Recently I have faced issue with EF codefirst DB migrations. We have used MigrateDatabaseToLatestVersion for DB initializer.
Database.SetInitializer(new MigrateDatabaseToLatestVersion<TestDataContext, MyConfiguration>());
internal sealed class MyConfiguration : DbMigrationsConfiguration<TestDataContext>
{
public Configuration()
{
AutomaticMigrationsEnabled = true;
AutomaticMigrationDataLossAllowed = true;
...
Issue is that - we accidentally ran old DB migration file using the below command :
Update-database -TargetMigration some_old_test_migration_cs_file
This caused us to loose latest entity schema changes and we were unable to push latest changes to database. After wasting a lot of time in troubleshoot, we fixed that issue by deleting migration history from the table __MigrationHistory.
My question is - Should we also add migration scripts whenever entity (code level) changes though we have enabled the automatic migrations?
What would be the best practice around this?
If you're using Automatic Migrations, you shouldn't need to code any explicit migrations yourself. Entity Framework will automatically update the database to match the current state of your entities when you create a context.
Related
We wish to get rid of 100s of migration classes as DB schema in production is final.
Here are the steps I followed:
Delete Migrations folder.
Add-Migration -??
What command line switches, could help us?
EDIT:
If all goes well Up() method of migration should be empty right? For
example following is wrong generation on Add-Migration. Because if we
execute the project we will get duplicate table errors.
public partial class Sanity : DbMigration
{
public override void Up()
{
CreateTable(
"dbo.AccountPreferences",
c => new
{
AccountID = c.Guid(nullable: false),
}
.... for 1000s of tables
}
}
A clean migration would be something: when trying Add-Migration on subsequent changes, should not be getting any error.
Unable to generate an explicit migration because the following
explicit migrations are pending: [201712281054591_Sanity]. Apply the
pending explicit migrations before attempting to generate a new
explicit migration.
As you can see if we happen to execute Update-Database will get table already exist error.
Are we forced to always retains all migration copies?
See if this can help:
MVC3 and Code First Migrations - "model backing the 'blah' context has changed since the database was created"
Entity framework code first - how to run Update-Database for production database
How to delete and recreate from scratch an existing EF Code First database
note:
I'm writing this from memory, if you have issues let me know and I'll recheck exactly.
Also, my knowledge on this is from slightly older versions of EF as I haven't done much work there recently, but I doubt much has changed.
From what I can tell, if you want to...
a) keep the db,
b) clean your project migrations,
c) have the 2 'match', be in sync:
do the following:
- Remove the migration folder (your project)
- Run Add-Migration Initial - then should add one migration
- caution: it is safe but do backup, change connection string etc. before the next step
- Run Update-Database -Script - that doesn't update the db but creates the SQL script, including the migration table
- find the INSERT INTO [__MigrationHistory] records, just run those (on your db), insert them into the database
...then test with Add-Migration again, to see if it is going to make anything, should yield no new migrations, empty one.
Please read through the first link above and adjust approach as needed.
I'm sure there might be easier, shorter ways to do this (via PM console) but unaware of it at the moment.
Open your database.
Clear table __MigrationHistory
Remove migrations in the folder
Run Add-Migration MigrationName
Almost the same as accepted one, but no scripting the initial migration.
Drop the __MigrationHistory db table
Remove all the migration files in the Migrations folder
Run Add-migration Initial in Package Manager Console
Comment out the code inside of the Up method in the Initial Migration
Run Update-database in PM Console (just to create a Migration Entry)
Remove comments in the Initial migration
Wonder how long it will be "final" ?
Use:
Add-Migration Initial
After removing the migrations folders
There was a breaking change so we decided to reset migrations, but now If we don't put the -EnableAutomaticMigrations option Enable-Migrations doesn't work.
My connection string is in my web project that is set as the startup project.
This are the steps we took:
First We deleted the Migrations folder and the database completely.
Then When we do:
enable-migrations
We get:
Checking if the context targets an existing database...
