Feature suggestion: Migrations

[code1line]

What do you think about migrations-support?

[msallin]

Hi Michael

Of course migrations support would be great.
I have not much Experience with entity framework, but as fare as I know the EF Migrations mechanismus consists of two parts.

1. MigrationSqlGenerator
   This class must be implemented. It will generate the SQL statements based on the commands. Which means this class needs to know how to tread a CreateTable() which is used in a migration.
2. MigrateDatabaseToLatestVersion<TContext, TMigrationsConfiguration> Class
   Normally you would use this initializer to use migrations. But as the code first stuff is done in a own initializer, this class could not be used. That means a) a own migrations class needs to be written or b) we find out what exactly the MigrateDatabaseToLatestVersionclass does and then just implement the necessary stuff (like create the History Table) so that the functionality of the MigrateDatabaseToLatestVersionclass could be reused.

It seems very complicated to me and may there is another way to do this.

[code1line]

I agree - it would be great, but it does not seem to be an easy task. It may be planned for a future release...

[GaryWolfe]

Migrations would be ideal, as that seems to be how EF is typically presented with Code First.

Is there some documentation on how to use EF with Code First but not with migrations? Everything I find seems to discuss migrations (which requires the above-mentioned sql generator class). When I try running "update-database", it asks for the sql generator. I'm sorry if this isn't the right forum for this question, but how do I use this project and SQLite without migrations?

I have this working as code-first (with migration) in SQL Server, but wanted to try SQLite, as the db is small and SQL Server is overkill.

[msallin]

Hi Gary

1. You can use EF without migrations. Have a look at the Code in this Repo, there is a sample Application.
2. You can not run "update-database" because there is no implementation for the SQL Generator.
3. See 1. Just delete your migrations may be an option, because the Model (Code) should be up to date.

I once tried to dive into EF and find out how the migrations are implemented.
But I was not able to create a own sql generator.

In the (Issue 16)[https://github.com//issues/16] HareIM posted a link with an implementation for such an sql generator. May you can try to use this: https://drive.google.com/file/d/0B-NCqWnMQpBrQjkxMkxnVlRzb00/view?pli=1

[GaryWolfe]

Thanks for the fast response, Marc! I think I can probably live without the migrations with my small project, but the Sql Generator sounds intriguing. I'll have a look at that and the sample code you mention as time permits.

Working on this last night, I kept getting a zero-byte SQLite database generated, so I must be doing something wrong; it did not re-build a freshly seeded db as I would have expected. Since I have been using SQL Server, it seems to hang on to that information somewhere. When I run, it creates a zero byte SQLite db, but then runs off of the SQL Server db! (I've commented-out the connection strings in the web.config for SQL Server, so not sure how it does that!) I like how EF automates things, but I guess it also hides what it's doing. (In other work, I use DB-first, and I think that's best for larger projects. I've had success working with that, so I've been tempted to go that route.) If I continue to be stuck, I'll just start over with a "fresh" project and copy files over, to ensure that it only uses SQLite.

Thanks for clarifying things.

[HarelM]

+1

[tg73]

I've got a working prototype for migrations. It was originally based on the prototype put together by Julio C. Borges in 2013, although significant further work was required. Several migration operations are currently not implemented, notably those ALTER TABLE operations which are not natively supported by SQLite (see https://www.sqlite.org/lang_altertable.html).

The code is not as clean or well-formatted as I'd like for issuing a pull request, so for the time being you can get it here:

https://github.com/zanyants/SQLiteCodeFirst/tree/feature/migrations

To use:

To your migrations Configuration class ctor, add:

SetSqlGenerator( "System.Data.SQLite", new SQLite.CodeFirst.SqliteMigrationSqlGenerator() );

And in your context's OnModelCreating add:

Database.SetInitializer( new System.Data.Entity.MigrateDatabaseToLatestVersion<MyContext, Migrations.Configuration>( true ) );