left outer join Payment.OrderItem bookingwin1_ on this_.Id=bookingwin1_.OrderItemForeignId and bookingwin1_.OrderItemTypeId='1' WHERE this_.RoomId = ? and bookingwin1_.Id is null
But then for each booking window returned there is an extra select for the linked order item even though I haven't asked for it or need it. This happens within the query over method so I'm not doing any kind of iterating over the returned booking windows manually.
SELECT bookingwin0_.Id as Id4_0_, bookingwin0_.Price as Price4_0_, bookingwin0_.Description as Descript4_4_0_, bookingwin0_.OrderId as OrderId4_0_, bookingwin0_.OrderItemParentId as OrderIte6_4_0_, bookingwin0_.OrderItemForeignId as OrderIte7_4_0_ FROM Payment.OrderItem bookingwin0_ WHERE bookingwin0_.OrderItemForeignId=? and bookingwin0_.OrderItemTypeId='1'
Can anyone explain to me the error I have made here. Maybe its obvious but I've struggled for a few hours and at the end of my patience :)
I see one weird part in your mapping: Using References as a one-to-one mapping style. Maybe it is intended, but this is causing that issue you have.
Firstly, as documentation says [References / many-to-one][1]
References is for creating many-to-one relationships between two
entities, and is applied on the "many side." You're referencing a
single other entity, so you use the References method. #HasMany /
one-to-many is the "other side" of the References relationship, and
gets applied on the "one side."
Other words, in the table of the BookingWindowOrderItemMap you store reference to BookingWindow. It could mean (by the DB Design), that there could be more records of OrderItem, referencing the same BookingWindow. But maybe this is what you want, and you check "uniqueness" elsewhere. The more I tried to understand your problem, I would vote for moving the reference to OrderItem in a column in the BookingWindow
Problem revealed:
To your issue. When NHibernate recieves the list of BookingWindow, the next step is to build a proxy. In this process, all valueType/string properties are set, and for references... And for references NHibernate tries to prepare the lazy load.
Simplified version is, that into each property BookingWindowOrderItem BookingOrderItem is injected a promise for an instance of the BookingWindowOrderItem, to be returned when firstly touched. In standard cases, when mapping References is used, NHibernate in this moment already loaded from the table of the BookingWindow the ReferenceId.
In your case, this ReferenceID is represented by virtual, readonly 'current item ID'. The ID which definetly exists... but the reference does not! We've selected only BookingWindows which has NULL instead of the reference.
But we do have NOT NULL Reference ID (representd by Current instance ID).
And we've used .Left.JoinQueryOver. So NHibernate is sure, that it already loaded all data in the first query... but is confused, because in his session is no OrderItem with the id equal to BookingWindow.ID/ReferenceId
That's the reason (why it tries to fix it... and does load it again)
So this is the answer, why NHibernate does "weird selects". Not a suggestion how to fix it ;) it could be another question and answer...
I am trying to get fluent 1.2 to work on a project that currently uses v1.1. However the existing join code no longer works. I specify a Join in the map but it never appears in the SQL.
I have a class hierarchy mapped which includes a join (see below). The application uses some legacy tables that cannot be changed. Alternatively I could rewrite the code so that the joined properties can be mapped with a reference. However this is not really valid as it produces a domain object that does not exist.
public class IndividualMap : SubclassMap<Individual>
{
public IndividualMap()
{
Map(x => x.Title);
.....
Join("UserDefFields", x =>
{
x.KeyColumn("id");
x.Map(y => y.MembershipEnquirySource, "Anl9");
....
}
);
I have a simple model class (Part), which pulls from it's information from a single table (t_Part).
I would like a subclass of this model called (ProducedPart), that would still utilize NHibernate's caching mechanisms, but would only be instances of (Part) that have a foreign key relationship in a table called "t_PartProduction". I do not need to have a model for this second table.
I only need a read-only version of ProducedPart
I could always implement a Facade/Repository over this, but I was hoping to setup a mapping that would pull "t_Part" joined with "PartProduction" when I asked for "ProducedPart" in NH.
Is this the wrong way to use NH?
