In this session we will explore several modeling scenarios from my own experience that can easily be achieved using RavenDB, but difficult (if not nearly impossible) to build using a classic relational database. The focus will be on helping those accustomed to SQL Server or other relational databases learn good document modeling skills by example, with a summary of document modeling guidelines at the end.

1. Modeling Tricks My Relational
Database Never Taught Me
David Boike
@DavidBoike
make-awesome.com

2. About Me
• Principal Consultant, ILM Professional Services
• NServiceBus Champion
• Author of Learning NServiceBus
• Husband, father, geek,
amateur beer brewer
• @DavidBoike
• www.make-awesome.com

3. SQL Server

4. SQL Server

5. SQL Server
• SQL first appeared – 1974
– Hard drive price: $185/MB, $189,000/GB
• Microsoft SQL Server 1.0 – 1989
– Hard drive price: $7.48/MB, $7,659/GB
• Current Version: SQL 2012
– November 2013: 0.004¢/MB, 4.096¢/GB
http://www.jcmit.com/diskprice.htm

7. Entity Framework

9. SQL Server

10. RavenDB

11. What is RavenDB?
• Fully transactional document database
• Dead simple API
Store(object entity) Delete<T>(T entity)
Load<T>(string id) Query<T>()
• Smart LINQ-powered client library
• Safe by default
• Powerful indexes
• Replication/sharding
• Fraction of SQL Server’s cost
• Fraction of SQL Server’s requirements

12. RavenDB

13. Document Modeling

14. Bad Document Modeling

15. Take the red pill…

16. Inheritance
Oh boy, Com Sci 101 again!

17. Inheritance: Flat

18. Cliché Polymorphism Examples
• Animals (cat, dog, horse)
• Cars (sedan, truck, minivan, SUV)
– More broadly, machines (bike, motorcycle, car)
• Shapes (circle, rectangle, square)

19. Inheritance: Table per Class
Ale
BeerId
AleProp1
AleProp2
Beer
BeerId
Type
Name
ABV
IBU
Lager
BeerId
LagerProp1
LagerProp2
Stout
BeerId
StoutProp1
StoutProp2

20. Inheritance: Table per Top-Level Class

21. Inheritance: Extended Attributes
AttributeNames:
foo:S:0:11:intVal:S:11:2:
AttributeValues:
Hello World42
Deserialized:
foo=“Hello World”
bar=“42”

22. Inheritance: XML Attributes

23. Raven Inheritance
public class BeerListModel
{
public string Id { get; set; }
public List<BeerModel> Beers
{ get; set; }
public BeerListModel()
{
Beers = new List<BeerModel>();
}
}
public abstract class BeerModel
{
public string Name { get; set; }
public decimal ABV { get; set; }
public int IBU { get; set; }
}
public class AleModel : BeerModel
{
public string AleProp1 { get; set; }
public string AleProp2 { get; set; }
}
public class LagerModel : BeerModel
{
public string LagerProp1 { get; set; }
public string LagerProp2 { get; set; }
}
public class StoutModel : BeerModel
{
public string StoutProp1 { get; set; }
public string StoutProp2 { get; set; }
}

24. Raven Inheritance

25. Inheritance: Lessons
• Inheritance/Polymorphism in SQL Server sucks
• In RavenDB, it’s no big deal
• Key: With RavenDB we can model things just
like they exist in real life.

