Queries such as the prefix query and the wildcard query—basically, any query that is said to be multiterm—use query rewriting. Elasticsearch does this because of performance reasons. The rewrite process is about changing the original, expensive query to a set of queries that are far less expensive from the Lucene point of view.
The best way to illustrate how the rewrite process is carried out internally is to look at an example and see what terms are used instead of the original query term. Let's suppose that we have the following data in our index:
curl -XPOST 'localhost:9200/library/book/1' -d '{"title": "Solr 4 Cookbook"}' curl -XPOST 'localhost:9200/library/book/2' -d '{"title": "Solr 3.1 Cookbook"}' curl -XPOST 'localhost:9200/library/book/3' -d '{"title": "Mastering Elasticsearch"}'
What we want is to find all the documents that start with the letter s. It's as simple as that; we run the following query against our library index:
curl ...
