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

public class Employees_ByFirstAndLastName : AbstractIndexCreationTask<Employee>
{
	public Employees_ByFirstAndLastName()
	{
		Map =
			employees =>
			from employee in employees
			select new
			{
				FirstName = employee.FirstName.Boost(10),
				LastName = employee.LastName
			};
	}
}

store
	.DatabaseCommands
	.PutIndex(
		"Employees/ByFirstAndLastName",
		new IndexDefinition
		{
			Map = @"from employee in docs.Employees
				select new
				{
					FirstName = employee.FirstName.Boost(10),
					LastName = employee.LastName
				}"
		});

Next step is to perform a query against that index:

// employees with 'FirstName' equal to 'Bob'
// will be higher in results
// than the ones with 'LastName' match
IList<Employee> results = session
	.Query<Employee, Employees_ByFirstAndLastName>()
	.Where(x => x.FirstName == "Bob" || x.LastName == "Bob")
	.ToList();

Remarks