Hierarchical group by

[Bernd]

Hello all.

The following LINQ statement tells me:

"Execution of 'System.Linq.Enumerable:GroupBy(IEnumerable`1,Func`2)' on the database server side currently not implemented. This occured from g1.GroupBy(o => o.SequenceNumber)"

1.var ops = _db.Operations.Where(o => !filteredStates.Contains(o.ProcessingStatus) && o.CalendarEvents.Count == 0 && o.WorkOrder.QuantityToProduce - o.QuantityConfirmed > 0)
2.    .GroupBy(o => new { o.WorkOrderId }).Select(g1 => new {
3.        g1.Key,
4.        Operations = g1.GroupBy(o => o.SequenceNumber).Select(g2 => g2)
5.    }).ToList();

Any ideas how to work around such a situation?

Kind regards

Bernd

[Viktor Zhivkov]

Hello Bernd,

I believe you can safely split the query into database and in-memory parts while keeping the same behavior and performance. Adding an extra .ToList() call after the first .GroupBy() should do the job:

1.var ops = _db.Operations.Where(o => !filteredStates.Contains(o.ProcessingStatus) && o.CalendarEvents.Count == 0 && o.WorkOrder.QuantityToProduce - o.QuantityConfirmed > 0)
2.    .GroupBy(o => new { o.WorkOrderId })
3.    .ToList();
4.var groupedOps = ops.Select(g1 => new {
5.        g1.Key,
6.        Operations = g1.GroupBy(o => o.SequenceNumber).Select(g2 => g2)
7.    }).ToList();

If you can not apply this work around in your particular scenario, please let us know and give us the details that are preventing you from utilizing the outlined approach

Regards,
Viktor Zhivkov
Telerik

 

[Bernd]

Hello Viktor.

That did the trick. Thank you.

Regards

Bernd