Optional (nullable FK) and required (non-nullable FK) relationships, When dependents/children are loaded and tracked by the DbContext and when they exist only in the database, The default for required relationships like this is. to be much quicker than doing manual deletions for every single entity (most likely not as fast as the stored procedure but hopefully faster than manual deletions through-and-through). This is bad when we have clients trying to view their reports (which is what the API does). 3) File is parsed and new data is made into new entities. But when management wants to delete the customer records from primary registration table, the records from purchase table should also be deleted. DA924x said,  you need to alter your database table with DELETE CASCADE, like this: Our application is database first. The original approach was like this: This is called Cascade deleti… The OnDelete method takes a DeleteBehavior enum as a parameter:. Post.BlogId is a foreign key property, the value of which must match the Post.Id primary key of the post to which the blog belongs. If you want to add an on delete cascade to an existing foreign key constraint, you are going to need two statements.. This works great so far... but entity framework doesn't know about That way, it won't touch the database until much later in the process (after which running the stored procedure and saving the new entities will only take I would guess that the state of the drawing should be "deleted". >>Looks like I'm stuck deleting each and every entity manually in code. Hopefully that works. EF Core API builds and executes the DELETE statement in the database for the entities whose EntityState is Deleted. We have a web API that sometimes needs to access the database, and while we have a file being uploaded/parsed, it can't. it. Unfortunately I'm not familiar with the OnDelete-Method so I … Each table covers one of: Entities in the database that have not been loaded into the context, Deleting a blog will cascade delete all the related posts, Deleting the author of posts will cause the authored posts to be cascade deleted, Deleting the owner of a blog will cause the blog to be cascade deleted. In this article, we explored a few examples on DELETE CASCADE and UPDATE CASCADE rules in SQL Server foreign key. I don't bother with EF cascade deletes. 1) User uploads file. The following table shows the result of each OnDelete value on the foreign key constraint created by EF Core migrations or EnsureCreated. This document describes cascade deletes (and deleting orphans) from the perspective of updating the database. Check your database documentation for the specific differences between ON DELETE NO ACTION and ON DELETE RESTRICT on your database system. EF Core configures these behaviors based on the cascade delete behavior in the EF Core model when a database is created using EnsureCreated or EF Core migrations. If possible, could you please share a simple demo, which could reproduce the issue via OneDrive. The exact timing of when cascading behaviors happen to tracked entities can be controlled using ChangeTracker.CascadeDeleteTiming and ChangeTracker.DeleteOrphansTiming. So in that case a single delete query of master table can delete master tables data as well as child tables ... not working in sql 2008. I was afraid someone might say that. Introduction. All other values will configure the database to not cascade any changes. It makes heavy use of concepts introduced in Change Tracking in EF Core and Changing Foreign Keys and Navigations. For example, when an author is deleted, it will remove all the related books automatically as … Here the parent table is the table specified in the REFERENCING clause of the definition of an enabled foreign key constraint, and the child table is the table on which the enabled foreign key constraint is defined. The behaviors of ON DELETE NO ACTION and ON DELETE RESTRICT in relational databases are typically either identical or very similar. The department will not be set to null. Many database systems also offer cascading behaviors that are triggered when an entity is deleted in the database. Consider an example of Customer Registration. And by a C# transaction, I mean this: ^ This runs on every request/response round from the client to the server (like when the user uploads a files to the point when the data from the file is saved to the database). You’ll be auto redirected in 1 second. Cascade ; SET NULL ; SET Default; It is not necessary that the same rule be applied for both update and delete operations. The statement has been terminated. When a customer gets registered in a table, some of the records also get stored into the dependent table like their purchasesin purchase table. Then the delete successfully removes both the city and the zip code. You can handle the cascade only on the Entity DbContext with OnModelCreating. For example, if you didn't define the Department.InstructorID property as nullable, EF would configure a cascade delete rule to delete the department when you delete the instructor, which isn't what you want to have happen. SaveChanges in this case will delete just the blog, since that's the only entity being tracked: This would result in an exception if the foreign key constraint in the database is not configured for cascade deletes. If we know that the database is configured