26. Hierarchy

27. SQL Hierarchy
SELECT *
FROM Category
WHERE SiteId = @SiteId
AND ParentId = @ParentId

28. SQL Hierarchy
SELECT *
FROM Category
WHERE SiteId = @SiteId

29. Raven Hierarchy #1
public class CategoryTree
{
// Sites/42/Categories
public string Id { get; set; }
public List<Category> RootCategories { get; set; }
public CategoryTree()
{
RootCategories = new List<Category>();
}
}

30. Raven Hierarchy #1
public class Category
{
public string CategoryId { get; set; }
public string Name { get; set; }
// Other Stuff
public List<Category> ChildCategories { get; set; }
public Category()
{
ChildCategories = new List<Category>();
}
}

31. Raven Hierarchy #1

32. Raven Hierarchy #2
public class Category
{
public string Id { get; set; }
public string Name { get; set; }
// Other Stuff
}
public class CategoryTree
{
public string Id { get; set; }
public List<CategoryRef> RootCategories { get; set; }
}
public class CategoryRef
{
public string CategoryId { get; set; }
public List<CategoryRef> ChildCategories { get; set; }
}
// Don't forget default constructors!

33. Raven Hierarchy #2

34. Loading Hierarchy
• Method 1
– One document, just load it
• Method 2
– Multiple Documents
– Normally to load within collections
• .Include("RootCategories,CategoryId")
• Does not work recursively
• Works fine for one level

35. Loading Hierarchy
var tree = RavenSession
.Load<CategoryTree>("Sites/42/CategoryTree");
// Recursively build list of ids needed
string[] ids = RecurseOnYourOwnTime(tree); // ;-)
var cats = RavenSession
.Load<Category>(ids)
.ToDictionary(doc => doc.Id);

36. Hierarchy: Lessons
• Model by Units of Change and Transactional
Boundaries
– Guided our choice of hierarchy implementation
– Think about actors in your use cases
• Always initialize collections and child objects
– Nobody likes a NullReferenceException
• We can have global “singleton” documents for
configuration
– Site/Configuration, Site/Categories, etc.
– Great candidates for Aggressive Caching

37. Duplication
You want me to do what?

38. Wordpress ERD

39. Wordpress ERD
Comments
Comment
Meta
Options
Posts
PostMeta
Term
Relationships
Users
UserMeta
Term
Taxonomy
Links
Terms

40. Copy a Post
• 3 tables involved
– wp_posts
– wp_postmeta (17 types)
– wp_term_relationships
• More if we want to copy comments
– wp_comments
– wp_commentmeta

41. Copy a Post
• Fairly simple example
– New row in Posts
• Store new PostId
– New rows in PostMeta w/ PostId
– New rows in TermRelationships w/ PostId
• What if we had to copy a table related to
TermRelationships?
• What if an object graph spans dozens of tables?
• What if PostMeta contains hidden ids linking to other
tables?
• P.S. Revisions are stored as additional
records in Posts!

42. Raven Post Model Example
public class WordPressPost
{
public string Id { get; set; }
public string AuthorId { get; set; }
public DateTimeOffset PostDate { get; set; }
public string Contents { get; set; }
public string Title { get; set; }
public string Excerpt { get; set; }
public PostStatus Status { get; set; }
// etc.
public List<string> Categories { get; set; }
public List<string> Tags { get; set; }
public List<string> Series { get; set; }
public List<string> RelatedPostIds { get; set; }
public List<PostLink> Links { get; set; }
public List<PostMedia> Media { get; set; }
// Comments?...
}

43. Options for Comments
1. Add to WordPressPost :
public List<PostComment> Comments { get; set; }
2. Document per comment
3. Separate document for comments
• WordPressPosts/1
• WordPressPosts/1/comments
4. Capped documents
• WordPressPosts/1
• WordPressPosts/1/comments/1
• WordPressPosts/1/comments/2
• WordPressPosts/1/comments/3

44. Capped Documents
Bounded Contexts Unbounded Contexts
Posts/1 Posts/1
Posts/1/Comments
Posts/1/
Comments/3
Posts/1/
Comments/2
Posts/1/
Comments/1

45. How to duplicate?
// Global.asax / App_Start config
Mapper.Initialize(cfg =>
{
cfg.CreateMap<BlogPost, BlogPost>()
.ForMember(p => p.Id,
opts => opts.Ignore());
});
Can also decorate model’s Id property with
IgnoreMapAttribute but this leaks a dependency to
AutoMapper in your models.

