I have an entity called Books that can have a list of more books called RelatedBooks.
The abbreviated Book entity looks something likes this:
public class Book
{
public virtual long Id { get; private set; }
public virtual IList<Book> RelatedBooks { get; set; }
}
Here is what the mapping looks like for this relationship
HasManyToMany(x => x.RelatedBooks)
.ParentKeyColumn("BookId")
.ChildKeyColumn("RelatedBookId")
.Table("RelatedBooks")
.Cascade.SaveUpdate();
Here is a sample of the data that is then generated in the RelatedBooks table:
BookId RelatedBookId
1 2
1 3
The problem happens when I Try to delete a book. If I delete the book that has an ID of 1, everything works ok and the RelatedBooks table has the two corresponding records removed. However if I try to delete the book with an ID of 3, I get the error "The DELETE statement conflicted with the REFERENCE constraint "FK5B54405174BAB605". The conflict occurred in database "Test", table "dbo.RelatedBooks", column 'RelatedBookId'".
Basically what is happening is the Book cannot be deleted because the record in the RelatedBooks table that has a RelatedBookId of 3 is never deleted.
How do I get that record to be deleted when I delete a book?
EDIT
After changing the Cascade from SaveUpdate() to All(), the same problem still exists if I try to delete the Book with an ID of 3. Also with Cascade set to All(), if delete the Book with and ID of 1, then all 3 books (ID's: 1, 2 and 3) are deleted so that won't work either.
Looking at the SQL that is executed when the Book.Delete() method is called when I delete the Book with an ID of 3, it looks like the SELECT statement is looking at the wrong column (which I assume means that the SQL DELETE statment would make the same mistake, therefore never removing that record). Here is the SQL for the RelatedBook
SELECT relatedboo0_.BookId as BookId3_
, relatedboo0_.RelatedBookId as RelatedB2_3_
, book1_.Id as Id14_0_
FROM RelatedBooks relatedboo0_
left outer join [Book] book1_ on relatedboo0_.RelatedBookId=book1_.Id
WHERE relatedboo0_.BookId=3
The WHERE statment should look something like this for thie particular case:
WHERE relatedboo0_.RelatedBookId = 3
SOLUTION
Here is what I had to do to get it working for all cases
Mapping:
HasManyToMany(x => x.RelatedBooks)
.ParentKeyColumn("BookId")
.ChildKeyColumn("RelatedBookId")
.Table("RelatedBooks");
Code:
var book = currentSession.Get<Book>(bookId);
if (book != null)
{
//Remove all of the Related Books
book.RelatedBooks.Clear();
//Get all other books that have this book as a related book
var booksWithRelated = currentSession.CreateCriteria<Book>()
.CreateAlias("RelatedBooks", "br")
.Add(Restrictions.Eq("br.Id", book.Id))
.List<Book>();
//Remove this book as a Related Book for all other Books
foreach (var tempBook in booksWithRelated)
{
tempBook.RelatedBooks.Remove(book);
tempBook.Save();
}
//Delete the book
book.Delete();
}
Rather than setting the cascade attribute, I think you need to simply empty the RelatedBooks collection before deleting a book.
book.RelatedBooks.Clear();
session.Delete(book);
Cascading deletes is not typically done in a many-to-many relationship because it will delete the object at the other end of the relationship, in this case a Book.
This just got updated:
http://fluentnhibernate.lighthouseapp.com/projects/33236/tickets/115-self-referencing-relationships
Related
Is there any simpler way to delete the records of table with are mapped by #OneToMany and #ManyToOne JPA mapping. Currently I am using PostgreSQL as my database. There are 1000 records ranging from 0 to 999 which I want to delete, and rest I want to keep. As deleting every record with deletion of there references(foreign key) will be very hectic. Just want a simpler way to do this.
