在效率更高的Linq中，加入或包含

Question

I'm trying to get a collection of objects, and I would like to find out which is more efficient. Right now my query gets 16 results, but we may be working with a dataset of 1000s.

Let's say I'm working with the following models:

public ProjectSubmission()
{
    [Key, DatabaseGenerated(DatabaseGeneratedOption.None)]
    public Guid ProjectSubmissionId { get; set; }

    public System.Guid ProjectId { get; set; }
    [ForeignKey("ProjectId")]
    public virtual Project Project { get; set; }

    public string SubmissionTitle { get; set; }  
}

public Project()
{
    [Key, DatabaseGenerated(DatabaseGeneratedOption.None)]
    public Guid ProjectId { get; set; }

    public string Title { get; set; } 
}

Which will provide me better performance, this:

var subVModel = 
(
    from ps in db.ProjectSubmission
        .Include(s => s.Project)
    where ps.IsActive
        && (filter.ProjectId == Guid.Empty || ps.Project.ProjectId == filter.ProjectId)
        && (filter.SubmissionTitle == string.Empty || ps.SubmissionTitle .Contains(filter.SubmissionTitle))
    select ps); 

or:

var subVModel = 
(
    from ps in db.ProjectSubmission
    join p in db.Project on ps.ProjectId equals p.ProjectId
    where ps.IsActive
        && (filter.ProjectId == Guid.Empty || p.ProjectId == filter.ProjectId)
        && (filter.SubmissionTitle == string.Empty || ps.SubmissionTitle .Contains(filter.SubmissionTitle))
    select ps); 

Right now they both result in .032 seconds for 16 records.

Answer 1

There will be no difference is simple case because the Include call generates a join clause to get the data from the included property. On the other hand if you want to select only some of the columns from the included navigation property you will not be able to do it with Include. If you use join you can specify which columns you want to include in the result set.

Answer 2

Although include is more simpler syntax to read , There is no difference in simple cases . But in some cases include cause extra joins(Before EF 6.1). and cause extra time . It's a bug in EF and reported here

Any way it's better to use a EF profiler and monitor your query . Like Entity Framework Profiler , or use Glimpse EF extension