var results = session.Query<DocumentLog>()
                    .Where(x => x.action_type_cd == activity &&
                                x.action_date >= DateTime.Now.Date.AddDays(daysBack))
                            .GroupBy(ts => new {  ADate= ts.action_date.Date,ts.doc_id,ts.user_id,ts.action_type_cd })
                .Select(g => new { g.Key.doc_id, g.Key.user_id, g.Key.action_type_cd, g.Key.ADate, Cnt = g.Count() });