title: Perform sort on field that's not primary index
body: <p>Error:</p>
  
  <pre><code>No index exists for this sort, try indexing by the sort fields.
  </code></pre>
  
  <p>I've tried creating indexes on <code>anotherValue</code>, <code>_id+anotherValue</code>, but no difference.</p>
  
  <p>This is my query:</p>
  
  <pre><code>{
    "selector": {
      "_id": { "$gt": null },
      "$or": [
            { "_id": "10" },
            { "value": "10", "anotherValue": "1234" }]
    },
    "sort": [{"anotherValue": "desc"}]
  }
  </code></pre>
  
  <p>Indexes setup:</p>
  
  <pre><code>Your available Indexes:
  special: _id
  </code></pre>