title: Scala Slick. Wrong pagination \w Postgres
body: <p>I'm trying to make simple pagination using Slick with Postgres, but it does not
  work as expected.</p>
  
  <pre class="lang-scala prettyprint-override"><code>// Table 
  // "users_pkey" PRIMARY KEY, btree (id)
  // "users_id_idx" btree (id)
  val id: Column[Option[Long]] = column("id", O.PrimaryKey, O.AutoInc, O.DBType(BigSerial))
  
  // Pagination queries
  users.drop(0).take(20).sortBy(_.id.desc).list
  users.drop(20).take(20).sortBy(_.id.desc).list
  </code></pre>
  
  <p>But results are not ordered as expected. Users ordered by <code>id</code> on inside page, e.g. first page will be like <code>40, 35, 34 ... 4, 2</code> and second <code>39, 38, 36, ... 3, 1</code>.</p>