I have a legacy system where the relationship between 2 tables haven't been defined explictly and there aren't any keys (primary or unqiue defined). The only related columns is 'Username'
Something like:
Table: Customer
Column: Id,
Column: Username,
Column: FirstName,
Table: Customer_NEW
Column: Username
Column: FirstNameNew
I have following Mapping definitions:
public sealed class CustomerMap : ClassMap<Customer>, IMap
{
public CustomerMap()
{
WithTable("customers");
Not.LazyLoad();
Id(x => x.Id).GeneratedBy.Increment();
References(x => x.CustomerNew, "Username")
.WithForeignKey("Username")
.Cascade.All();
}
public sealed class CustomerNewMap : ClassMap<CustomerNew>, IMap
{
public CustomerNewMap()
{
WithTable("customers_NEW");
Not.LazyLoad();
Id(x => x.Username).GeneratedBy.Assigned();
Map(x => x.FirstNameNew);
}
}
The problem is nHibernate is generating an UPDATE statement for the 'Reference' in the Customer Mapping definition which is obviously failing when attempting to insert a new Customer object which has a reference to CustomerNew object.
How do I get the mapping definition to generate the INSERT statement instead of an UPDATE for the 'Save' command?
Cheers in advance
Ollie
The reason is because there isn't any referential integrity in the database, no primary keys, composite keys not foreign key constraints…
Yet again another application that has a database that’s not fit for purpose…
Related
I have a very simple unidirectional mappings. see below:
public ContactMap()
{
Id(x => x.Id).GeneratedBy.Assigned();
Map(x => x.Name);
References(x => x.Device);
HasMany(x => x.Numbers)
.Not.Inverse()
.Not.KeyNullable()
.Cascade.AllDeleteOrphan()
.Not.LazyLoad()
.Fetch.Subselect();
Table("Contacts");
}
public PhoneNumberMap()
{
Id(x => x.Id).GeneratedBy.Native();
Map(x => x.Number);
Table("ContactNumbers");
}
According to this post after nhibernate 3 and above, setting key as non-nullable should fix the insert-update issue (The issue when NHibernate issues an insert with foreign key set to null and then an update to update the foreign key to correct value), but this is not the case for me. When I set the key as not nullable, NHibernate issues a correct insert statement
INSERT INTO ContactNumbers
(Number,
ContactId)
VALUES ('(212) 121-212' /* #p0 */,
10 /* #p1 */);
As you can see, it inserts ContactId field, but after that, it still issues update statement
UPDATE ContactNumbers
SET ContactId = 10 /* #p0 */
WHERE Id = 34 /* #p1 */
So to clarify the problem. NHibernate inserts Contact row with foreign key assigned correctly and after that, it issues an update statement to update the foreign key (ContactId) which is redundant.
How can I get rid of this redundant update statement?
Thanks.
BTW, I'm using latest version of NHibernate and Fluent NHibernate. The database is SQLite
You have to set "updatable"=false to your key to prevent update.
public ContactMap()
{
Id(x => x.Id).GeneratedBy.Assigned();
Map(x => x.Name);
References(x => x.Device);
HasMany(x => x.Numbers)
.Not.Inverse()
.Not.KeyNullable()
.Not.KeyUpdate() // HERE IT IS
.Cascade.AllDeleteOrphan()
.Not.LazyLoad()
.Fetch.Subselect();
Table("Contacts");
}
You can't as of 3.2.0 BETA.
In v3.2.0 BETA an improvment to one-to-many introduced this anomaly to uni-directional one-to-many relationships (actually I am not sure if anormaly is what you would call this).
Before 3.2 you would need to set the foreign key to allow nulls for this type of relationship to work. So I would ignore the fact that this happens and just go with it. Otherwise you will need to change it to a fully bi-directional relationship.
[NH-941] - One-Many Requiring Nullable Foreign Keys
Release notes or JIRA issue
edit Also the answer to the post you point to is to fix save null-save-update rather than fixing the addtional update
Try setting inverse to true on the mapping and assigning the relationship in code.
Inverse means that the child is responsible for holding the ID of the parent.
e.g.
var contact = new Contact();
var phoneNumber = new PhoneNumber();
phoneNumber.Contact = contact;
That way, when you do the insert for the PhoneNumber record, NH can insert the ContactId without having to do a separate update.
That's what I used to do in NH 2, I would assume the behaviour still works the same in 3.
I don't know if you really can get rid of it.
Try using another id generator as native. It forces NH to insert the record only to get the id. The id is used for every entity in the session, so it can't do the insert later. It may case subsequent updates. Use hi-lo or something similar.
