title: Solr join for multiple collection with each collection have multiple shards
body: <p>I have <em>two collections</em>: </p>
  
  <ul>
  <li><p><code>CollectionOne</code> with two shards <code>(shard1, shard2)</code> have <code>id</code>, <code>name</code>, and <code>Address</code> fields</p></li>
  <li><p><code>CollectionTwo</code> with shards <code>(shard1,shard2)</code> have <code>c_id</code>, <code>code</code>, and <code>State</code> fields.</p></li>
  </ul>
  
  <p>I want the result from two collection on <code>id=c_id</code> base using <code>join</code>.</p>
  
  <p>Please provide me full help! I am using <code>Solr</code> version 6.1.0.</p>