3662521 - The $COUNT query is not supported

• OData $counts fails with error : The $COUNT query is not supported
  
  
• Example:
  
  /sap/opu/odata/sap/API_MRP_MATERIALS_SRV_01/SupplyDemandItems/$count
  
  results error:
  
  <error xmlns="http://schemas.microsoft.com/ado/2007/08/dataservices/metadata">
  <code>SY/530</code>
  <message xml:lang="en">The $COUNT query is not supported</message>
  <innererror>
  <application>
  <component_id>PP-MRP</component_id>
  <service_namespace>/SAP/</service_namespace>
  <service_id>API_MRP_MATERIALS_SRV_01</service_id>
  
  code call stack:
  
  LOG_MESSAGE    /IWBEP/CL_MGW_MSG_CONTAINER===CP
  /IWBEP/IF_MESSAGE_CONTAINER~ADD_MESSAGE_TEXT_ONLY    /IWBEP/CL_MGW_MSG_CONTAINER===CP
  SUPPLYDEMANDITEM_GET_ENTITYSET    CL_API_MRP_MATERIAL_01_DPC_EXTCP
  /IWBEP/IF_MGW_APPL_SRV_RUNTIME~GET_ENTITYSET    CL_API_MRP_MATERIAL_01_DPC====CP
  /IWBEP/IF_MGW_CORE_SRV_RUNTIME~READ_ENTITYSET    /IWBEP/CL_MGW_ABS_DATA========CP
  /IWBEP/IF_MGW_CORE_SRV_RUNTIME~READ_ENTITYSET    /IWBEP/CL_MGW_PUSH_ABS_DATA===CP
  /IWBEP/IF_MGW_CORE_SRV_RUNTIME~READ_ENTITYSET    /IWBEP/CL_MGW_RT_DEF_BADI=====CP
  GET_ENTITY_SET    /IWBEP/CL_MGW_LOCAL_HANDLER===CP
  GET_ENTITY_SET    /IWBEP/CL_MGW_REMOTE_HANDLER==CP
  PROCESS_REQUEST_INT    /IWBEP/CL_MGW_REMOTE_HANDLER==CP
  PROCESS_REQUEST    /IWBEP/CL_MGW_REMOTE_HANDLER==CP
  /IWBEP/FM_MGW_HANDLE_REQUEST    /IWBEP/SAPLFGR_MGW_CLIENT_IF
  /IWBEP/FM_MGW_HANDLE_REQUEST    /IWBEP/SAPLFGR_MGW_CLIENT_IF
  REMOTE_FUNCTION_CALL    SAPMSSY1
  %_RFC_START    SAPMSSY1

SAP Gateway (OData)

$COUNT, /iwbep/cx_mgw_busi_exception, add_message_text_only, has_count( ) , KBA , OPU-GW-COR , Framework , Problem