I am trying to use migrations with a existing database and to create a new one, if not exists.
The EF Core documentations says:
If you created the initial migration when the database already exists, the database creation code is generated but it doesn't have to run because the database already matches the data model. When you deploy the app to another environment where the database doesn't exist yet, this code will run to create your database
From EFCore docs
I did initial migrations, it creates a up and down methods to create my tables. When I run it to a new database (new database name in connection string) it creates the database and tables as expected.
But if I run it to an existing database (not created by migrations), it fails at the first up method that tries to create a table that already exists, and the migrations stops to run.
Docs says "it doesn't have to run", but first thing migrations is doing is try to create an existing table.
How to prevent migrations to try to create existing tables? There is something like "create if not exists" built in on migrations? Is documentations right? It should works as expected/describe in docs?
If I'm doing it wrong, what is the strategy to work with migrations to run with existing and new on databases?
Dotnet Core version: 1.1.
EFCore version: 1.1.2.
Thanks in advance.
You need a baseline migration for the existing database. In EF 6 you used the -IgnoreChanges flag, but that doesn't exist in Core right now. See here.
You can accomplish the same thing in EF Core by commenting out all the Up() code and applying that migration. This will create the __MigrationHistory table and insert a record denoting it has been applied.
Subsequent migrations will be applied to both and if you need to create a new database you are covered.
Related
I've been following a tutorial to create a database by having a context class, and running the following commands:
dotnet ef migrations add InitialMigration
dotnet ef database update
This did initially work for me, and the expected database was created. Since then I have deleted the migration file and ran the process again, the update command seems to run fine, but when I check the database, the tables have not been created.
If I look in the migration file, I can see that it looks fine and appears to have the correct code in it to create the tables I want.
I don't think I've actually changed anything, so why has the update command stopped working as it did before?
deleting you migration file didn't delete your database
so your database must be still existed however , if your create a new migration with the same name and update your database this will not effect you database since the migration is have been applied to your database
try to delete your database manually from SQL explorer then try update-database
Remove all migrations from your Migration folder in dot net project.
Create a new migration from CLI or from wherever you are making. (dotnet-ef migrations add..)
In the .cs file of this new migration file, comment all the CREATE TABLES commands for existing tables i.e. migration.Create...this one (These will be in the Up method of your migration file)
Just keep CREATE commands for only required tables.
Apply the update.(dotnet-ef database update)
Will work like a charm.
I have the following.
An Entity Framework model that maps against a SQLSERVER database. This has production data, but there is no __MigrationHistory table. I need to keep the data.
A new updated model including new tables, columns etc.
I would like to add migrations so that model changes can be easily managed. I would like to support both MigrateDatabaseToLatestVersion by creating all default tables, as well as being able to apply migration #2 patches on the current data structure.
I have followed Microsofts tutorial "Code First Migrations with an existing database" but this gives me the problem of the initial -ignoreChanges resulting in not being able to create the model from scratch. I need to be able to both recreate it as well as add migrations on the existing database without migration history. This since the -ignoreChanges on the initial migration gives me an empty up(), and the second migration script will only contain code for the patched tables/columns. If I don't ignore changes then the framework will try to create tables that already exist.
I was considering to not ignore changes on the initial migration and then do some kind of "CREATE TABLE IF NOT EXISTS" for all existing tables, but that seems impossible.
I bet I'm missing something right out in the open. What is it?
not tested but it should do:
use old model to create a _MigrationHistory table
copy/paste (select/insert or any etl method) the _MigrationHistory in the production database
update the model to new one
create a new migration
push the migration to the db.
DO ALL THIS FIRST IN A TEST ENVIRONMENT !
I'm developing a windows application which uses SQL Server Database. I have different versions of this application and they have different database structure, so I need to migrate database to the latest version on application start. I want to compare the database structure with the application model, then do alter, create or drop commands.
Also I want to use EF Code-First ORM, after some search I've figured it out that there are some useful commands and configs in code first. But the problem is, as I know, all of them drop the existing database and create a new one so the data will be lost while I need the data.
I used these lines in my application start function:
var migrator = new DbMigrator(new Configuration());
migrator.Update();
But after execution this line I will get this exception:
There is already an object named 'SomeTable' in the database.
