Entity Framework Core 2 – DbContext Pools

Entity Framework Core 2 was released on August 14th. It brought new features.

On this article I will explain one of them: DbContext Pools

Normally when a DbContext is injected somewhere by the dependency injection framework, a new instance is created every time. With this, we can have a pool of instances, 128 by default. It is a performance improvement and it is configured like this (console app example):

var serviceProvider = new ServiceCollection()
 .AddDbContextPool<AdventureWorksContext>(options => { //options })
 .AddScoped<IEfQueries, EfQueries>()
 .BuildServiceProvider();

.AddDbContext from Entity Framework Core 1 is still implemeted in Entity Framework Core 2.

What kind of improvment to expect ?

Let’s build a Query and let’s see the improvment by using 2 instances of the queries service intantiated by injection dependency system:

public Orders GetOrderById(int id)
{
   return _context.WorkOrders.Select(
                             x => new Orders
                             {
                                Id = x.WorkOrderId,
                                ProductName = x.Product.Name,
                                Quantity = x.OrderQty,
                                Date = x.DueDate
                             }).FirstOrDefault(x => x.Id == id);
}

// Using AddDbContext 
var efqueriesService1 = serviceProvider.GetService<IEfQueries>();
efqueriesService1.GetOrders();
var efqueriesService2 = serviceProvider.GetService<IEfQueries>();
efqueriesService2.GetOrders();

// Using AddDbContextPool
var efqueriesService1 = serviceProvider.GetService<IEfQueries>();
efqueriesService1.GetOrders();
var efqueriesService2 = serviceProvider.GetService<IEfQueries>();
efqueriesService2.GetOrders();

I executed this serie of execution 20 times and I measured the execution (using Stopwatch object) this:

With AddDbContext:

• Instance 1: 23 to 29 ms (instantiation + execution)
• Instance 2: 7 to 9 ms (instantiation + execution)

With AddDbContextPool:

• Instance 1: 17 to 21 ms (instantiation + execution)
• Instance 2: 5 to 7 ms (instantiation + execution)

It looks a bit more performant! 😉