Poor performance when loading entity with large string property using Entity Framework

Question

Given an entity and a DbContext like the following:

public class Entity
{
    public int Id {get;set;}
    public string LargeString {get;set;}
}

public class MyDbContext : DbContext
{
    public DbSet<Entity> Entities {get;set;}
}

And an entity stored in the database with Id 42 and LargeString containing some two megabytes of XML. The following takes half a minute or so, and occasionally gives OutOfMemoryException:

using (var dbContext = new MyDbContext())
{
    var entity = await dbContext.Entities.SingleAsync(e => e.Id == 42);
}

At the same time, the following Dapper query executes in miliseconds:

using (var dbContext = new MyDbContext())
{
    var entity = await dbContext.Database.Connection
        .Query<Entity>("SELECT Id, LargeString FROM Entities WHERE Id = 42")
        .SingleAsync();
}

Is it possible to somehow hint Entity Framework that the LargeString property could be this large (in a way that would make Entity Framework perform acceptable in this scenario).

try `dbContext.Entities.AsNoTracking().Single(e => e.Id == 42);` if that fixes let me know — undefined, Nov 08 '16 at 20:41
The `AsNoTracking()` does not improve performance significantly. However, a colleague of mine pointed out that our production code that this question simplifies is asynchronous, and that might be relevant for performance, so I updated the example code to reflect this. — Robert Jørgensgaard Engdahl, Nov 09 '16 at 09:47

score 5 · Accepted Answer · edited May 23 '17 at 12:13

5

I had the same issue yesterday. What I did find out is that async operations with Entity Framework is broken or at least very slow. Try using the same operations synchronously:

using (var dbContext = new MyDbContext())
{
    var entity = dbContext.Entities.Single(e => e.Id == 42);
}

Also read the post by rducom here: https://stackoverflow.com/a/28619983/7108481

edited May 23 '17 at 12:13

Community

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answered Nov 09 '16 at 10:05

Jogge

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Poor performance when loading entity with large string property using Entity Framework

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