I have two entities which have one-to-one relationship Site and Address. Both the tables have hibernate version column. i am using sitedao.save(siteEntity) to save, which saves both site and address.
When I am performing an update operation on site entity fields and persist, both site and address entity versions are getting updated because of #UpdateTimestamp annotation on lastModifiedAt column in the address table. This column makes the row dirty and increases the version column data (lastModifiedAt is coming from BaseEntity)
How can we avoid version increment in the address column
You could remove the CascadeType.MERGE between them, and save these two entities separately.
Then you could make a query to check if new address is different from the old one and only then save the address to update its version.
I got this solution from the below link.
https://docs.jboss.org/hibernate/orm/6.0/userguide/html_single/Hibernate_User_Guide.html#locking-optimistic
setting this annotation #OptimisticLock(excluded = true) on lastModifiedAt column solve this issue.
Related
I have an ASP.NET Core application that uses EF6 for dealing with a third-party application's database.
Everything is working as expected, but I'm unable to insert rows into a joining table.
I have two tables, Users and Groups, and a joining table GroupUser that identifies which users are members of which groups. Users has a PK of UserId, and Groups has a PK of GroupId.
GroupUser has only 3 columns: GroupId, UserId and another column (which is irrelevant for this post). The two foreign keys in this table identify a unique record.
Every time I try to insert into GroupUser, I get the inner exception
The table/view does not have a primary key defined. The entity is read-only
The error is correct. There is no PK, but both of the FKs are marked as keys in the model. Shouldn't VS be able to use those as a PK somehow?
The inserts used to work as some point, but required some manual modification of the .edmx file as XML in order to work. Unfortunately, our version control records containing this modification have been lost (and I wasn't the one originally working on this).
I've looked at and tried about a dozen articles around this, but they generally have to do with views instead of tables, so don't seem applicable to my case. The ones that did seem applicable didn't solve the issue.
The only other clue I have for a solution is this comment I found in the code:
// Important note: If you have updated the edmx file in the [redacted]
// project and suddenly start having problems, the edmx file may need to be
// edited as an xml file so that you can make changes necessary to make
// VS believe that the GroupUser table has a primary key. See revision #[redacted]
I'm able to insert into User and Group tables just fine, and as I've said, I don't have access to the revision log mentioned.
Edit: The database is for a third-party application, and unfortunately, it's not as simple as just modifying the table to add a PK. I wish it was. Problem would be solved. But I've been advised by the vendor not to make this change, as it may have unexpected consequences, and would void our support.
How can I 'trick' EF into thinking the table has a key? I'm also open to other workarounds. Modifying the DB structure is currently out of the question.
I am very new to EF programming.
My application gets the data from existing database. (DB first)
Now I have come to situation where I want to update my model to newer DB. basically the core schema is same as previous but has some modification in the table.
When I change the DB name for app.config and update the model it gives list of error
have I missed something?
When you do an update it merges the model you have with the DB that you update from. Additional columns are added to your existing entities but columns that you have removed from the DB are not removed from your entities and you need to remove these mappings yourself.
If you know which tables have columns removed it sometimes easier to delete the entity from your model and then do an update to reload it from the DB.
If you've don't know what tables or there have been many then it may be easier to delete all entities from your model and just do a full Update to reload the the new DB structure.
Ok, so I have 2 entities: Course and Industry
The industry entity is just a reference table which lists all available Industries that can be tagged to a course, to categorizing them. I put in a many to zero or one relationship (a course can choose to have an industry or not, while an industry can be tagged with many courses).
I know I've played around with the diagrams a bit, adding and removing associations in the past.
Now here is the odd part: The column mappings for Course has 2 similar columns, IndustryId and Industry_Id
I suspect it's from a past association, but thought EF would have taken care of that.
Here is the problem:
In my view that creates the course, the IndustryId is the property which needs to be populated. When I create new courses, I see the IndustryId in the database populated.
However, when I access Industry's properties through Course (Course.Industry.Description) nothing is populated. It can't seem to get the Industry entity.
I see the IndustryId populated in the db, so I tried to populate the Industry_Id column. That fixed it.
Weird enough, the property declared in the model is IndustryId, so that column is populated in the db. But when I try to get Industry entities through Course, it needs the Industry_Id, which I don't quite know where it is from.
Anyone have any ideas?
It sounds like in your updating from the database, you changed the column name on your tables from Industry_Id to IndustryId. The next time you updated from the database, EF5 (which can't determine that this is the same column, as it matches on names) dropped the mapping for Industry_Id, and added a new column called IndustryId.
However, you had already created the foreign-key mapping in your EDMX file based on the Industry_Id column - which is why you get the issue around needing it when loading related records.
In general, when using Database-First, whenever you rename a column in the database, you need to update your EF5 model and update / correct any such discrepancies.
I am using Database First EF to generate model from the existing database. When I first generated the models, it ignores only one of the table, the entity was not added to EDMX, no model file is created for the table and no context is created for the entity.
When I tried to explicitly add the table to EDMX (when generating the model, selected the specific table first and then updated the model with all the other tables from the database), it complained with the following error.
Two entities with possibly different keys are mapped to the same row. Ensure these two mapping fragments map both ends of the AssociationSet to the corresponding columns.
This specific table has two columns which are primary keys of some other tables and both the columns are specified as Primary keys for the table.
Am I doing something wrong or should I handle this table differently since it has two columns defined as Primary Keys? Any suggestions greatly appreciated!
You are not doing anything wrong. Your table is junction table for many-to-many relation. You don't need that table in the model because EF (in contrast to database) can handle many-to-many relation directly without any intermediate. The table is actually mapped on behind of the many-to-many relation - you will see that in mapping details window.
Btw. you are not using code first. Code first = no EDMX.
I have created a web site using mvc 3 and Ef code first , now after publishing the site and it's DB I have found out that I need to add a new columns to one of my DB table,
(the DB already has a lot of data in it )
should I add the columns direct to the DB or should I add to the class?
(just a simple string with get and set)
And how can I do it without losing my data in the DB ?
thanks
Adding the columns to the class should be enough. Evidence you can find here.
Here is the full list of changes that migrations can take care of automatically:
Adding a property or class
Nullable columns will be assigned a value of null for any existing rows of data
Non-Nullable columns will be assigned the CLR default for the given data type for any existing rows of data
Renaming a property or class
See ‘Renaming Properties & Classes’ for the additional steps required here
Renaming an underlying column/table without renaming the property/class
(Using data annotations or the fluent API)
Migrations can automatically detect these renames without additional input
Removing a property
See ‘Automatic Migrations with Data Loss’ section for more information
I suggest you to add the columns direct to the DB and to the class, and test it on the local machine.