Brandon Wenzel Brandon Wenzel -4 years ago 135
C# Question

NHibernate Has-Many Collection With Cascading Deletes is Failing

Objective:

Create a parent-child relationship such that modifications to the parent's list of children will propagate to all of the children and have NHibernate do the heavy lifting.
The parent-child relationship will be a

Has-Many
on a self referencing table.

Problem:

Any attempt at deleting the parent (the root) object causes exceptions instead of the expected behavior of deleting the child objects.

Versions of stuff I am using:

Microsoft SQL Server Management Studio Version 10.0.4064.0

FluentNHibernate Version 1.3

NHibernate Version 3.2.0.4

Below is the set of current class objects and table structure I am using to replicate this behavior.




// Entity
class Task
{
ID { get; set; }
public virtual IList<Task> Children { get; set; }
public virtual byte[] Version { get; protected set; }
public virtual bool IsNew() { return ID <= 0; }

public Task()
{
this.Children = new System.Collections.Generic.List<Task>();
}
// Other properties excluded for brevity
}





// Map
class TaskMap : ClassMap<Task>
{
TaskMap()
{
Table("Task");

Id(x => x.ID, "ID")
.GeneratedBy.HiLo(
"NH_HiLo", "NextHigh", "100",
string.Format("TableName = '{0}'", "Task"));

HasMany<Task>(x => x.Children)
.KeyColumn("ParentTaskID")
.Cascade.AllDeleteOrphan();

// Other properties omitted for brevity

Version(x => x.Version)
.Not.Nullable()
.Generated.Always()
.Column("Version")
.CustomSqlType("timestamp");
}
}





// Repository Delete Method:
public virtual void Delete(Task value)
{
// CurrentSession is an ISession object that is currently open
using (var transaction = CurrentSession.BeginTransaction())
{
try
{
CurrentSession.Delete(value);
transaction.Commit();
}
catch (Exception)
{
transaction.Rollback();
throw;
}
}
}





// Test Case using NUnit.Framework and FluentNHibernate.Testing:
[TestFixtureSetUp]
public void SetUpFixture()
{
_repository = new Repository();
}

[Test]
public void MappingTest()
{
var task = new Task(); // Omitted assigning other properties for brevity

var entity = new Task(); // Omitted assigning other properties for brevity
entity.Children.Add(task);

_entity = new PersistenceSpecification<Task>(_repository.CurrentSession)
.VerifyTheMappings(entity);
}

[TearDown]
public void TearDown()
{
if (_entity != null && !_entity.IsNew())
{
_repository.Delete(_entity);
_entity = null;
}
}





--Table Script:
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE TABLE [dbo].[Task](
[ID] [bigint] NOT NULL,
[ParentTaskID] [bigint] NULL, -- Notice it DOES HAVE a NULLable FK reference.
[Version] [timestamp] NOT NULL,
CONSTRAINT [PK_MyTable] PRIMARY KEY CLUSTERED(
[ID] ASC
) WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF,
IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON,
ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]

GO
ALTER TABLE [dbo].[Task] WITH CHECK ADD CONSTRAINT [FK_TasksChild_TasksParent]
FOREIGN KEY([ParentTaskID])
REFERENCES [dbo].[Task] ([ID]) -- Notice the self table reference for child objects
GO
ALTER TABLE [dbo].[Task] CHECK CONSTRAINT [FK_TasksChild_TasksParent]
GO





With the above table and classes, changing the cascade to these options and executing the specified during the teardown of the test, these are the results.




With Cascade.AllDeleteOrphan:

Simply calling delete on the parent object I get this exception:

