ctx.blogs.ExecuteUpdate(s => s.SetProperty(b => b.SomeJsonDocument.Foo, b => "foo");

Things get interesting when there are multiple updates inside the same JSON document:

ctx.blogs.ExecuteUpdate(s => s
    .SetProperty(b => b.SomeJsonDocument.Foo, b => "foo")
    .SetProperty(b => b.SomeJsonDocument.Bar, b => "bar");

We could apply the same logic we're discussing for SaveChanges:

1. Do "least-common-denominator" to find the smallest branch containing all the properties to be updated.
2. As a further optimization, nest multiple invocations (e.g. of JSON_MODIFY for SQL Server) to update the two properties; but we need to investigate and benchmark to know to what extent that makes sense and when.