46. How to duplicate?
BlogPost post =
RavenSession.Load<BlogPost>("BlogPosts/1");
BlogPost dupe = Mapper.Map<BlogPost>(post);
// dupe.Id == null
RavenSession.Store(dupe);
// dupe.Id == "BlogPosts/2"

47. Why duplicate?
• User Duplicate function (duh)
• Auditing/History
– Posts/1/History/yyyyMMddHHmmss
– Consider Versioning bundle for auditing EVERY
document modification
• Preview
– Posts/1/Preview/ecbe7b49c3de4c8394880bdd81eeae97
• Use Expiration Bundle
• Complex Edit/Publish/Cancel
– Posts/1/Edit/davidboike
• Use Expiration Bundle

48. Duplication: Lessons
• Thinking about duplication can help to identify
units of change, but can’t get us all the way
• Make use of semantic IDs
• Duplicating data enables many advanced
scenarios
• Think about possible document growth
• Break down large documents within one unit
of change into slimmer documents

49. NServiceBus Saga Storage
Hey remember that book I
mentioned?

50. NServiceBus/Sagas 101
• NServiceBus
– Framework for creating distributed systems
– Transactional message handlers w/ auto-retry
– Publish/Subscribe
• NServiceBus Sagas
– Correlated message handlers with shared state
– Transactional state stored between messages
– Similar in concept to ASP.NET Session State

51. Saga Storage Interface
public interface ISagaPersister
{
T Get<T>(Guid sagaId);
T Get<T>(string property, object value);
void Save(IContainSagaData saga);
void Update(IContainSagaData saga);
void Complete(IContainSagaData saga);
}
public interface IContainSagaData
{
Guid Id { get; set; }
string Originator { get; set; }
string OriginalMessageId { get; set; }
}

52. Saga Storage History
• NServiceBus 2.0
– SQL Storage via Fluent NHibernate
• It sucked
– Built my own based on XmlSerializer
• That also sucked, just not as much
• NServiceBus 3.0
– RavenDB Saga Persister became default
– Villagers rejoiced!

53. Fluent NHibernate
public class MySagaData : IContainSagaData
{
public virtual int MessagesReceived { get; set; }
// Don't touch! NServiceBus uses these internally!
public virtual Guid Id { get; set; }
public virtual string Originator { get; set; }
public virtual string OriginalMessageId { get; set; }
}
MySagaData
Id
Originator
OriginalMessageId
MessagesReceived

54. Fluent NHibernate
public class MySagaData : IContainSagaData
{
public virtual int MessagesReceived { get; set; }
// Don't touch! NServiceBus uses these internally!
public virtual Guid Id { get; set; }
public virtual string Originator { get; set; }
public virtual string OriginalMessageId { get; set; }
}
MySagaData
Id
Originator
OriginalMessageId
MessagesReceived

55. Fluent NHibernate
public class MySagaData : BaseSagaData
{
public virtual int MessagesReceived { get; set; }
}
public abstract class BaseSagaData : IContainSagaData
{
public virtual Guid Id { get; set; }
public virtual string Originator { get; set; }
public virtual string OriginalMessageId { get; set; }
}
MySagaData
Id
MessagesReceived
BaseSagaData
Id
Originator
OriginalMessageId

56. Fluent NHibernate
public class MySagaData : IContainSagaData
{
public virtual List<string> MessageTypesReceived { get; set; }
// Don't touch!
public virtual Guid Id { get; set; }
public virtual string Originator { get; set; }
public virtual string OriginalMessageId { get; set; }
}

57. Fluent NHibernate
public class MySagaData : IContainSagaData
{
public virtual List<string> MessageTypesReceived { get; set; }
// Don't touch!
public virtual Guid Id { get; set; }
public virtual string Originator { get; set; }
public virtual string OriginalMessageId { get; set; }
}