like this, then we can delete a blog without first loading posts and the database will take care of deleting all the posts that were related to that blog. Instead you will need to rename the table, create a new table with the foreign key, and then copy the data into the new table. Unable to save changes because a circular dependency was detected in the data to be saved: 'ForeignKey: Profile.InstagramId ... Those tables with a FK should have ON DELETE CASCADE qualifiers. For cascade delete, this severing happens because the principal/parent is itself deleted. Given all this, there are a number of approaches we tried. The department's employee will be nullified, or in the case of a to-many rule, the department's employees will have an entry removed. You can not use the ALTER TABLE statement to add a foreign key with cascade delete in SQLite. The Delete value is commonly used when you implement data purging mechanisms, where you need automatic cascade delete between the whole model.. With large files, it will be blocked I figured that if I let EF handle all the work of deleting entities (starting with manual deletions on just a few at the topmost level of the hierarchy), then it's bound entities manually is exceptionally slow. In the following example, a cascade delete is configured on the relationship between Blog and Post, so the post entity is deleted from the database. The difference, when there is one, is when the database checks the constraints. This can result in circular cascade delete rules, which will cause an exception when you try to add a migration. Prior to EF Core it didn't have a name and was not possible to change. Cascade delete on one-to-one relationships not working #147. Databases can also be configured to cascade nulls like this when a principal/parent in an optional relationship is deleted. Severing a relationship is not valid here since the dependents/children are not loaded. The alter table command lets you do quite a bit. There are two ways to handle this situation: Taking the first approach with our example, we could make the blog-owner relationship optional by giving it a nullable foreign key property: An optional relationship allows the blog to exist without an owner, which means cascade delete will no longer be configured by default. Since data purging mechanisms are typically handled by an asynchronous process (Timer or BPT), performance is not a concern. This means that if the application loads all relevant dependent/child entities into the DbContext, as is shown in the examples above, then cascading behaviors will be correctly applied regardless of how the database is configured. Yes, ON UPDATE CASCADE will update only the columns used in the FK definition. 2) Delete stored procedure runs to delete old data. Cascading delete refers to the action of removing records associated by a foreign key relationship to a record that is the target of a deletion action. Letting the DB engine do the cascading deletes is 10,000 time more faster than code you have written to do it or letting EF do it. Consider this simple model where Blog is the principal/parent in a relationship with Post, which is the dependent/child. Change one or more of the relationships to not cascade delete. The EF Core in-memory database does not currently support cascade deletes in the database. Conclusion. I suppose this is why setting cascade on delete in the data model doesn't work? Here's a super simplified version of my model: User {UserID, Name} Recipe {RecipeID, UserID} Ingredient {IngredientID, UserID} RecipeIngredient {RecipeID, IngredientID} *RecipeIngredient is … Even though the stored procedure is fast, it's the parsing of the file that takes time (can take on the order of 10 minutes or more), and during that time, The child/dependent can be deleted 2. The issue was that this whole procedure is done in a transaction (C#, not SQL), which locks the database. But I'm not sure if this is the best way. Everyone agreed (and accepted) that this would be somewhat slower than running the stored procedure, but the goal was to minimize the time during which the database is blocked EF Core always applies configured cascading behaviors to tracked entities. Specify foreign key for the details tables which references to the primary key of master and set Delete rule = Cascade . is NOT what's supposed to happen if EF has cascading on delete working properly. If you use entity framework database first, As DA924x said,  you need to alter your database table with DELETE CASCADE, like this: MSDN Community Support But when it comes to altering existing constraints, there is not much you can do. For example: See Relationships for more information on configuring relationships between entity types. 1) Shows how DELETE cascade works -- Parent table CREATE TABLE supplier ( supplier_id numeric(10) not null, supplier_name varchar2(50), contact_name varchar2(50), CONSTRAINT supplier_pk PRIMARY KEY (supplier_id) ); -- children table with foreign key CREATE TABLE products ( product_id … For example, using the model above, the following table is created for posts when using SQL Server: Notice that the foreign key constraint defining the relationship between blogs and posts is configured with ON DELETE CASCADE. It is now known as ClientSetNull as described in the next section. 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