RavenDB using filter with group by - linq

Question

I have a Transaction entity.
I can make group by by (CustomerCode, CustomerName) then select CustomerCode and Total(Amount).
It is easy. But When I Want to filter AtCreated. I have An Error.
Unhandled exception. Raven.Client.Exceptions.InvalidQueryException: Raven.Client.Exceptions.InvalidQueryException: Field 'AtCreated' isn't neither an aggregation operation nor part of the group by key
Query: from Transactions group by CustomerCode, CustomerName where AtCreated >= $p0 select CustomerCode, count() as Total
Parameters: {"p0":"2019-01-01T00:00:00.0000000"}
public class Transactions
{
public string Id { get; set; }
public long TransId { get; set; }
public DateTime AtCreated { get; set; }
public string CustomerCode { get; set; }
public string CustomerName { get; set; }
public string City { get; set; }
public double Amount { get; set; }
public string GXF { get; set; }
}
var transactList = session.Query<Transactions>()
.Where(a=>a.AtCreated >= new DateTime(2019,01,01))
.GroupBy(a => new {a.CustomerCode, a.CustomerName})
.Select(a => new {a.Key.CustomerCode, Total = a.Count()})
.ToList();
How can I Grouping filtered data?
Thank You.

Answer 1

Create a Map-Reduce Index and then query on it.
https://ravendb.net/docs/article-page/4.2/csharp/indexes/map-reduce-indexes
For example, in this example, you can query on 'Category' field because it was indexed (meaning it was part of the Map-Reduce index definition)
See short demo examples in:
https://demo.ravendb.net/