Edit
So, the SQL would look something like
SELECT p.*
FROM t_Part p
INNER JOIN t_PartProduction pp ON pp.PartID = p.PartID
WHERE pp.ProductionYear = '2009'
I believe what you are looking for is a joined subclass. In FNH, it will look something like:
public class PartMap : ClassMap<Part>
{
public PartMap()
{
Id(x => x.Id)
JoinedSubClass<ProducedPart>("PartID", sub => {
sub.Map(x => x.Name);
sub.Map(x => x.ProductionYear);
});
}
}
In order have NHibernate cache the results, you will need to have the subclass mapped (and if you didn't map it, you wouldn't be able to get NH to load it in the first place).
Bringing in some context from the FNH groups thread, it will not explicitly be read-only though. In my opinion, making things read-only is not an appropriate thing for NHibernate to manage. This is better controlled by the database and connections (i.e. creating a connection to the database that only has SELECT permissions on the tables/views being accessed). See my answer to a previous SO question about readonly sessions in NHibernate for more of my thoughts on the matter.
The key here is using both the where and mutable elements of the class definition for NHibernate Mappings.
Using Fluent NHibernate, this looks like:
public Part()
{
WithTable("t_Part");
Id(i => i.Id).ColumnName("PartID");
Map(m => m.Name).ColumnName("Part");
SetAttribute("where", "PartID IN ( SELECT pp.PartID FROM t_PartProduction pp WHERE pp.ProductionYear = '2009' ) ");
ReadOnly();
}
No, this is perfectly possible. Look in the NHibernate documentation for the "table per subclass" model of inheritance. It will actually implement this as a LEFT JOIN, so that when you load a Part, it creates an instance of either your Part or your ProducedPart class depending on whether the other row is present. You'll find documentation on nhibernate.info.
I'm not sure you could make ProducedPart read-only doing this though.
I'm assuming from this:
WHERE pp.ProductionYear = '2009'
that you want the subclass only where the production year is 2009, i.e. if when there is a record in t_PartProduction for a different year, you want this Part treated as a plain Part object, not a ProducedPart, then you could consider creating a view definition within your database that is a filtered version of t_PartProduction, then making your subclass join to this view rather than the base table.
I am using: NHibernate, NHibernate.Linq and Fluent NHibernate on SQL Server Express 2008. I am selecting an entity using a predicate on a referenced property (many-one mapping). I have fetch=join, unique=true, lazy-load=false. I enabled the log4net log and when any such query executes it logs two identical SQL queries. Running the query returns one row, and when I attempt to use the IQueryable.Single extension method it throws the exception stating there is more than one row returned. I also tried running the query using the standard IQuery.UniqueResult method with the same result, it ends up logging and actually running the query twice, then throwing an exception stating that there were multiple rows, however running the actual query in management studio returns only one result. When I disable logging I receive the same error.
The entities and mappings are declared as follows (proper access modifiers and member type variance are implied)
class User
{
int ID;
string UserName;
}
class Client
{
int ID;
User User;
Person Person;
Address Address;
}
class UserMap : ClassMap<User>
{
public UserMap()
{
Id(x => x.ID);
Map(x => x.UserName);
}
}
class ClientMap : ClassMap<Client>
{
public ClientMap()
{
Id(x => x.ID);
References(x => x.User).Unique();
...
}
}
Then I invoke a queries such as the following:
ISession s = GetNHibernateSession();
...
var client = s.Linq<Client>().SingleOrDefault(x => x.User.ID = 17);
or
var client = s.Linq<Client>().Where(x => x.User.ID = 17);
or
var client = s.CreateQuery("from Client as c where c.User.ID = 17").UniqueResult<Client>();
In all cases executes two identical queries. When I enable lazy load, the client is again loaded using two queries, however upon accessing a member, such as Person, only one additional query is executed.
Is this possibly a result of Fluent generating an improper mapping? Or SQL Server Express edition not being used properly by NHibernate?
The problem was caused by another mapping I had declared. I had a class inheriting from Client which had an associated mapping. This is what caused NHibernate to query twice. I noticed this because when using Linq() it returned the subclass, not Client itself. This particular instance of inheritance and mapping was a design flaw on my part and was the root of the whole problem!
NHibernate doesn't have any trouble with SQL Express, I've used it fairly extensively. Similarily, it's unlikely Fluent NHibernate is generating invalid mappings in this simple scenario (but not unheard of).
