efcore: EF Core 1.0 RC2: async queries so much slower than sync

One of the features that I have missed in EF6 it was the possibility to use includes with raw quieries. This is possible with EF Core, something like this:

await myDbContext.MyDbSet.FromSql("Select * from Mytable")
.Include(x=> x.Property1.Property2.Property6)
.Include(x=> x.Property3.Property4.Property5)
.Include(x=> x.Property7.Property7)
.ToListAsync();

The problem is that this query it is very slow, about 5 minutes. When I use LinQ the time is slower, much slower, but in my case I wanted to use raw quieries because I want to use the hints of Sql Server to block some rows.

I am using Express Profiler to get the query that EF Core send to Sql Server, and if I run this query in Sql Server Management Studio, it takes just 3 seconds to complete. So the problem it seems to be in EF Core.

Also, with Express Profiler I see that the query makes 370000 reads that takes 310000 seconds (about 5 minutes). But I don’t understand this because in SSMS takes 3 seconds this query.

I have tried this query:

await myDbContext.MyDbSet.FromSql("Select * from Mytable")
.ToListAsync();

This takes 3 seconds, but if I try this one:

await myDbContext.MyDbSet.FromSql("Select * from Mytable")
.Include(x=> x.Property1.Property2)
.ToListAsync();

It takes 77 seconds.

With EF6, the same query with all the includes takes 3 secods, and I am using a IQueryable that has to create the t-sql query. I have expected that EF Core would have a better performace than EF6, at least not so bad. The problem with EF6 is that if I want to use the hints of Sql Server I have to do two queries, one with the raw sql to block the rows and another query, with LinQ, to bring the entities to the dbContext and the includes.

Anyway, if I use the same query with LinQ with EF Core, it takes a bit more, about 4 seconds, so it has worse performace.

Really I don’t know if I am doing something wrong or EF Core with the includes has worse performance than EF6. And with raw query with includes it is very bad.

I guess that EF Core has problem populating the navigation properties, because really the t-sql that send to the database is very fast, the total time it is very big.

Thanks.