see on GitHub

Indexing Related Documents

To extend indexing capabilities and simplify many scenarios, we have introduced the possibility to index related documents. For start, lets consider a simple Customer - Invoice scenario where you want to lookup for an Invoice by Customer Name.

public class Invoice
{
	public string Id { get; set; }

	public string CustomerId { get; set; }
}

public class Customer
{
	public string Id { get; set; }

	public string Name { get; set; }
}

Without this feature, the index that had to be created would be a fairly complex multiple map-reduce index and this is why the LoadDocument function was introduced.

public class SampleIndex : AbstractIndexCreationTask<Invoice>
{
	public SampleIndex()
	{
		Map = invoices => from invoice in invoices
						  select new
						  {
							  CustomerId = invoice.CustomerId,
							  CustomerName = LoadDocument<Customer>(invoice.CustomerId).Name
						  };
	}
}

Alternative way is to use PutIndex command:

store.DatabaseCommands.PutIndex("SampleIndex", new IndexDefinition
{
	Map = @"from invoice in docs.Invoices
			select new
			{
				CustomerId = invoice.CustomerId,
				CustomerName = LoadDocument(invoice.CustomerId).Name
			}"
});

Now we will be able to search for invoices using Customer Name as a parameter.

Our next scenario will show us that indexing more complex relationships is also trivial. Lets consider a case:

public class Book
{
	public string Id { get; set; }
	
	public string Name { get; set; }
}

public class Author
{
	public string Id { get; set; }

	public string Name { get; set; }

	public IList<string> BookIds { get; set; }
}

Now to create an index with Author Name and list of Book Names we need to create it as follows:

public class AnotherIndex : AbstractIndexCreationTask<Author>
{
	public AnotherIndex()
	{
		Map = authors => from author in authors
						 select new
							 {
								 Name = author.Name,
								 Books = author.BookIds.Select(x => LoadDocument<Book>(x).Name)
							 };
	}
}

or

store.DatabaseCommands.PutIndex("AnotherIndex", new IndexDefinition
{
	Map = @"from author in docs.Authors
			select new
			{
				Name = author.Name,
				Books = author.BookIds.Select(x => LoadDocument(x).Id)
			}"
});

Note

Indexes will be updated automatically when related documents will change.

Note

Using LoadDocument adds a loaded document to tracking list. This may cause very expensive calculations to occur especially when multiple documents are tracking the same document.