title: Laravel - Eloquent "relation" submit query only one time
body: <p>I noticed a strange behaviour using eloquent relation.</p>
  
  <p>I wrote this simple test:</p>
  
  <pre><code>Route::get('/myTest', function () {
      $book = \App\Models\BookModel::findOrFail(7);
  
      $count_start = 1;
      $count_end   = 3;
      while ($count_start &lt;= $count_end) {
          \Log::info('  A');
          $position = $book-&gt;position-&gt;name;
          \Log::info('  B');
          sleep(5);
          $count_start++;
      }    
  });
  </code></pre>
  
  <p>the <strong>Log</strong> reposts:</p>
  
  <pre><code>[2019-07-09 13:40:04] - INFO:   A
  [2019-07-09 13:40:04] - DEBUG:  query: {"sql":"select * from `position` where `position`.`fk_book` = ? limit 1","time":4.66,"bindings":[7]}
  [2019-07-09 13:40:04] - INFO:   B
  [2019-07-09 13:40:09] - INFO:   A
  [2019-07-09 13:40:09] - INFO:   B
  [2019-07-09 13:40:14] - INFO:   A
  [2019-07-09 13:40:14] - INFO:   B
  </code></pre>
  
  <p>The strange behaviour is that the first time the process enter in the <code>while</code>, the query is correctly execute; the second and third times (after 5sec) the query is not executed again and I do not understand why!</p>
  
  <p>Is this normal? Why the relation query is executed only first time?</p>
  
  <p>Thank you.</p>