NHibernate.StaleObjectStateException was unhandled by user code
Message=Row was updated or deleted by another transaction (or unsaved-value mapping was incorrect): [Task#1015859]
Source=NHibernate
EntityName=Entities.Task
StackTrace:
at NHibernate.Persister.Entity.AbstractEntityPersister.Check(Int32 rows, Object id, Int32 tableNumber, IExpectation expectation, IDbCommand statement) in d:\CSharp\NH\NH\nhibernate\src\NHibernate\Persister\Entity\AbstractEntityPersister.cs:line 2178
at NHibernate.Persister.Entity.AbstractEntityPersister.Delete(Object id, Object version, Int32 j, Object obj, SqlCommandInfo sql, ISessionImplementor session, Object[] loadedState) in d:\CSharp\NH\NH\nhibernate\src\NHibernate\Persister\Entity\AbstractEntityPersister.cs:line 2912
at NHibernate.Persister.Entity.AbstractEntityPersister.Delete(Object id, Object version, Object obj, ISessionImplementor session) in d:\CSharp\NH\NH\nhibernate\src\NHibernate\Persister\Entity\AbstractEntityPersister.cs:line 3095
at NHibernate.Action.EntityDeleteAction.Execute() in d:\CSharp\NH\NH\nhibernate\src\NHibernate\Action\EntityDeleteAction.cs:line 70
at NHibernate.Engine.ActionQueue.Execute(IExecutable executable) in d:\CSharp\NH\NH\nhibernate\src\NHibernate\Engine\ActionQueue.cs:line 136
at NHibernate.Engine.ActionQueue.ExecuteActions(IList list) in d:\CSharp\NH\NH\nhibernate\src\NHibernate\Engine\ActionQueue.cs:line 126
at NHibernate.Engine.ActionQueue.ExecuteActions() in d:\CSharp\NH\NH\nhibernate\src\NHibernate\Engine\ActionQueue.cs:line 174
at NHibernate.Event.Default.AbstractFlushingEventListener.PerformExecutions(IEventSource session) in d:\CSharp\NH\NH\nhibernate\src\NHibernate\Event\Default\AbstractFlushingEventListener.cs:line 249
at NHibernate.Event.Default.DefaultFlushEventListener.OnFlush(FlushEvent event) in d:\CSharp\NH\NH\nhibernate\src\NHibernate\Event\Default\DefaultFlushEventListener.cs:line 19
at NHibernate.Impl.SessionImpl.Flush() in d:\CSharp\NH\NH\nhibernate\src\NHibernate\Impl\SessionImpl.cs:line 1489
at NHibernate.Transaction.AdoTransaction.Commit() in d:\CSharp\NH\NH\nhibernate\src\NHibernate\Transaction\AdoTransaction.cs:line 190
at Repositories.Repository.Delete(Task value) in ..\Repositories\Repository.cs:line 22
at TaskTest.TearDown() in ..\Tests\TaskTest.cs:line 76





After iterating through each of the children, recursively digging through those children's children and attempting to delete each child from the bottom up:

