b__ 0(Int32 index, Int32[] offsets, IDataReader reader) in c:\CI\b\rofx\932\Data Abstract for .NET\Source\RemObjects.DataAbstract\Linq\RemoteTable.pas:line 293
at RemObjects.DataAbstract.Linq.LinqRemoteDataAdapter.FetchData(TableRequestInfo[] tableRequest, String[] tableNames, Action`3 fillMethod) in c:\CI\b\rofx\932\Data Abstract for .NET\Source\RemObjects.DataAbstract\Linq\LinqRemoteDataAdapter.pas:line 431
at RemObjects.DataAbstract.Linq.RemoteTable`1.Execute(Expression expression, DataParameter[] parameters) in c:\CI\b\rofx\932\Data Abstract for .NET\Source\RemObjects.DataAbstract\Linq\RemoteTable.pas:line 296
at RemObjects.DataAbstract.Linq.RemoteTableQuery`1.GetEnumerator() in c:\CI\b\rofx\932\Data Abstract for .NET\Source\RemObjects.DataAbstract\Linq\RemoteTableQuery.pas:line 74
at System.Collections.Generic.List`1.AddEnumerable(IEnumerable`1 enumerable)
at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
(...)
```
The project is a .NET Core 2.1 project, using the NetStandard assemblies. Is there something wrong with the LINQ statement? If I change it to an inner join, it works fine.
Thanks,
Arturo.
---
### Author:  [@arturomonge](https://talk.remobjects.com/u/arturomonge)
#### Post date: [May 5, 2019, 8:04pm UTC](https://talk.remobjects.com/t/error-must-be-reducible-node-when-executing-left-join-with-linqdataadapter-netstandard-2-0/19345/2 "2019-05-05T20:04:21Z")
I tried the following variations, which result in the same exact query generated (the query line), but also the same error when executed (the .ToList() line):
```
var query = from e in emailMessages
where (e.MessageId == messageId)
join n in emailNotifications on e.Email_Message_ID equals n.Email_Message_ID into n1
from n2 in n1.DefaultIfEmpty()
select new { Email = e, Notifications = n2 };
var result = query.ToList();
```
and
```
var companyQuery = from e in emailMessages
where (e.MessageId == messageId)
from n in emailNotifications
.Where(notification => notification.Email_Message_ID == e.Email_Message_ID)
.DefaultIfEmpty()
select new { Email = e, Notifications = n };
var result = query.ToList();
```
So it seems to be something in DA’s LINQ processor.
Thanks,
Arturo.
---
### Author:  [@RemObjectsSoftware](https://talk.remobjects.com/u/RemObjectsSoftware)
#### Post date: [May 6, 2019, 10:13am UTC](https://talk.remobjects.com/t/error-must-be-reducible-node-when-executing-left-join-with-linqdataadapter-netstandard-2-0/19345/3 "2019-05-06T10:13:09Z")
Thanks, logged as bugs://82541
---
### Author:  [@antonk](https://talk.remobjects.com/u/antonk)
#### Post date: [May 6, 2019, 10:19am UTC](https://talk.remobjects.com/t/error-must-be-reducible-node-when-executing-left-join-with-linqdataadapter-netstandard-2-0/19345/4 "2019-05-06T10:19:44Z")
Well, this construction is not supported by DA LINQ (even in full .NET). Columns of the linked table have to be explicitly listed in the resulting **Select** to allow the query processor to do its job.
In other words this query will fail:
```
var query = from o in orders
join od in orderDetails on o.Id equals od.OrderId into oj
from od in oj.DefaultIfEmpty()
select new { Order = o, Details = od };
```
While this one does work:
```
var query = from o in orders
join od in orderDetails on o.Id equals od.OrderId into oj
from od in oj.DefaultIfEmpty()
select new {Order = o, Details = new OrderDetails {Id = od.Id, OrderId = od.OrderId}};
```
I’ve logged an issue, however due to the insane complexity of the DA LINQ internals I cannot promise any ETA to simplifying this (ie to allow the 1st query to work as well). Tbh at this moment I am not even sure if that is possible at all.
---
### Author:  [@arturomonge](https://talk.remobjects.com/u/arturomonge)
#### Post date: [May 7, 2019, 8:18pm UTC](https://talk.remobjects.com/t/error-must-be-reducible-node-when-executing-left-join-with-linqdataadapter-netstandard-2-0/19345/5 "2019-05-07T20:18:38Z")
Thanks, no problem. I can use the suggested workaround when I need to do a left outer join.
Arturo.