Cosmos: Complex order by support

[smitpatel]

SELECT (c["CustomerID"] || c["City"]) AS A
FROM root c
WHERE (c["Discriminator"] = "Customer")
ORDER BY (c["CustomerID"] || c["City"])

gives

Failed to query documents for collection Customer: {"code":400,"body":"{\"code\":\"BadRequest\",\"message\":\"Message: {\\\"errors\\\":[{\\\"severity\\\":\\\"Error\\\",\\\"message\\\":\\\"Unsupported ORDER BY clause. ORDER BY item expression could not be mapped to a document path.\\\"}]}\\r\\nActivityId: 891abdd0-f420-43ff-a843-bf82687d7ff4, Microsoft.Azure.Documents.Common/2.4.0.0\"}","activityId":"891abdd0-f420-43ff-a843-bf82687d7ff4"}

[divega]

EF Triage: We don't reason about indexes in the database. We produce the SQL you asked for, and if the index doesn't exists, you will get an error from the database engine.