6.10 Query Error Handling
In response to a query request, the SData provider MUST return one of the following HTTP status codes:
| Code | Description |
|---|---|
| 200 OK | Query was successful. Response contains a valid <feed> |
| 304 Not Modified | Query was successful. Response is identical to what the consumer has in its cache. Response payload is empty. |
| 400 Bad Request | Generic status for consumer side error. Client MUST modify the request before resubmitting. |
| 401 Unauthorized | Request requires user authentication. See Authentication section for details. |
| 403 Forbidden | Consumer is not authorized to read the requested feed. |
| 404 Not Found | One of the elements specified in the URL does not exist. For example, application name, contract name or resource kind. See note below. |
| 500 Internal Server Error | Serious provider error. Client SHOULD NOT retry the request. |
| 501 Not Implemented | URL is valid but provider does not implement it. See Query on Intermediate URL section. |
| 503 Service Unavailable | Transient provider error. Client MAY retry the request. The provider SHOULD include a Retry-After header in its response to indicate when the consumer MAY retry the request. |
If the query executes successfully but does not select any resources, it MUST return a success code: 200 with an empty feed (or 304 if caching applies). This is not an error and it would be incorrect to return a 404 status in this case.
When the service returns a 4xx or a 5xx status code, it SHOULD include an <sdata:diagnoses> payload with details about the error in its response. See Error Payload section for details.
When the service returns a 200 status code, it MAY include one or more <sdata:diagnosis> in the feed or in individual entries. In this case, the diagnosis elements MUST only be warnings or information, not errors.
SData providers MUST return errors as described above.