export multi value with Generic SQL Connecor to a MS SQL Database

Question

Hello dear IdM fellowers,

I am struggling for days now the figure out how to export multiple values through the Generic SQL Connector using MIM2016. I am using only the Sync component without FIM Service or Portal - it is just plain code provisioning.

I am able to import multi value data but it seems to be impossible to export. I have tried it with table/views/stored proc exports but with no success.
The first data row of a multi value entry is exported fine because the foreign key ID is pushed/exported to the database resulting in a correct export. But this works only for the first row because the connector did not populate the foreign key on changes/updates to a multi value data field. Is there any way to force the population/export of a specific field?

this is my database schema

this is how my Anchor and DN are definined in 'Schema 3' (not visible is the anchor of Employee which is EmployeeId)

this is my attribute mapping. I used a rules extension for group Id to be able to export the Group_Id right after provisioning the group.

Here is the respective code to map the Group_Id

 void IMASynchronization.MapAttributesForExport (string FlowRuleName, MVEntry mventry, CSEntry csentry)  
        {  
            switch (FlowRuleName)  
            {  
                case "cd.Group:Group_Id<-mv.group:<object-id>":  
                    csentry["Group_Id"].StringValue = csentry["Id"].StringValue;  
  
                    break;  
                default:  
                    throw new EntryPointNotImplementedException();  
            }  
        }  

This is the provision code in the MV extension

private bool ProvisioningAdGroupToIdmDb(MVEntry mventry, ConnectedMA agent)  
        {  
            bool result = false;  
            string csAnchorName = "GroupName";  
            string mvValueName = "cn";  
  
            try  
            {  
                if (mventry[mvValueName].IsPresent)  
                {  
                    Logging.Log("create new connector on " + agent.Name + " for " + mventry[mvValueName].Value);  
                    var csentry = agent.Connectors.StartNewConnector("Group");  
                    string guid = mventry.ObjectID.ToString();// Guid.NewGuid().ToString();  
                    var dn = agent.CreateDN("CN=" + guid).Concat("OBJECT=Group");  
                    csentry["Id"].StringValue = guid;  
                    //csentry["Group_Id"].StringValue = guid;  
                    csentry.DN = dn;  
                    csentry[csAnchorName].Value = mventry[mvValueName].Value;  
                    csentry.CommitNewConnector();  
                    result = true;  
                }  
                else  
                {  
                    Logging.Log("WARNING: Cannot provision due to missing cn", false);  
                }  
            }  
            catch (Exception e)  
            {  
                Logging.Log($"ERROR: {e.Message}", false);  
            }  
  
            return result;  
        }  

thats my export profile

This is what I see in a SQL trace when there is an update to the members field (multi value, mapped to Members_Id)

exec sp_executesql N'Set xact_abort on  INSERT INTO GROUPMEMBERS  
 ( [Member_Id])   
 VALUES  (@P1) ;  Set xact_abort off ',N'@P1 nvarchar(36)',N'fa191b61-1b3a-48de-b895-0fbb7c3a376e'  

I can think of the reason why the Group_Id ist not exported because it has not changed but without the Group_Id the INSERT into the GroupMembers table is just half of the thruth.

Can anyone give me a hint or a simple demo on how to achive an export? It would be great because I am out of any ideas on how to approach this.
Many thanks!