Unable to update database to match the current model because there are pending
changes and automatic migration is disabled. Either write the pending
model changes to a code-based migration or enable automatic migration.
Set DbMigrationsConfiguration.AutomaticMigrationsEnabled to true to
enable automatic migration.
I don't understand this error, there is no database, there are no migrations, to what pending changes does it refer to? (I dont even have pending chanves in git)
If then We do
enable-migrations -EnableAutomaticMigrations
It works, but when We follow it with:
Add-Migration InitialCreation
It creates an Empty InitialCreation migration and it creates the database with the tables that correspond to my model. But doing this We can't get the scripts for creating the database for the first time. I don't get what is going on.
It seems the first time it uses some Automatic migration.
Why can't We enable-migrations without -EnableAutomaticMigrations?
Update
After talking with Steve Green, I think it could be useful to add part of my DbContext and Initializer
public class ApplicationDatabaseContext : DbContext
{
public ApplicationDatabaseContext()
: base("MyConnectionStringName")
{
Database.SetInitializer<ApplicationDatabaseContext>(new ApplicationDataInitializer());
if (!Database.Exists())
{
Database.Initialize(true);
}
}
And my DatabaseInitializer:
public class ApplicationDataInitializer : CreateDatabaseIfNotExists<ApplicationDatabaseContext>
{
protected override void Seed(ApplicationDatabaseContext context)
{
base.Seed(context);
CreateData(context);
}
private void CreateData(ApplicationDatabaseContext context)
{
//Add data here
context.SaveChanges();
}
}
First, make sure you have the initializer MigrateDatabaseToLatestVersion set.
Second, You should not need to enable automatic migrations. To reset migrations you don't have to delete the entire folder (especially if you've done some seeding or other customizations in the Configuration() class). Just delete the individual migrations then add a new baseline migration:
add-migration MyStartPoint -IgnoreChanges
This will take a snapshot with no code in the Up() since you don't really need that to generate a script to create the database. So now update-database -Script -SourceMigration $InitialDatabase should create a script you can use to create a new database.
Another option is to use an initializer like CreateDatabaseIfNotExist which will do exactly that.
I successfully created an Entity Framework Core migration and updated the database with it.
Then after I added another class, I created a second migration called "update1" which created a class of the same name from the command line tools.
However, when I attempt to update the database, it fails.
Here is the commands I used
dotnet ef migrations add update1 -c MyDbContext
dotnet ef database update update1 -c MyDbContext
and it failed with
There is already an object named MyTable in the database
which is a table which was created in the initial migration.
How can I tell it to either ignore the error, or else to only attempt to run the update1 migration?
Edit: deleting the table that was already there caused this odd behavior to stop happening and now it works as expected.
Thanks
You have to remove the unwanted migration from the __MigrationHistory table.After that you can run your latest migration.This is happened due to you have manually deleted the table.B'cos EF doesn't know anything about your manual operations hence __MigrationHistory table still exist your old migration details (i.e. manually deleted table's record).
In my case I used Ubuntu, EF 6 and the database was in the docker and it's doesn't updated DB.
I added --connection attribute and it's works, an example:
sudo dotnet ef database update --connection
"Server=localhost;Database=temp;User Id=sa;Password=xxxxxxx;"
End of long day of testing various scenarios where I don't have to recreate a production database...
We started off with EF, and didn't get wise enough during development to move from automatic migrations to named migrations. Now I'm trying to rewind the clock, and create an initial migration that aligns with the production database.
Is this possible to align a model has with an automatic migration has in the migration table?
Should I just create an empty migration to get started with named migrations? My only problem with this is how to create the DB when a new developer joins... I could simply restore the db, and then apply migrations, but that ruins a beautiful EF migration story!
Delete the production DB, create, and write a script to re-import the data (sounds hacky).
Another wrinkle - the DB was created with EF5, and we are now developing with EF6.
Thanks in advance for your help.