NHibernate.ObjectDeletedException was unhandled by user code
Message=deleted object would be re-saved by cascade (remove deleted object from associations)[Task#1016061]
Source=NHibernate
EntityName=Entities.Task
StackTrace:
at NHibernate.Impl.SessionImpl.ForceFlush(EntityEntry entityEntry) in d:\CSharp\NH\NH\nhibernate\src\NHibernate\Impl\SessionImpl.cs:line 914
at NHibernate.Event.Default.DefaultSaveOrUpdateEventListener.EntityIsTransient(SaveOrUpdateEvent event) in d:\CSharp\NH\NH\nhibernate\src\NHibernate\Event\Default\DefaultSaveOrUpdateEventListener.cs:line 140
at NHibernate.Event.Default.DefaultSaveOrUpdateEventListener.PerformSaveOrUpdate(SaveOrUpdateEvent event) in d:\CSharp\NH\NH\nhibernate\src\NHibernate\Event\Default\DefaultSaveOrUpdateEventListener.cs:line 76
at NHibernate.Event.Default.DefaultSaveOrUpdateEventListener.OnSaveOrUpdate(SaveOrUpdateEvent event) in d:\CSharp\NH\NH\nhibernate\src\NHibernate\Event\Default\DefaultSaveOrUpdateEventListener.cs:line 53
at NHibernate.Impl.SessionImpl.FireSaveOrUpdate(SaveOrUpdateEvent event) in d:\CSharp\NH\NH\nhibernate\src\NHibernate\Impl\SessionImpl.cs:line 2662
at NHibernate.Impl.SessionImpl.SaveOrUpdate(String entityName, Object obj) in d:\CSharp\NH\NH\nhibernate\src\NHibernate\Impl\SessionImpl.cs:line 549
at NHibernate.Engine.CascadingAction.SaveUpdateCascadingAction.Cascade(IEventSource session, Object child, String entityName, Object anything, Boolean isCascadeDeleteEnabled) in d:\CSharp\NH\NH\nhibernate\src\NHibernate\Engine\CascadingAction.cs:line 249
at NHibernate.Engine.Cascade.CascadeToOne(Object parent, Object child, IType type, CascadeStyle style, Object anything, Boolean isCascadeDeleteEnabled) in d:\CSharp\NH\NH\nhibernate\src\NHibernate\Engine\Cascade.cs:line 216
at NHibernate.Engine.Cascade.CascadeAssociation(Object parent, Object child, IType type, CascadeStyle style, Object anything, Boolean isCascadeDeleteEnabled) in d:\CSharp\NH\NH\nhibernate\src\NHibernate\Engine\Cascade.cs:line 181
at NHibernate.Engine.Cascade.CascadeProperty(Object parent, Object child, IType type, CascadeStyle style, Object anything, Boolean isCascadeDeleteEnabled) in d:\CSharp\NH\NH\nhibernate\src\NHibernate\Engine\Cascade.cs:line 148
at NHibernate.Engine.Cascade.CascadeCollectionElements(Object parent, Object child, CollectionType collectionType, CascadeStyle style, IType elemType, Object anything, Boolean isCascadeDeleteEnabled) in d:\CSharp\NH\NH\nhibernate\src\NHibernate\Engine\Cascade.cs:line 240
at NHibernate.Engine.Cascade.CascadeCollection(Object parent, Object child, CascadeStyle style, Object anything, CollectionType type) in d:\CSharp\NH\NH\nhibernate\src\NHibernate\Engine\Cascade.cs:line 201
at NHibernate.Engine.Cascade.CascadeAssociation(Object parent, Object child, IType type, CascadeStyle style, Object anything, Boolean isCascadeDeleteEnabled) in d:\CSharp\NH\NH\nhibernate\src\NHibernate\Engine\Cascade.cs:line 185
at NHibernate.Engine.Cascade.CascadeProperty(Object parent, Object child, IType type, CascadeStyle style, Object anything, Boolean isCascadeDeleteEnabled) in d:\CSharp\NH\NH\nhibernate\src\NHibernate\Engine\Cascade.cs:line 148
at NHibernate.Engine.Cascade.CascadeOn(IEntityPersister persister, Object parent, Object anything) in d:\CSharp\NH\NH\nhibernate\src\NHibernate\Engine\Cascade.cs:line 126
at NHibernate.Event.Default.AbstractFlushingEventListener.CascadeOnFlush(IEventSource session, IEntityPersister persister, Object key, Object anything) in d:\CSharp\NH\NH\nhibernate\src\NHibernate\Event\Default\AbstractFlushingEventListener.cs:line 207
at NHibernate.Event.Default.AbstractFlushingEventListener.PrepareEntityFlushes(IEventSource session) in d:\CSharp\NH\NH\nhibernate\src\NHibernate\Event\Default\AbstractFlushingEventListener.cs:line 197
at NHibernate.Event.Default.AbstractFlushingEventListener.FlushEverythingToExecutions(FlushEvent event) in d:\CSharp\NH\NH\nhibernate\src\NHibernate\Event\Default\AbstractFlushingEventListener.cs:line 48
at NHibernate.Event.Default.DefaultFlushEventListener.OnFlush(FlushEvent event) in d:\CSharp\NH\NH\nhibernate\src\NHibernate\Event\Default\DefaultFlushEventListener.cs:line 18
at NHibernate.Impl.SessionImpl.Flush() in d:\CSharp\NH\NH\nhibernate\src\NHibernate\Impl\SessionImpl.cs:line 1489
at NHibernate.Transaction.AdoTransaction.Commit() in d:\CSharp\NH\NH\nhibernate\src\NHibernate\Transaction\AdoTransaction.cs:line 190
at Repositories.Repository.Delete(Task value) in ..\Repositories\Repository.cs:line 22
at Repositories.Repository.Delete(Task value) in ..\Repositories\Repository.cs:line 25
at Repositories.Repository.Delete(Task value) in ..\Repositories\Repository.cs:line 25
at Tests.TaskTest.TearDown() in ..\Tests\TaskTest.cs:line 76





After iterating through the children, clearing each of their sets of children, then saving/deleting the parent I get this exception:

