Query Explanation

Some Sapi-nt endpoints support query explanation, which enables you to see the serialized query that Sapi-nt would issue to the data source for a given request. This feature is only available when the application is configured to enable it.

To obtain a query explanation for a request, append /explain to the request path.

For example, to explain the query for the following request:

/station?_view=mini&_limit=1

Use the following Explain API request:

/station/explain?_view=mini&_limit=1

When Sapi-nt is explains the query successfully, it returns a 200 OK response whose body is the raw string serialization of the query, in the relevant syntax (typically SPARQL). For example:

PREFIX  ...

SELECT  ?id ?label ?type
WHERE
  { { SELECT  ?id
      WHERE
        { ?id  rdf:type  metro:UndergroundStation
          FILTER EXISTS {  }
        }
      LIMIT   1
    }
    OPTIONAL
      {   { ?id  rdfs:label  ?label}
        UNION
          { ?id  rdf:type  ?type}}
  }

Sapi-nt may fail to explain the query for one of the following reasons:

The request is invalid (for example, a request parameter has an invalid value).
The requested endpoint is configured to not support query explanation.
The requested endpoint would perform a type of query that is not serializable.

In these cases, it returns a 400 Bad Request response.

Note - If Sapi-nt accepts the original request but returns a 404 Not Found to the explain request, infer that the Explain API is not enabled.