Acumatica GetList error: Optimization cannot be performed.The following fields cause the error: Attributes.AttributeID - acumatica

Question

Developer's version of Acumatica 2020R1 is installed locally. Data for sample tenant MyTenant from training for I-300 were loaded, and WSDL connection established.
DefaultSoapClient is created fine.
However, attempts to export any data by using Getlist cause errors:
using (Default.DefaultSoapClient soapClient =
new Default.DefaultSoapClient())
{
//Sign in to Acumatica ERP
soapClient.Login
(
"Admin",
"*",
"MyTenant",
"Yogifon",
null
);
try
{
//Retrieving the list of customers with contacts
//InitialDataRetrieval.RetrieveListOfCustomers(soapClient);
//Retrieving the list of stock items modified within the past day
// RetrievalOfDelta.ExportStockItems(soapClient);
RetrievalOfDelta.ExportItemClass(soapClient);
}
public static void ExportItemClass(DefaultSoapClient soapClient)
{
Console.WriteLine("Retrieving the list of item classes...");
ItemClass ItemClassToBeFound = new ItemClass
{
ReturnBehavior = ReturnBehavior.All,
};
Entity[] ItemClasses = soapClient.GetList(ItemClassToBeFound);
string lcItemType = "", lcValuationMethod = "";
int lnCustomFieldsCount;
using (StreamWriter file = new StreamWriter("ItemClass.csv"))
{
//Write the values for each item
foreach (ItemClass loItemClass in ItemClasses)
{
file.WriteLine(loItemClass.Note);
}
}
The Acumatica instance was modified by adding a custom field to Stock Items using DAC, and by adding several Attributes to Customer and Stock Items.
Interesting enough, this code used to work until something broke it.
What is wrong here?
Thank you.
Alexander

Answer 1

In the request you have the following line: ReturnBehavior = ReturnBehavior.All
That means that you try to retrieve all linked/detail entities of the object. Unfortunately, some object are not optimized enough to not affect query performance in GetList scenarios.
So, you have to options:
Replace ReturnBehavior=All by explicitly specifying linked/detail entities that you want to retrieve and not include Attributes into the list.
Retrieve StockItem with attributes one by one using Get operation instead of GetList.
P.S. The problem with attributes will most likely be fixed in the next version of API endpoint.
Edit:
Code sample for Get:
public static void ExportItemClass(DefaultSoapClient soapClient)
{
Console.WriteLine("Retrieving the list of item classes...");
ItemClass ItemClassToBeFound = new ItemClass
{
ReturnBehavior = ReturnBehavior.Default //retrieve only default fields (without attributes and other linked/detailed entities)
};
Entity[] ItemClasses = soapClient.GetList(ItemClassToBeFound);
foreach(var entity in ItemClasses)
{
ItemClass itemClass= entity as ItemClass;
ItemClass.ReturnBehavior=ReturnBehavior.All;
// retrieve each ItemClass with all the details/linked entities individually
ItemClass retrievedItemCLass = soapClient.Get(itemClass);
}