NHibernate.StaleObjectStateException was unhandled by user code
Message=Row was updated or deleted by another transaction (or unsaved-value mapping was incorrect): [Task#1015960]
Source=NHibernate
EntityName=Entities.Task
StackTrace:
at NHibernate.Persister.Entity.AbstractEntityPersister.Check(Int32 rows, Object id, Int32 tableNumber, IExpectation expectation, IDbCommand statement) in d:\CSharp\NH\NH\nhibernate\src\NHibernate\Persister\Entity\AbstractEntityPersister.cs:line 2178
at NHibernate.Persister.Entity.AbstractEntityPersister.Delete(Object id, Object version, Int32 j, Object obj, SqlCommandInfo sql, ISessionImplementor session, Object[] loadedState) in d:\CSharp\NH\NH\nhibernate\src\NHibernate\Persister\Entity\AbstractEntityPersister.cs:line 2912
at NHibernate.Persister.Entity.AbstractEntityPersister.Delete(Object id, Object version, Object obj, ISessionImplementor session) in d:\CSharp\NH\NH\nhibernate\src\NHibernate\Persister\Entity\AbstractEntityPersister.cs:line 3095
at NHibernate.Action.EntityDeleteAction.Execute() in d:\CSharp\NH\NH\nhibernate\src\NHibernate\Action\EntityDeleteAction.cs:line 70
at NHibernate.Engine.ActionQueue.Execute(IExecutable executable) in d:\CSharp\NH\NH\nhibernate\src\NHibernate\Engine\ActionQueue.cs:line 136
at NHibernate.Engine.ActionQueue.ExecuteActions(IList list) in d:\CSharp\NH\NH\nhibernate\src\NHibernate\Engine\ActionQueue.cs:line 126
at NHibernate.Engine.ActionQueue.ExecuteActions() in d:\CSharp\NH\NH\nhibernate\src\NHibernate\Engine\ActionQueue.cs:line 174
at NHibernate.Event.Default.AbstractFlushingEventListener.PerformExecutions(IEventSource session) in d:\CSharp\NH\NH\nhibernate\src\NHibernate\Event\Default\AbstractFlushingEventListener.cs:line 249
at NHibernate.Event.Default.DefaultFlushEventListener.OnFlush(FlushEvent event) in d:\CSharp\NH\NH\nhibernate\src\NHibernate\Event\Default\DefaultFlushEventListener.cs:line 19
at NHibernate.Impl.SessionImpl.Flush() in d:\CSharp\NH\NH\nhibernate\src\NHibernate\Impl\SessionImpl.cs:line 1489
at NHibernate.Transaction.AdoTransaction.Commit() in d:\CSharp\NH\NH\nhibernate\src\NHibernate\Transaction\AdoTransaction.cs:line 190
at Repositories.Repository.Delete(Task value) in ..\Repositories\Repository.cs:line 22
at TaskTest.TearDown() in ..\Tests\TaskTest.cs:line 76





With Cascade.All, simply calling delete on the parent object I get this exception:

Same as for Cascade.AllDeleteOrphan

After iterating through each of the children, recursively digging through those children's children and attempting to delete each child from the bottom up:

Same as for Cascade.AllDeleteOrphan

After iterating through the children, clearing each of their sets of children, then saving/deleting the parent I get this exception:

No exception: The parent gets deleted correctly but now I have orphaned objects that I do not want!




I have the looked through many blogs/stackoverflow questions/resource docs and have not really seen a solution to this issue.

Here are a few of the links I have dug through already:






Many of the posts mention inverting the relationship but setting .inverse and making the child own the relationship is totally not the goal here!

I have no idea what I am missing but hopefully this is something really simple to fix that I am overlooking. Any help will be much appreciated!

Answer Source

You are not missing anything. It is a combination of your mapping: a) child does not have a Parent mapped, b) child is versioned, c) collection is not set as inverse (because it cannot be managed by child without mapped parent) d) and finally, most likely due to a bug.

What happens, is that with versioning, any INSERT or UPDATE statement is followed by SELECT... to get the latest timestamp generated by DB Server. But this does not happen in one case:

  1. Collection parent is inserted
  2. parent version selected from DB
  3. child inserted
  4. child version selected from DB
  5. child updated (no inversion) to reference parent
    • -- NOTHING - child version IS NOT selected...

Because the child version after the relation update is different then the one just incremented in DB... later the StaleException is thrown.

The best you can do is extend the mapping to have a Parent... and make it inverse

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