You can always execute a DELETE query in JPA:
int rowsDeleted = entityManager
.createQuery("DELETE FROM MyEntity WHERE id >= 0 AND id <=999")
.executeUpdate();
If there are foreign keys, you need some extra work:
int childRowsDeleted = entityManager
.createQuery("DELETE FROM MyChildEntity WHERE parent.id >= 0 AND parent.id <=999")
.executeUpdate();
int rowsDeleted = entityManager
.createQuery("DELETE FROM MyEntity WHERE id >= 0 AND id <=999")
.executeUpdate();
If there are many foreign keys, perhaps you can consider JPA cascade remove:
#OneToOne(cascade={CascadeType.REMOVE})
and then entityManager.remove() each entity but this will have performance implications since you will end up with many DELETE queries, each deleting a single row.
Got this with introducing #DeleteMapping, and it worked without even using
" #OnDelete(action = OnDeleteAction.CASCADE)" this annotation above the mapped variable declaration in the child class
[https://www.callicoder.com/hibernate-spring-boot-jpa-one-to-many-mapping-example/#get-paginated-posts-get-postspage0size2sortcreatedatdesc], We can follow this link to get a complete overview.
#DeleteMapping("/posts/{postId}")
public ResponseEntity<?> deletePost(#PathVariable Long postId) {
return postRepository.findById(postId).map(post -> {
postRepository.delete(post);
return ResponseEntity.ok().build();
}).orElseThrow(() -> new ResourceNotFoundException("PostId " + postId + " not found"));
}
I have three tables. I want to display all data from cms_planner table together with Topic Name from cms_topic table. To achieve that, I need to go through the cms_subject table.
I want to use belongsToMany but I already have cms_subject table that holds the foreign key for cms_planner and the foreign key for cms_topic. The table name does not represent pivot key.
I also want to use hasManyThrough but it doesn't work. I'm thinking to inverse the hasManyThrough.
How can I achieve that?
1. CmsPlanner
i. planner_id
ii. subject_id
iii. date_start
2. CmsSubject
i. subject_id
ii. topic_id
3. CmsTopic
i. topic_id
ii. topic name
In CmsPlanner model
public function subject(){
return $this->hasManyThrough(
'App\CmsTopic',
'App\CmsSubject',
'topic_id', 'topic_id', 'planner_id');}
In CmsPlanner controller
CmsPlanner::with('subject')->get();
Add this relation on CmsSubject
public function cmsTopic()
{
return $this->belongsTo('App\Models\CmsTopic', 'topic_id', 'topic_id');
}
then add following relation on CmsPlanner
public function cmsSubject()
{
return $this->belongsTo('App\Models\CmsSubject', 'subject_id', 'subject_id');
}
to get data
$cms_planner = CmsPlanner::with('CmsSubject')->where('id', $planner_id)->get();
'user' => $this->business->user
I have a database that has a parent-child look up for my drop down values, there is a domain table which represents what type of drop down it is ie "TITLE", "MARITAL_STATUS", "COUNTRY" and there is look up for the values associated with each of these drop downs that we call domain values
EG
TITLE (Domain table)
MR (Domain Value table)
MRS (Domain Value table)
MISS (Domain Value table)
DOCTOR (Domain Value table)
MARITAL_STATUS (Domain table)
SINGLE (Domain Value table)
MARRIED (Domain Value table)
DIVORCED (Domain Value table)
I find myself writing ugly code which exposes the under lying implementation similar to below
using (var db = new OrderContext())
{
...
var maritalStatusId = (
from sp in db.DomainValues
where sp.ShortCode == "MARRIED"
where sp.Domain.ShortCode == "MARITAL_STATUS"
select sp.Id
).FirstOrDefault();
if maritalStatusId != 0)
{
orderStore.maritalStatus = maritalStatusId;
}
...
db.OrderStores.Add(orderStore);
db.SaveChanges();
}
Is it possible to write code that looks similar to this
using (var db = new OrderContext())
{
...
orderStore.maritalStatus = new MaritalStatus { ShortCode = "MARRIED" }
...
db.OrderStores.Add(orderStore);
db.SaveChanges();
}
, where a navigation property handles the insert?
If so how do I set this up?
Any links to articles on this would be good too.
You can keep a cache with the different values of your dropdowns, that seems reasonnable, or you can use enumeration if the values are not dynamic.
Another solution would be to have the shortcode field to be the primary key of the table, all your problems would be resolved.