Edit
Why aren't you using a component in this case? You don't need to map the phone number separately, if they consist only of a number. Something like this (I'm not a FNH user, so it may be wrong):
public ContactMap()
{
Id(x => x.Id).GeneratedBy.Assigned();
Map(x => x.Name);
References(x => x.Device);
HasMany(x => x.Numbers)
.Not.Inverse()
.Not.KeyNullable()
.Cascade.AllDeleteOrphan()
.Not.LazyLoad()
.Fetch.Subselect()
.Component(c =>
{
Map(x => x.Number);
})
.Table("ContactNumbers");
Table("Contacts");
}
It is what Trevor Pilley said. Use inverse="true". If you choose not to have inverse="true", this is the consequence of that choice. You can't have it both ways.
I currently have the following relationship: ProductUom -> ProductImage
They both have the same primary keys: PROD_ID and UOM_TYPE
I have them mapped like this:
public ProductUomMap()
{
Table("PROD_UOM");
CompositeId()
.KeyReference(x => x.Product, "PROD_ID")
.KeyProperty(x => x.UomType, "UOM_TYPE");
References(x => x.Image)
.Columns(new string[] { "PROD_ID", "UOM_TYPE" })
.Not.Update()
.Not.Insert()
.NotFound.Ignore()
.Cascade.All();
}
public ProductImageMap()
{
Table("PROD_UOM_IMAGE");
CompositeId()
.KeyReference(x => x.ProductUom, new string[] {"PROD_ID", "UOM_TYPE"});
Map(x => x.Image, "PROD_IMAGE").Length(2147483647);
}
Whenever I create a ProductUom object that has a ProductImage it tries to insert the ProductImage first which results in a foreign key violation. I swear this was working at one time with the mapping that I have but it doesn't now.
I need the ProductImage to be a Reference (many-to-one) because the relationship here is optional and I want to be able to lazy load product images. The inserts do work correctly if I use a HasOne (one-to-one) mapping but the I cannot lazy load when I do this and querying a ProductUom seems to cause issues.
Is there something that I'm missing here? How can this mapping be modified to get what I want?
can you use LazyLoaded Properties? Then you could use something like this
Join("PROD_UOM_IMAGE", join =>
{
join.KeyColumn("PROD_ID", "UOM_TYPE");
join.Optional();
join.Map(x => x.Image, "PROD_IMAGE").Length(2147483647).LazyLoad();
}
another option is:
Id().GeneratedBy.Foreign(x => x.ProductUom);
can't test it here though, i'm writing on Mobile
I have a parent-child relationship that I've put a test case together between Users and Groups. I did this to replicate a failure in
a Parent-Child relationship when trying to perform a cacade insert using thes relationship.
The two SQL tables are as follows:
CREATE TABLE [dbo].[User]
(
[Id] [int] IDENTITY(1,1) NOT NULL PRIMARY KEY,
[Name] [varchar](50) NOT NULL,
)
CREATE TABLE [dbo].[Group]
(
[Id] [int] IDENTITY(1,1) NOT NULL PRIMARY KEY,
[GroupName] [varchar](50) NOT NULL,
[UserId] [int] NOT NULL,
)
ALTER TABLE [dbo].[Group] WITH CHECK ADD CONSTRAINT [FK_Group_User] FOREIGN KEY([UserId])
REFERENCES [dbo].[User] ([Id])
The objects represent these two tables with the following mappings:
public class UserMap : ClassMap<User>
{
public UserMap()
{
Table("[User]");
Id(x => x.Id).GeneratedBy.Identity();
Map(x => x.Name).Not.Nullable();
HasMany(x => x.Groups).KeyColumn("UserId").Cascade.SaveUpdate();
}
}
public class GroupMap : ClassMap<Group>
{
public GroupMap()
{
Table("[Group]");
Id(x => x.Id).GeneratedBy.Identity();
Map(x => x.GroupName).Not.Nullable();
References(x => x.User).Column("UserId").Not.Nullable();
}
}
The code to created the objects is simply:
User u = new User() { Name = "test" };
Group g = new Group() { GroupName = "Test Group" };
u.Groups.Add(g);
using (var session = factory.OpenSession())
{
session.SaveOrUpdate(u);
}
However it fails with exception "Cannot insert the value NULL into column 'UserId', table 'test.dbo.Group'; column does not allow nulls. INSERT fails.
The statement has been terminated". I suspect that this is dude to the parent object's Id (an identity column) being passed through as NULL and not the new values. Is this a bug or is there a way to fix these mappings so that this cascade relationship succeeds?
I recently had this exact type of mapping working fine in a project. My advice is:
Learn how the Inverse attribute of a HasMany relationship works. Great explanation here
You need a two way association between the parent and child object. This is explained at the bottom of the article linked to above.
Another good advice is to encapsulate your collections better
- Don't access your collections modification methods directly. The collection properties should be read-only and the parent (User class in your case) should have AddGroup() and RemoveGroup() methods that changes the private collection. In order for this to work you have to let NHibernate access the private collection member by using the .Access.CamelCaseField(Prefix.Underscore) or similar mapping attribute. Good discussion about it here
I can post an example mapping and class files if needed.
