title: does a unique index give the same benefit as a basic index
body: <p>I'm constructing my migration in and would like two fields to have an index for performance reasons as several joins are performed on these fields. </p>
  
  <p><a href="http://laravel.com/docs/schema#adding-indexes" rel="nofollow">http://laravel.com/docs/schema#adding-indexes</a></p>
  
  <p>These two fields also happen to be unique together so I need a unique constraints index. In the laravel doc the unique and the index are both under the same section 'indexes' so I was wondering if they are essentially the same in the background. Would a unique index automatically give me the index performance benefit?</p>
  
  <p>If I set a <strong>unique constraints index</strong> </p>
  
  <pre><code>$table-&gt;unique(array('object_type', 'object_id')); 
  </code></pre>
  
  <p><strong>question 1)</strong> will this achieve the same benefits as a <strong>basic index</strong></p>
  
  <pre><code>$table-&gt;index('object_type');
  $table-&gt;index('object_id');
  </code></pre>
  
  <p><strong>question 2:</strong> do I need to set the engine type as InnoDB when I set these types of index?</p>
  
  <pre><code>Schema::create('my_table', function (Blueprint $table) {
    $table-&gt;increments('id');
  
    $table-&gt;string('object_type');
    $table-&gt;unsignedInteger('object_id');
  
    $table-&gt;engine = 'InnoDB';
    $table-&gt;unique(array('object_type', 'object_id'));
  });
  </code></pre>