Problem Statement

Search operation with chained referencing is not working after enabling MDM expansion search.

Description

When MDM expansion search is enabled, search operations with chained reference are failing.
Example: http://localhost:8000/AllergyIntolerance?patient.identifier=https://api.loblaw.ca/fhir/NamingSystem/hw-1222%7Cpaaaid1102101

This worked fine before enabling the MDM expansion search. but doesn't work after enabling it. Below is the error message

{
    "resourceType": "OperationOutcome",
    "issue": [
        {
            "severity": "error",
            "code": "processing",
            "diagnostics": "HAPI-2001: Resource NamingSystem/hw-1222|paaaid1102101 is not known"
        }
    ]
}

Cause

Based on the doc and the current MDM expansion implementation, the expansion only supports reference search that contains the reference ID, such as [base]/Observation?patient:mdm=Patient/123.
Consequently, the chained reference search of ?patient.identifier=https://api.loblaw.ca/fhir/NamingSystem/hw-1222%7Cpaaaid1102101 would lead to incorrect parsing of the resource ID.

Fix

Add a check to only allow MDM expansion for non-chained reference search.