GroupBy executes on the client side

The current version of EF Core disregards GroupBy.

Problem

We normally use the LINQ GroupBy method to group records by some common characteristic, probably with the goal of doing aggregations. In most LINQ implementations, this generates a SQL GROUPBY, which is what we want, but, in Entity Framework Core 1.0, this translation is silently ignored, and grouping is instead done on the client-side, after retrieving all records. The problem is, this may bring a lot of records, causing severe performance and memory problems.

Imagine, for example, that you have thousands of products distributed in four colors: blue, red, green, and yellow. You might want to run this query:

var productsGrouped = (from p in context.Products 
groupby p.Color into g 
select new { Color = g.Key, Count = g.Count() })
    .ToDictionary(x => x.Color, x => x.Count);

What will happen is, Entity Framework will bring all the thousands of products into the client application and perform...