title: Is it possible to make a Solr query span several documents grouped by a common field value?
body: <p>Is it possible to do a search across several documents in a Solr index that share a common field value and have Solr treat that as one document?</p>
  
  <p>Let's say for example I upload each chapter of a book into Solr as a separate document, but they share a common field, <code>book</code> which is the title of the book.</p>
  
  <pre><code>&lt;doc&gt;
    &lt;field name="id"&gt;book1_chap01&lt;/field&gt;
    &lt;field name="book"&gt;book1&lt;/field&gt;
    &lt;field name="text"&gt;The proof is in the pudding.&lt;/field&gt;
  &lt;/doc&gt;
  &lt;doc&gt;
    &lt;field name="id"&gt;book1_chap02&lt;/field&gt;
    &lt;field name="book"&gt;book1&lt;/field&gt;
    &lt;field name="text"&gt;The concept is different than the reality.&lt;/field&gt;
  &lt;/doc&gt;
  </code></pre>
  
  <p>If you search now for <code>proof AND concept</code> it would return nothing, because the words occur in separate documents.</p>
  
  <p>I would like a search like <code>proof AND concept</code> to be performed over all documents that share the common book value "book1" as if they were one document.</p>
  
  <p>Is such a thing possible in Solr?</p>