Finding similar documents

Imagine a situation where you want to show documents similar to those that were returned by Solr. For example, let's assume that we have an e-commerce library, and we want to show users similar books to the ones that they found while using your application. Of course, we can use machine learning and one of the collaborative filtering algorithms, but we can also use Solr for that. This recipe will show you how to do this.

How to do it...

1. Let's start with the following index structure (just add this to your schema.xml file):

   <field name="id" type="string" indexed="true" stored="true" required="true" />
   <field name="name" type="text_general" indexed="true" stored="true" termVectors="true" />

2. Next, let's index the following test data:

   <add>
    <doc>
     <field name="id">1</field>
     <field name="name">Solr Cookbook first edition</field>
    </doc>
    <doc>
     <field name="id">2</field>
     <field name="name"&gt...