Entity Framework and multiple contexts on same database

[hoekki]

Hi everyone,

I stumbled upon what seems to be a bug in devart dotConnect for oracle. I am using entity framework in my application, having currently 2 separate contexts, in separate assemblies. When I create the databases, the first is created without problems, however, the second one crashes. Debugging with DbMonitor led me to the _MigrationHistory table. It seems, dotConnect tries to create the whole table again, which of course fails. Also it fails to register the second context in the _MigrationHistory table, so concerning migrations, the second context is broken. All other tables of the second context are created correctly, however.

I get the following output on the creation of the second context:

Code: Select all

-- Table "__MigrationHistory"
CREATE TABLE "__MigrationHistory" ( 
  "MigrationId" NVARCHAR2(150) NOT NULL,
  "ContextKey" NVARCHAR2(300) NOT NULL,
  "Model" BLOB NOT NULL,
  "ProductVersion" NVARCHAR2(32) NOT NULL,
  CONSTRAINT "PK___MigrationHistory" PRIMARY KEY ("MigrationId", "ContextKey")
)

which fails, as it already exists. With a nice ORA-00955 Exception.
Right after, I get another error, Entity Framework executing the following query:

SELECT
"top"."Id",
"top"."ModelHash"
FROM ( SELECT
"Extent1"."Id",
"Extent1"."ModelHash"
FROM "EdmMetadata" "Extent1"
ORDER BY "Extent1"."Id" DESC
) "top"
WHERE ROWNUM <= 1

If I ignore all these exceptions, The program works well, as all the tables are there. But I also need migrations, and that is hindered by the messed up _MigrationHistory table.

Tried this on a SqlServer, working quite well.

Of course I could use ContextKey to add a prefix for the tables, creating two separate migration history tables, one for each context. But I rather not have to fall back to that workaround, as in oracle, name lengths are already forced to be short as is.

Edit: It works if I disable and delete migrations on both contexts. Now both context share the same MigrationHistory table and everything works fine. Well, except the migrations So this hickup only occurs with multiple contexts AND migrations.


Best regards


PS: using EF 6.1.3, dotConnect 8.5.506

[hoekki]

Edit: I did some more testing. It looks like dotConnect does not support multiple contexts at all.
--- Assembly AssemblyA ---
A.cs

Code: Select all

public class A
{
	public int Id{get;set;}
}

ContextA.cs

Code: Select all

[DbConfigurationType(typeof(MyConfiguration)]
public class ContextA : DbContext
{
	public DbSet<A> As{get;set;}
	protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            base.OnModelCreating(modelBuilder);
            modelBuilder.Configurations.Add(new AMap());
        }
}

AMap.cs

Code: Select all

class AMap : EntityTypeConfiguration<A>
{
	public AMap(
	{
		ToTable("As");
		HasKey(x=>x.Id);
	}
}

--- Assembly AssemblyB ---
B.cs

Code: Select all

public class B
{
	public int Id{get;set;}
}

ContextB.cs

Code: Select all

[DbConfigurationType(typeof(MyConfiguration)]
public class ContextB : DbContext
{
	public DbSet<B> Bs{get;set;}
	protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            base.OnModelCreating(modelBuilder);
            modelBuilder.Configurations.Add(new BMap());
        }
}

BMap.cs

Code: Select all

class BMap : EntityTypeConfiguration<B>
{
	public BMap(
	{
		ToTable("Bs");
		HasKey(x=>x.Id);
	}
}

--- Assembly Configuration ---
MyConfiguration.cs

Code: Select all

public class MyConfiguration : DbConfiguration
{
	public MyConfiguration()
	{
		var _ = typeof (System.Data.Entity.SqlServer.SqlProviderServices);
		var __ = typeof (System.Data.Entity.SqlServerCompact.SqlCeProviderServices);
		SetProviderServices("Devart.Data.Oracle", OracleEntityProviderServices.Instance);
		var conf = OracleEntityProviderConfig.Instance;
		conf.CodeFirstOptions.ColumnTypeCasingConventionCompatibility = true;
		conf.DmlOptions.BatchUpdates.Enabled = true;
		conf.Workarounds.IgnoreSchemaName = true;
		conf.DatabaseScript.Schema.DeleteDatabaseBehaviour = DeleteDatabaseBehaviour.AllSchemaObjects;
		conf.QueryOptions.CaseInsensitiveComparison = true;
		conf.QueryOptions.CaseInsensitiveLike = true;

		SetProviderServices(System.Data.Entity.SqlServer.SqlProviderServices.ProviderInvariantName,
			System.Data.Entity.SqlServer.SqlProviderServices.Instance);

		SetProviderServices(System.Data.Entity.SqlServerCompact.SqlCeProviderServices.ProviderInvariantName,
			System.Data.Entity.SqlServerCompact.SqlCeProviderServices.Instance);
	}
}

If you compile this and create the databases in a test, initiation of the second context always fails on oracle, however runs without errors on SqlServer and SqlCe. You'll get the ORA-00955 Exception on __MigrationHistory, as I mentioned above.

Please have a look into this.

Best Regards

[Shalex]

Please send us a small test project with the corresponding DDL/DML script so that we can reproduce a scenario which works with System.Data.SqlClient but fails with Devart.Data.Oracle.

[Shalex]

The bug with creating database objects in the same schema by several EF6 contexts in Code-First approach is fixed in v9.2.162: https://www.devart.com/dotconnect/oracl ... story.html.

JIC
Be aware about the change starting from v9.0: viewtopic.php?t=33571 > "Entity Framework Assembly Name Change".