Imagine that you have many big XML files that hold information about the books that are stored on library shelves. There is not much data, just a unique identifier, the name of the book and the author. One day your boss comes to you and says: "Hey, we want to facet and sort on the basis of book author". You can change your XML and add two fields, but why do that, when you can use Solr to do that for you? Well, Solr won't modify your data, but can copy the data from one field to another. This recipe will show you how to do that.
In order to achieve what we want, we need the contents of the author field to be present in the fields named author, author_facet, and author_sort.
Let's assume that our data looks like the following code:
<add> <doc> <field name="id">1</field> <field name="name">Solr Cookbook</field> <field name="author">John Kowalsky</field> </doc> <doc>...