Customizing results order using SortOptions

Indexes in RavenDB are lexicographically sorted by default, so all queries return results which are ordered lexicographically. When putting a static index in RavenDB, you can specify custom sorting requirements, to ensure results are sorted the way you want them to.

Native types

Dates are written to the index in a form which preserves lexicography order, and is readable by both human and machine (like so: 2011-04-04T11:28:46.0404749+03:00), so this requires no user intervention, too.

Numerical values, on the other hand, are stored as text and therefore require the user to specify explicitly what is the number type used so a correct sorting mechanism is enforced. This is quite easily done, by declaring the required sorting setup in SortOptions in the index definition:

public class Products_ByUnitsInStock : AbstractIndexCreationTask<Product>
{
	public Products_ByUnitsInStock()
	{
		Map = products => from product in products
						  select new
						  {
							  product.UnitsInStock
						  };

		Sort(x => x.UnitsInStock, SortOptions.Int);
	}
}

The index outlined above will allow sorting by value on the number of units in stock (1, 2, 3, 11, etc) for each Product. If we would specify SortOptions.String, then values would have been sorted lexically (1, 11, 2, 3, etc).

The default SortOptions value is String. Appropriate values available for all numeric types (Byte, Double, Float, Int, Long and Short).

Example

In the following query we are using the OrderBy method in order to indicate that we want to sort on UnitsInStock:

IList<Product> results = session
	.Query<Product>()
	.OrderBy(product => product.UnitsInStock)
	.ToList();

So, by default it will sort on UnitsInStock as it was a string. By specifying Sort(x => x.UnitsInStock, SortOptions.Int) in the index definition, we indicate that the sort order should be in a numerical order.

Collation support

RavenDB supports using collations for documents sorting and indexing. You can setup a specific collation for an index field, so you can sort based of culture specific rules.

The following is an example of an index definition which allows sorting based on the Swedish lexical sorting rules:

public class Products_ByName : AbstractIndexCreationTask<Product>
{
	public Products_ByName()
	{
		Map = products => from product in products
						  select new
						  {
							  product.Name
						  };

		Sort(x => x.Name, SortOptions.String);

		Analyzers.Add(x => x.Name, "Raven.Database.Indexing.Collation.Cultures.SvCollationAnalyzer, Raven.Database");
	}
}

In general, you can sort using Raven.Database.Indexing.Collation.Cultures.<two-letters-culture-name>CollationAnalyzer, and all the cultures supported by the .NET framework are supported.