I know that, it's right and there is that table but in structure is changed! How can I compare the structure and do the rest?
That's not how migrations work. You need a migration for every version of your database so EF can check the __MigrationHistory table and see if it has been applied. If your initializer is set to MigrateDatabaseToLatestVersion your database won't be recreated on model changes.
You could try to recreate the history: roll back to your oldest database, add a migration, add 2nd oldest version changes, create a 2nd migration, etc.
Another option is to add a migration for where you are now, generate a script (update-database -Script) then comment out the stuff that exists in each deployed database before applying it.
Yet another option would be to use the VS Schema compare utility against each database and your current database to get the changes over. Then apply a baseline migration to each (add-migration Initial -IgnoreChanges).
Now moving forward you can generate a series of migrations and your code should work as expected.
I am working with doctrine:migrations:diff in order to prepare database evolutions.
This command creates files into app/DoctrineMigrations
Thoses files contains sql commands in order to upgrade or downgrade database scructure.
I want to store those sql commands into the database itself. In fact, i have several instances of databases. If sql commands are store into files, it is a big problem.
I have read somewhere that DoctrineMigrations bundle can create a table called "migration_versions", but i do not manage to find where i have read this...
I cannot really understand what you're trying to do.
Migrations are used when your code needs altered database structure. For example, a new table or a new column. These new requirements for a table or column comes from your newly written code, so it's only natural to place the migrations also as a code in your repository.
How and when would migrations even get to your database? How would you guarantee that migration is executed before the code changes, which use that new structure?
Generally, migrations are used in this way:
You develop your code, add new features, change existing ones. Your code needs changes to database.
You generate doctrine migration class, which contains needed SQL statements for your current database to get to the needed state.
You alter the class adding any more required SQL statements. For example, UPDATE statements to migrate your data, not only the structure.
You execute migration locally.
You test your code with database changes. If you need more changes, you either add new migration, or execute migration down, delete it and regenerate it. Never change the migration class, as you'll loose what's supposed to be in the database and what's not.
You commit your migration together with code that uses it.
Then comes the deployment part:
- For each server, upload the code, clear and warm-up cache, run other installation scripts. Then run migrations. And only then switch to the new code.
This way your database is always in-sync with current code in the server that uses that database.
migration_versions database table is created automatically by doctrine migrations. It holds only the version numbers of migration classes - it's used for keeping track which migrations were already run and which was not.
This way when you run doctrine:migrations:migrate all not-yet-ran migrations are executed. This allows to migrate few commits at once, have several migrations in a commit etc.
We're using Doctrine Migrations to keep the application DB in sync across versions. The app will be installed each time we get a new customer meaning a new DB for each installation.
Now, the new DB will have all DB changes in the migrations file in place but will try to execute the migration files as they are not registered in the migrations table.
What's the best way to handle this situation?
Just after fresh install to fill current schema use this commands:
Create new empty chema of current version
./bin/console doctrine:schema:create
Fill out the migration records with the current version (without actually run the migrations - schema already has current version after first command)
./bin/console doctrine:migrations:version --add --all
This command adds records of the migrations and doctrine:migrations:status will show you that there is no migrations need for the current verions.
Thats all!
As mentioned in my comment, I've successfully created a blank database schema just by using Doctrine migrations. I believe it's necessary to create the empty database first (php app/console doctrine:database:create) and then run the migrations task.
The only potential issue I can think of is that any base data that your app requires to function will either need to be in the migrations files or will need to be inserted separately.
As an aside, running the all the migrations in one go has picked up a couple of small errors that I'd missed when just executing one at a time.
I think you can pick the very first migration class, copy it and rename with just one second before.
So, if your first class is 2016060712284351 you should create a new class called 2016060712284350. This way it is executed just before the real migrations.
In this newly created class you setup your database creating all needed tables. This way, when you run migrations the first thing is done is to create the database with all the tables and then the real migrations are run.
Anyway I'm not sure this is the real way to proceed.
Migrations are needed to update the database schema, but if you are creating a new database for each user, each of the new users will have the new schema as per entities mapping. So a migration is not needed.
You need to run migration only for OLD USERS' DATABASES, am I right?