I'm developing an ASP.NET MVC 4.5 project using EF 6 Code First to an Existing Database. I would like to create some new tables with foreign key relationships to one of the tables in the dbcontext I've created. I've altered and added columns in that original table, creating several migrations. There is real data in that table.
I would prefer to create the new tables in the database, but don't see how EF would generate a model for me. I can code the model myself, but don't see any documentation about how I would add it to the context class generated by EF. And then the migrations would be out of whack.
So I'm thinking that the best thing to do would be to delete all the migrations, delete the context class and drop the migrations table. Then I could start from scratch with an initial migration. Am I missing some gotcha? Is there a better way?
FWIW to others facing this dilemma, I figured it out. First I got rid of all the migrations, following the 100+ up-voted answer here: Reset Entity-Framework Migrations
Second, I created new the tables and constraints I needed in the database.
Third, I created a new entity in my solution and generated model classes from the database. I changed calls from the old entity to the new entity.The generator overwrote the model for the original table, but since I have all the annotations in version control, it is trivial to paste them in.
If I need to, I can enable migrations again.
Hope this helps.
Related
This is actually the first time I'm posting something here. The problem I have is driving me crazy since I know such functionality exists elsewhere.
I'm trying to find a way to create new tables on the fly on node js using sequelize without having to restart the database (a DB implemented with SQL).
Moreover, I also need to create new associations between those new table and existing ones.
Why do I need this:
I'm creating a crm and one of the functionalities I want to add is to let users create new types of objects that could have fields referencing to other preexisting ones.
And I can't just restart the whole database everytime a user is creating a new object or fields.
If you guys know how to achieve that or maybe advising me to build the database with another language I'll go for it.
Thanks!
I am trying out JHipster (version 6.4.1) using a Monolith and disk-based H2 database. I have created some entities in JDL and have the basic CRUD webpages working. Now that I feel comfortable with the process, I want to add fields and rename others. I figured I could simply update the JDL, re-import the JDL, start the application, and see the result of my changes. What I see is ValidationFailedException from Liquibase and the application throwing HTTP 500 errors due to database problems.
I have looked all over for guidance on the proper process for handling this seemingly common development scenario. Most of the places I have looked for guidance (such as https://www.jhipster.tech/creating-an-entity) discuss importing JDL as a one-time-only operation and do not discuss how to incrementally change and import the JDL.
I have tried a number of suggestions as seen on SO, such as not overwriting the changelogs, doing a liquibase:diff, and adding that to master.xml. This still causes the ValidationFailedException. In the master.xml I see the comment <!-- jhipster-needle-liquibase-add-changelog - JHipster will add liquibase changelogs here --> which leads me to believe that JHipster should be doing the heavy lifting, but I am just missing a step.
I am by no means a JHipster nor a Liquibase expert, but I want to learn. How I can perform simple entity updates without a huge hassle?
[Update with more detail]
After re-importing the updated JDL, I have managed to get rid of the DB Validation Errors by blowing away the database with rm -rf target/h2db/db.
I'm happy with my changes and feel like a commit is in order. What I see is
master.xml is unchanged
the changelog from the first JDL import has been modified to include the updates I made
If I understand how liquibase works, I would have expected
None of the existing changelogs would be touched
A brand new changelog file would be created that contained just the JDL changes I made this round
master.xml to have changed only in that it would contain an additional changelog entry, pointing to the file created in item 2
Am I misinterpreting how Liquibase represents evolution of the DB schema?
It appears that the page you referenced does have some instructions for updating entities. Farther down the page I saw this:
Updating an existing entity
The entity configuration is saved in a
specific .json file, in the .jhipster directory. So if you run the
sub-generator again, using an existing entity name, you can update or
regenerate the entity.
When you run the entity sub-generator for an existing entity, you will
be asked a question ‘Do you want to update the entity? This will
replace the existing files for this entity, all your custom code will
be overwritten’ with following options:
Yes, re generate the entity - This will just regenerate your entity.
Tip: This can be forced by passing a --regenerate flag when running
the sub-generator
Yes, add more fields and relationships - This will
give you questions to add more fields and relationships
Yes, remove fields and relationships - This will give you questions to remove
existing fields and relationships from the entity
No, exit - This will exit the sub-generator without changing anything
You might want to
update your entity for the following reasons:
You want to add/remove fields and relationships to an existing entity
You want to reset your entity code to its original state
You have updated JHipster, and would like to have your entity generated with
the new templates
You have modified the .json configuration file (the
format is quite close to the questions asked by the generator, so it’s
not very complicated), so you can have a new version of your entity
You have copy/pasted the .json file, and want a new entity that is
very close to the copied entity
I want to store information in some activities that are modified versions of activities imported from an existing database (ecoinvent).
I know we can add fields to activities created from scratch (example). (I guess this is because the structure of the database has not yet been defined...) but is there a way of adding it to activities of an already defined database without breaking it?
The way around I found is to add entries to the author dict, which I can easily access later on. e.g.
act['author']['scenario']='myscenario'
but I admit it is not a very elegant solution.
You can just add whatever data you want. Brightway is a (semi-)schemaless database for exactly this reason.
act['foo'] = 'bar'
act.save()
https://azure.microsoft.com/en-us/documentation/articles/mobile-services-dotnet-backend-use-existing-sql-database/
I have been following this tutorial but it ends up creating a new table emptying all the data. How do I make it uses existing values inside an existing table?
The tutorial indeed populate example data using Database.SetInitializer(new ExistingInitializer()); but it wont make new DB.
Make sure you have correct connection string Name=MS_TableConnectionString (step 4 in Exploring the existing database model) so it points out to you existing DB
Edit:
First of all, comment out database seeder Database.SetInitializer(new ExistingInitializer()); and to query your existing data use GetAllMobileCustomers in MobileCustomerController or GetAllMobileOrders in MobileOrderController it will give you IQueryable of MobileCustomer of MobileOrder object, use that object as you wish
With Entity Framework it is possible to enable migrations and create migration steps. But is there an intermediate way where it is possible to change the models, and take care of database schema changes yourself? I don't want to drop the database, because there are future production schenario's.
Now - without enable migrations - I use a code first, and when I create another property in a DbSet - lets assume for example in table 'ExistingTable' int NewField {get; set;}
And when in SQL I update my schema with
Alter table ExistingTable add column NewField int not null
the database knows existence of the new field, the Entity Framework / C# knows the property, but when running, there is some hidden check that still want's to drop my database because of the model change.
Question: can I overwrite a certain setting, in such a way that intial 'Code First' can be transformed to database first?
Removing the __MigrationHistory table from the database (Azure) did work fine for me. I made my (simple) database changes myself and published the code. It all runs fine. There is an alternative see EF Code First Migrations Deployment to an Azure Cloud Service. For a simple one-way patch (and no change history needed) removing the __MigrationHistory works fine.