It should be possible:
Delete the __MigrationHistory table
Delete any migrations in your project
Disable automatic migrations in your migrations configuration class
Add-Migration InitialCreate
Update-Database -Script
Execute the portion of the script that creates the __MigrationHistory table and inserts a row into it
Repeat steps 1 & 6 for any other existing databases
I also strongly recommend reading Code First Migrations in Team Environments.
If you don't like step 7 of bricelam's answer. Then keep reading.
Because upgrading from automatic migrations to manual can also be automated. And you don't need to delete the migrationhistory table like bricelam says.
In this case I assume you have one development machine, and multiple other (development) machines where databases already exist.
On your development machine you move your database into a safe location (keeping it safe to test your automatic upgrade procedure). (You might want to make sure your code is in the same exact state as all the database which you want to upgrade).
Delete any migrations in your project (you should't have any yet)
Disable automatic migrations in your migrations configuration class
Add-Migration InitialCreate
Put a backup (copy!) of your database back into place
On startup of your application (or your upgrade app) you do something like:
using (var db = new YourDatabaseContext())
{
InitialCreate.SkipInitialCreate = db.Database.Exists();
}
And in your InitialCreate you add something like:
public static bool SkipInitialCreate = false;
public override void Up()
{
// Skip initial create
if (SkipInitialCreate)
return;
This assumes that if a database exists it has the same structure as the one you had on your dev machine. Of course this could be way more complex than that for you. For more control you could inspect DbMigrator object for your config, and skip more than one migration. (would have been nice if you could query the hash of the model in the DbMigrator...)
After the code in step 4 add something like:
var configuration = new YourDatabaseConfiguration();
var migrator = new DbMigrator(configuration);
migrator.Update();
Start your application on your dev machine to test the upgrade. Your history table should have an automaticmigration record and a initialcreate record.
If everything works out you should be able to simple deploy and run the app on machines where the db already exists.
One very important aspect (and maybe the reason bricelam says you needed to delete the history table) is that if the AutomaticMigration record in that table is newer than one of your manual migrations you are going to have a Bad time. Because the migrator uses the dates to sort out the work it needs to do.
So if there are systems out there still automatically upgrading to the newest auto-upgrade model, then you are in a bit of a pickle.
I'm using EF 5. We are looking to convert our project to use code-first migrations.
Originally in our DBContext file we had an IDataBaseInitializer implementation that creates the DB if it doesn't exist (using context.Database.Create).
I wanted to test out the migration concept so I originally ran the commands:
Enable-Migrations -ProjectName MyProjectName
(This successfully created a Migrations folder with a Configuration.cs file)
Add-Migration Initial -ProjectName MyProjectName
(This successfully created a script file which matched my model classes)
At this point I wanted to try testing upgrade scenario so I created a tmp field on my model and reran the Add-Migration command which seemed to work as expected.
However at this point I wanted to reset my state. I've reverted all my changes in VS, removed the files from the Migrations folder from disk, tried removing the __MigrationsHistory table from my DB (and also completely deleting the DB). No matter what I do I can't get a new Add-Migration to create a script that includes my initial state. It always appears as this... this is my test value that I created originally.
public partial class Initial : DbMigration
{
public override void Up()
{
DropColumn("dbo.EventTrackingRecords", "TestValue");
}
public override void Down()
{
AddColumn("dbo.EventTrackingRecords", "TestValue", c => c.String());
}
}
I don't understand where it's keeping this initial information. The only other thing that I found interesting is that if I run my program after deleting the DB, it recreates my DB as I would expect based on the model, but it also creates a __MigrationHistory table! I don't understand how the context.Database.Create() command is doing this.
EF creates the __MigrationHistory table to keep your DB up to date, and warn you if it's not.
When you edit something in your models, and run the add-migration, you have to run update-database to be able to create a new migration. EF won't allow you to have pending migrations while creating new ones.
So, if you add a property to one of your models, and then create a migration, you have to update the database before creating a new migration where you delete the property.
Hope this helps.