Using ObjectContext. I'm wanting to do this by passing an SQL query via the ExecuteStoreCommand since I don't fancy retrieving all relevant entities just for the sake of deleting them after.
The Category table is as so:
CatID | CatName | ParentID
Where CatID is the primary key to the ParentID FK
I am wishing to delete a category and also all those that
are under it. Can be 2+ levels deep of sub cats, so different ParentID's
Thought I could do it as below and just set "cascade" on delete option
for the foreign key in the database, but it won't let me and it does not appear to want to
cascade delete down by using the CatID - ParentID relationship and the query gets
stopped by this very FK constraint.
public RedirectToRouteResult DelCat(int CatID)
{
if (CatID != 0)
{
_db.ExecuteStoreCommand("DELETE FROM Categories WHERE CatID={0}", CatID);
_db.SaveChanges();
}
return RedirectToAction("CatManage");
}
Recursive CTE allCategories produces list of all categories in hierarchy. Delete part, obviously, deletes them all.
; with allCategories as (
select CatID
from Categories
where CatID = #CatID_to_delete
union all
select Categories.CatID
from allCategories
inner join Categories
on allCategories.CatID = Categories.ParentID
)
delete Categories
from Categories
inner join allCategories
on Categories.CatID = allCategories.CatID
Try it with select * from allCategories, though, to check first.
There is TEST # Sql Fiddle.
Why not just send two statements in your batch?
DELETE Categories WHERE ParentID = {0};
DELETE Categories WHERE CatID = {0};
If the framework you're using "won't let you" do that, then do this right: put your logic in a stored procedure, and call the stored procedure.
SQL 2008 | .NET 4.0 | NHibernate 3.1 | NHibernate.Castle 3.1 | Castle.Core 2.5.2
So I have a linking table with metadata, like the author of this question NHibernate Mapping a Many to Many with Data on Join Table
Initially, I mapped just like the answer to this question as it seemed the most parsimonious way to handle it. However, after turning on show_sql and observing what was going on, the ID lookups ended up yielding N+1 queries where N is the number of associations.
Observe this example database that is analogous to my actual data, defined in sql-like syntax
CREATE TABLE [User]
(
Id int PRIMARY KEY
)
CREATE TABLE UserPref
(
Id int PRIMARY KEY,
Name varchar(32)
)
CREATE TABLE UserPrefAssociation
(
UserId int,
PrefId int,
Value varchar(32)
)
I hacked the following code together with this User one-to-many object mapping IList<UserPrefAssociation> Preferences { get; set; }
public IDictionary<string, string> GeneratePrefDict()
{
return Preferences
.ToDictionary(i => i.UserPref.Name, i => i.Value);
}
Sure, this works great, but as mentioned before, each i.UserPref.Name, is an additional query to SQL.
After playing in SQL, I have found the query that accomplishes what I want. My question then becomes how can I do this with NHibernate?
SELECT UserPref.Name, UserPrefAssociation.Value
FROM [User]
INNER JOIN UserPrefAssociation ON [User].Id = UserPrefAssociation.UserId
INNER JOIN UserPref ON UserPrefAssociation.UserPrefId = UserPref.Id
WHERE [User].Id = 1
~~~~SOLVED~~~~~
using NHibernate.Linq;
...
public IDictionary<string, string> GeneratePrefDict(ISession s)
{
return
(from entry in s.Query<User_UserPref>()
where entry.User == this
select new
{
key = entry.UserPref.Name,
value = entry.Value
})
.ToDictionary(i => i.key, i => i.value);
}
Generates this SQL
NHibernate: select userpref1_.Name as col_0_0_, user_userp0_.Value as col_1_0_ f
rom User_UserPref user_userp0_ left outer join UserPref userpref1_ on user_userp
0_.UserPrefId=userpref1_.Id where user_userp0_.UserId=#p0;#p0 = 1 [Type: Int32 (
0)]
Which is better than N+1 queries, and solves my issue.
I think you can achieve what you are wanting with Futures and QueryOver. Take a look at the following article:
Fighting cartesian product (x-join) when using NHibernate 3.0.0
If you can't visualize how to accomplish what you need from the above I can tailor that example more to your needs.