You will have to save the user first then assign the group to the user and save that:
using (var session = factory.OpenSession())
{
User u = new User() { Name = "test"};
session.SaveOrUpdate(u);
Group g = new Group() { GroupName = "Test Group", User = u };
session.SaveOrUpdate(g)
}
I have found that you cannot cascade save child /parent related objects which have only just been created.
So, I'm having a problem mapping in fluent nhibernate. I want to use a join mapping to flatten an intermediate table: Here's my structure:
[Vehicle]
VehicleId
...
[DTVehicleValueRange]
VehicleId
DTVehicleValueRangeId
AverageValue
...
[DTValueRange]
DTVehicleValueRangeId
RangeMin
RangeMax
RangeValue
Note that DTValueRange does not have a VehicleID. I want to flatten DTVehicleValueRange into my Vehicle class. Tgis works fine for AverageValue, since it's just a plain value, but I can't seem to get a ValueRange collection to map correctly.
public VehicleMap()
{
Id(x => x.Id, "VehicleId");
Join("DTVehicleValueRange", x =>
{
x.Optional();
x.KeyColumn("VehicleId");
x.Map(y => y.AverageValue).ReadOnly();
x.HasMany(y => y.ValueRanges).KeyColumn("DTVehicleValueRangeId"); // This Guy
});
}
The HasMany mapping doesn't seem to do anything if it's inside the Join. If it's outside the Join and I specify the table, it maps, but nhibernate tries to use the VehicleID, not the DTVehicleValueRangeId.
What am I doing wrong?
Can you explain the average value column in the DTVehicleValueRange table? Isn't this a calculated value (i.e. no need to persist it)?
It looks like you have a many-to-many relationship between Vehicle and DTValueRange, which of course would not be mapped with a join, rather with a HasManyToMany call.
Ran into a similar issue today using a Map to create a view. The SQL generated showed it trying to do the HasMany<> inside the join based on the Id of the ParentThing and not WorkThing (same problem you were having)
After much mapping of head-to-desk it turns out adding the propertyref onto the hasmany solved it.
public class ThingMap : ClassMap<WorkThingView> {
public ThingMap() {
ReadOnly();
Table("ParentThing");
Id(x => x.ParentThingId);
Map(x => x.ParentName);
Join("WorkThing", join => {
join.KeyColumn("ParentThingId");
join.Map(m => m.FooCode);
join.Map(m => m.BarCode);
join.Map(x => x.WorkThingId);
join.HasMany(x => x.WorkThingCodes)
.Table("WorkThingCode").KeyColumn("WorkThingId").PropertyRef("WorkThingId")
.Element("WorkThingCode");
});
}
}
Entities:
Team <-> TeamEmployee <-> Employee
Requirements:
A Team and an Employee can exist without its counterpart.
In the Team-TeamEmployee relation the Team is responsible (parent) [using later a TeamRepository].
In the Employee-TeamEmployee relation the Employee is responsible (parent) [using later an EmployeeRepository].
Duplicates are not allowed.
Deleting a Team deletes all Employees in the Team, if the Employee is not in another Team.
Deleting an Employee deletes only a Team, if the Team does not contain no more Employees.
Mapping:
public class TeamMap : ClassMap<Team>
{
public TeamMap()
{
// identity mapping
Id(p => p.Id)
.Column("TeamID")
.GeneratedBy.Identity();
// column mapping
Map(p => p.Name);
// associations
HasMany(p => p.TeamEmployees)
.KeyColumn("TeamID")
.Inverse()
.Cascade.SaveUpdate()
.AsSet()
.LazyLoad();
}
}
public class EmployeeMap : ClassMap<Employee>
{
public EmployeeMap()
{
// identifier mapping
Id(p => p.Id)
.Column("EmployeeID")
.GeneratedBy.Identity();
// column mapping
Map(p => p.EMail);
Map(p => p.LastName);
Map(p => p.FirstName);
// associations
HasMany(p => p.TeamEmployees)
.Inverse()
.Cascade.SaveUpdate()
.KeyColumn("EmployeeID")
.AsSet()
.LazyLoad();
HasMany(p => p.LoanedItems)
.Cascade.SaveUpdate()
.LazyLoad()
.KeyColumn("EmployeeID");
}
}
public class TeamEmployeeMap : ClassMap<TeamEmployee>
{
public TeamEmployeeMap()
{
Id(p => p.Id);
References(p => p.Employee)
.Column("EmployeeID")
.LazyLoad();
References(p => p.Team)
.Column("TeamID")
.LazyLoad();
}
}
Creating Employees and Teams:
var employee1 = new Employee { EMail = "Mail", FirstName = "Firstname", LastName = "Lastname" };
var team1 = new Team { Name = "Team1" };
var team2 = new Team { Name = "Team2" };
employee1.AddTeam(team1);
employee1.AddTeam(team2);
var employee2 = new Employee { EMail = "Mail2", FirstName = "Firstname2", LastName = "Lastname2" };
var team3 = new Team { Name = "Team3" };
employee2.AddTeam(team3);
employee2.AddTeam(team1);
team1.AddEmployee(employee1);
team1.AddEmployee(employee2);
team2.AddEmployee(employee1);
team3.AddEmployee(employee2);
session.SaveOrUpdate(team1);
session.SaveOrUpdate(team2);
session.SaveOrUpdate(team3);
session.SaveOrUpdate(employee1);
session.SaveOrUpdate(employee2);
After this I commit the changes by using transaction.Commit().
