Boosting

Another great feature that Lucene engine provides and RavenDB leverages is called boosting. This feature gives user the ability to manually tune the relevance level of matching documents when performing a query.

From the index perspective we can associate with an index entry a boosting factor and the higher value it has, the more relevant term will be. To do this we must use Boost extension method from Raven.Client.Linq.Indexing namespace.

To illustrate it better, let's jump straight into the example

public class User
{
	public string FirstName { get; set; }

	public string LastName { get; set; }
}

To perform a query that will return users that either FirstName or LastName is equal to Bob and to promote users (move them to the top of the results) that FirstName matches the phrase, we must first create an index with boosted entry.

public class Users_ByName : AbstractIndexCreationTask<User>
{
	public Users_ByName()
	{
		this.Map = users => from user in users
							select new
								{
									FirstName = user.FirstName.Boost(10),
									LastName = user.LastName
								};
	}
}

Next step is to perform a query against that index.

session.Query<User, Users_ByName>()
	   .Where(x => x.FirstName == "Bob" || x.LastName == "Bob")
	   .ToList();

Boosting is also available when using Search method. You can read more about it here.