Rescoring query results

Imagine a situation in which your score calculation is affected by numerous function queries, which makes the score calculation very CPU-intensive. This is not a problem for small result sets, but it is for larger ones. Starting from Solr 4.9, this great search engine gives us the possibility of rerank results. This means that Solr will get some results from our initial query and will apply another query only on those results. The query that is applied modifies the score of the documents. This recipe will show you how this can be done.

How to do it...

Let's say that we have a use case where we want to show the latest books added to our index and boost them on the basis of some additional query. To do this, we will need to take the following steps:

1. Let's start with a simple index structure. Our index will be built of three fields that look as follows (please put the following entries to the schema.xml file):

   <field name="id" type="string" indexed="true" stored="true...