The first strange thing is that I have to save Teams and Employees instead only one of them (why?!). If I only save all teams or (Xor) all employees then I get a TransientObjectException:
"object references an unsaved
transient instance - save the
transient instance before flushing.
Type: Core.Domain.Model.Employee,
Entity: Core.Domain.Model.Employee"
When I save all created Teams and Employees everything saves fine, BUT the relation table TeamEmployee has duplicate assoications.
ID EID TID
1 1 1
2 2 1
3 1 2
4 2 3
5 1 1
6 1 2
7 2 3
8 2 1
So instead of 4 relations there are 8 relations. 4 relations for the left side and 4 relations for the right side. :[
What do I wrong?
Further questions: When I delete a Team or an Employee, do I have to remove the team or the Employee from the TeamEmployee list in the object model or does NHibernate make the job for me (using session.delete(..))?
You are talking about business logic. It's not the purpose of NHibernate to implement the business logic.
What your code is doing:
You mapped two different collections of TeamEmployees, one in Team, one in Employee. In your code, you add items to both collections, creating new instances of TeamEmployee each time. So why do you expect that NHibernate should not store all these distinct instances?
What you could do to fix it:
You made TeamEmployee an entity (in contrast to a value type). To create an instance only once, you would have to instantiate it only once in memory and reuse it in both collections. Only do this when you really need this class in your domain model. (eg. because it contains additional information about the relations and is actually an entity of its own.)
If you don't need the class, it is much easier to map it as a many-to-many relation (as already proposed by Chris Conway). Because there are two collections in memory which are expected to contain the same data, you tell NHibernate to ignore one of them when storing, using Inverse.
The parent on both ends problem
There is no parent on both ends. I think it's clear that neither the Team nor the Employee is a parent of the other, they are independent. You probably mean that they are both parents of the intermediate TeamEmployee. They can't be parent (and therefore owner) of the same instance. Either one of them is the parent, or it is another independent instance, which makes managing it much more complicated (this is how you implemented it now). If you map it as a many-to-many relation, it will be managed by NHibernate.
To be done by your business logic:
storing new Teams and new Employees
managing the relations and keeping them in sync
deleting Teams and Employees when they are not used anymore. (There is explicitly no persistent garbage collection implementation in NHibernate, for several reasons.)
Looks like you need a HasManyToMany instead of two HasMany maps. Also, there is no need for the TeamEmployeeMap unless you have some other property in that table that needs mapped. Another thing, only one side needs to have the Inverse() set and since you're adding teams to employees I think you need to make the TeamMap the inverse. Having the inverse on one side only will get rid of the duplicate entries in the database.
Maybe something like this:
public class TeamMap : ClassMap<Team>
{
public TeamMap()
{
// identity mapping
Id(p => p.Id)
.Column("TeamID")
.GeneratedBy.Identity();
// column mapping
Map(p => p.Name);
// associations
HasManyToMany(x => x.TeamEmployees)
.Table("TeamEmployees")
.ParentKeyColumn("TeamID")
.ChildKeyColumn("EmployeeID")
.LazyLoad()
.Inverse()
.AsSet();
}
}
public class EmployeeMap : ClassMap<Employee>
{
public EmployeeMap()
{
// identifier mapping
Id(p => p.Id)
.Column("EmployeeID")
.GeneratedBy.Identity();
// column mapping
Map(p => p.EMail);
Map(p => p.LastName);
Map(p => p.FirstName);
// associations
HasManyToMany(x => x.TeamEmployees)
.Table("TeamEmployees")
.ParentKeyColumn("EmployeeID")
.ChildKeyColumn("TeamID")
.Cascade.SaveUpdate()
.LazyLoad()
.AsSet();
HasMany(p => p.LoanedItems)
.Cascade.SaveUpdate()
.LazyLoad()
.KeyColumn("EmployeeID");
}
}
Using this, the delete will delete the TeamEmployee from the database for you.
NHibernate does not allow many-to-many association with parents at both ends.