58. Fluent NHibernate
public class MySagaData : IContainSagaData
{
public virtual List<ReceivedMessage> MessageTypesReceived { get; set; }
// Don't touch!
public virtual Guid Id { get; set; }
public virtual string Originator { get; set; }
public virtual string OriginalMessageId { get; set; }
}
public class ReceivedMessage
{
public virtual Guid Id { get; set; }
public virtual string MessageTypeReceived { get; set; }
}
MySagaData
Id
Originator
OriginalMessageId
ReceivedMessage
Id
MySagaDataId
MessageTypeReceived

59. Raven Saga Persistence
public class MySagaData : ContainSagaData
{
public List<string> MessageTypesReceived { get; set; }
}
-OR-
public class MySagaData : ContainSagaData
{
public HashSet<Type> MessageTypesReceived { get; set; }
}

60. Back to ISagaPersister
public interface ISagaPersister
{
T Get<T>(Guid sagaId);
T Get<T>(string property, object value);
void Save(IContainSagaData saga);
void Update(IContainSagaData saga);
void Complete(IContainSagaData saga);
}
Need to be able to load a saga by any identifiable
property that matches on the incoming message
and saga data.

61. More Real-Life Saga
Shipping Saga:
• Waits for OrderAccepted + OrderBilled events
• Publishes OrderShipped event
public class ShippingData : ContainSagaData
{
[Unique]
public long OrderId { get; set; }
public List<string> MessageTypesReceived { get; set; }
}
UniqueAttribute
• NHibernate persister would create a unique index on the column
• RavenDB indexes are asynchronous and NOT consistent
– Consistency only guaranteed on Store/Load by ID

62. Pointer Documents
// PubSub.Shipping.ShippingData/OrderId/{GUID-1}
{
"SagaId": "{GUID-2}",
"UniqueValue": 12345,
"SagaDocId": “ShippingData/{GUID-2}"
}
// ShippingData/{GUID-2}
{
"OrderId": 12345,
"Originator": "PubSub.Sales@ILM-LION",
"OriginalMessageId": "{GUID-3}"
}

63. OpenID/OAuth
• Login with multiple 3rd-party identities also requires
pointer document modeling
• OpenID identity URLs make for horrible document IDs
– Use the SHA1 hash of the login provider and login
identifier in the document ID instead.
• Easy way with MVC5
– RavenDB.AspNet.Identity NuGet package
– https://github.com/ILMServices/RavenDB.AspNet.Identity
– At least look at the source and make fun of the author
(That’s me)

64. RavenDB.AspNet.Identity
{ // ApplicationUsers/DavidBoike (Some boring properties removed)
"UserName": "DavidBoike",
"Logins": [
{
"LoginProvider": "Google",
"ProviderKey": "https://www.google.com/accounts/o8/id?id=AItOawnt..."
}
]
}
{ // IdentityUserLogins/95c8f50aa725d62af9c7e397ca3a89889dd76514
"UserId": "ApplicationUsers/DavidBoike",
"Provider": "Google",
"ProviderKey": "https://www.google.com/accounts/o8/id?id=AItOawnt..."
}

65. NServiceBus: Lessons
• Document databases are ideal for storing
random objects with little friction
• Unique constraints must be treated specially
to ensure consistency
– Custom pointer documents
– Unique Constraints bundle for more generic
functionality (though I prefer not to overuse it)
• Use RavenDB.AspNet.Identity for OpenID
– Better yet send me a pull request!

66. Final Thoughts
Document modeling is not the same as SQL.
If you try to make it so, you will fail.
So don’t be that guy.

67. Final Thoughts
Above all else, think about how and why data
changes.
– Units of Change
– Transactional Boundaries
– Everything else is window dressing

68. Final Thoughts
Like relational modeling, document modeling is
a skill that is acquired through experience
– Model things like you would in the real world
– Don’t be afraid of trying and failing
– Create a /FakeData/Create action in your site to
bootstrap your database to make this easy
– Especially in the early stages of an application,
experiment often and regenerate when needed

69. Questions?
@DavidBoike
make-awesome.com