Entity Framework Poor COUNT Performance

Question

We are experiencing very poor performance using Entity Framework 5.0 with MySql Connector 6.6.6.0 for count based queries. Our data structure looks like:

Table: P         


        

Answer 1

Testing with EF 6

db.Users.Count(u => u.LastName == "xyz")

and

db.Users.Where(u=>u.LastName=="xyz").Count()

produce identical sql queries.

SELECT 
[GroupBy1].[A1] AS [C1]
FROM ( SELECT 
    COUNT(1) AS [A1]
    FROM [dbo].[Users] AS [Extent1]
    WHERE N'xyz' = [Extent1].[LastName]
)  AS [GroupBy1]

Answer 2

Try

var count = entities.Post.Where(p => 
       p.SiteID == 1 && p.CreatedDate != null).Query().Count();

http://msdn.microsoft.com/en-us/data/jj574232.aspx

Has this at the bottom of the page:

Using Query to count related entities without loading them

Sometimes it is useful to know how many entities are related to another entity in the database without actually incurring the cost of loading all those entities. The Query method with the LINQ Count method can be used to do this. For example:

using (var context = new BloggingContext()) 
{ 
    var blog = context.Blogs.Find(1); 

    // Count how many posts the blog has  
    var postCount = context.Entry(blog) 
                          .Collection(b => b.Posts) 
                          .Query() 
                          .Count(); 
}