A shot in the dark, but I believe NHibernate reserves the name Id as an identifier name, so when it sees Id in the query it knows to just look at the foreign key instead of the actual joined entity. Perhaps your naming of ID instead of Id is throwing it off?
You could try using the excellent NHibernate profiler for a more detailed view of what is happening. It comes with a 30 day trial license and while in Beta there is a discount on the full license cost
Whenever I load a Task class, the Document property is always null, despite there being data in the db.
Task class:
public class Task
{
public virtual Document Document { get; set; }
Task Mapping override for AutoPersistenceModel:
public void Override(AutoMap<Task> mapping)
{
mapping.HasOne(x => x.Document)
.WithForeignKey("Task_Id");
As you can see form what NHProf says is being run, the join condition is wrong, the WithForeignKey doesnt seem to take effect. In fact, i can write any string in the above code and it makes no difference.
FROM [Task] this_
left outer join [Document] document2_
on this_.Id = document2_.Id
It should be:
FROM [Task] this_
left outer join [Document] document2_
on this_.Id = document2_.Task_Id
If i hack the data in the db so that the ids match, then data is loaded, but obviously this is incorrect - but at least it proves it loads data.
Edit: rummaging in the fluent nhib source to find the XML produces this:
<one-to-one foreign-key="Task_Id" cascade="all" name="Document" class="MyProject.Document, MyProject, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" />
Edit: heres the schema:
CREATE TABLE [dbo].[Document](
[Id] [int] IDENTITY(1,1) NOT NULL,
[Task_Id] [int] NOT NULL,
CREATE TABLE [dbo].[Task](
[Id] [int] IDENTITY(1,1) NOT NULL,
Anyone got any ideas?
Thanks
Andrew
I ran into the same issue today. I believe the trick is not to use .ForeignKey(...) with the .HasOne mapping, but to use .PropertyRef(...) instead. The following is how I define a One-to-one relationship between an Organisation (Parent) and its Admin (Child):
HasOne(x => x.Admin).PropertyRef(r => r.Organisation).Cascade.All();
The Admin has a simple reference to the Organisation using its Foreign Key:
References(x => x.Organisation, "ORAD_FK_ORGANISATION").Not.Nullable();
When retrieving an Organisation, this will load up the correct Admin record, and properly cascades updates and deletes.
You should use:
References(x => x.Document, "DocumentIdColumnOnTask")
I think the problem here is that the "HasOne" convention means that you are pointing at the other thing(the standard relational way to say "Many To One"/"One to One"); By putting a Task_ID on the document the actual relationship is a HasMany but you have some kind of implicit understanding that there will only be one document per task.
Sorry - I don't know how to fix this, but I will be interested in seeing what the solution is (I don't use NHibernate or Fluent NHibernate, but I have been researching it to use in the future). A solution (from someone with very little idea) would be to make Documents a collection on Task, and then provide a Document property that returns the first one in the collection (using an interface that hides the Documents property so no one thinks they can add new items to it).
Looking through documentation and considering eulerfx's answer, Perhaps the approach would be something like:
References(x => x.Document)
.TheColumnNameIs("ID")
.PropertyRef(d => d.Task_ID);
EDIT: Just so this answer has the appropriate solution: The correct path is to update the database schema to match the intent of the code. That means adding a DocumentID to the Task table, so there is a Many-To-One relationship between Task and Document. If schema changes were not possible, References() would be the appropriate resolution.
I've tried this solution:
just in Document:
mapping.HasOne(x => x.Task).ForeignKey("Task_ID").Constrained().Cascade.All();
As eulerfx pointed out,
the table structure indicates that there maybe mulitple documents for a task
and Chris stated:
By putting a Task_ID on the document the actual relationship is a HasMany but you have some kind of implicit understanding that there will only be one document per task.
This is of course correct so I have reversed it so Task has a nullable Document_Id.
Thanks to both of you for you help!
I flipped a coin for the accepted answer, if i could tick both i would!
I have been struggling with the same Has One problem and finally found that this worked:
public class ParentMap : ClassMap<Parent>
{
public ParentMap()
{
Id(x => x.Id);
HasOne(s => s.Child).Cascade.All();
}
}
public class ChildMap : ClassMap<Model.Child>
{
public ChildMap()
{
Id(x => x.Id);
HasOne(s => s.Parent).Constrained().ForeignKey();
}
}