Entity Framework 6 DBContext with only a subset of all tables

Question

We have a huge database with 770 tables and want to do some performance testing with EF 6.1x.

We want to query only 5 of those 770 tables. Is it possible to create a "light" DBContext with only 5-6 entities/DBSets instead of using the full 770-tables-context?

When we use the full context, a simple query with 4 joins takes 45 seconds. Thats' 44 seconds too long. We are using code-first (reverse engineered).

The problem: When we create such a "light" version of the full context (i.e. 5 tables only), EF complains that all the other entities that are somehow related to these 5 tables have missing keys. We only map the keys, properties, relationships for those 5 tables, but not the rest.

Since the query written in LINQ only queries 5 tables, EF should simply ignore the other 765 tables, but it won't. Why not? LazyLoading=true/false doesn't seem to have any bearing on this.

Note: Obviously one could create a view in the DB that does what we do in code with a LINQ query. The question is can it be done with a "light" DbContext as above.

There's the "light" version of the context:

public class ItemLookupContext : DbContext
{
    static ItemLookupContext()
    {
        Database.SetInitializer<ItemLookupContext>( null );
    }

    public ItemLookupContext()
        : base( "Name=ItemLookupContext" )
    {
        //Configuration.LazyLoadingEnabled = true;
    }

    public DbSet<Identity> Identities { get; set; }
    public DbSet<Item> Items { get; set; }
    public DbSet<Price> Prices { get; set; }
    public DbSet<Department> Departments { get; set; }
    public DbSet<Brand> Brands { get; set; }

    protected override void OnModelCreating( DbModelBuilder modelBuilder )
    {
        modelBuilder.Configurations.Add( new IdentityMap() );
        modelBuilder.Configurations.Add( new ItemMap() );
        modelBuilder.Configurations.Add( new PriceMap() );
        modelBuilder.Configurations.Add( new DepartmentMap() );
        modelBuilder.Configurations.Add( new BrandMap() );

        //ignore certain entitities to speed up loading?
        //does not work
        modelBuilder.Ignore<...>();
        modelBuilder.Ignore<...>();
        modelBuilder.Ignore<...>();
        modelBuilder.Ignore<...>();
        modelBuilder.Ignore<...>();
    }
}

Answer 1

what you trying to something like "Bounded Context" which is one of DDD patterns

So, you can check this article by Julie Lerman, Shrink EF Models with DDD Bounded Contexts