title: Retrieving row count from QSqlQuery, but got -1
body: <p>I'm trying to get the row count of a QSqlQuery, the database driver is qsqlite</p>
  
  <pre><code>bool Database::runSQL(QSqlQueryModel *model, const QString &amp; q)
  {
      Q_ASSERT (model);
  
      model-&gt;setQuery(QSqlQuery(q, my_db));
      rowCount = model-&gt;query().size();
      return my_db.lastError().isValid();
  }
  </code></pre>
  
  <p>The query here is a select query, but I still get <code>-1</code>;</p>
  
  <p>If I use <code>model-&gt;rowCount()</code> I get only ones that got displayed, e.g 256, but select count(*) returns 120k results. </p>
  
  <p>What's wrong about it?</p>