Code-First .NET and MongoDB

1. The Ubiquitous Blog Example Philly ALT.NET User Group 2010-11-16 John C. Zablocki Development Lead, MagazineRadar Adjunct, Fairfield University Code-First .NET and MongoDB

2. Agenda • MongoDB Basic Concepts • MongoDB Shell • NoRM • MongoDB C# Driver • MongoDB Design Considerations • In Depth: Meringue • Case Study: RateMySnippet • Questions?

3. MongoDB Concepts • Schema-less documents stored in collections • Documents are stored as BSON (Binary JSON) • JavaScript used to query and manipulate documents and collections • Each document in a collection has a unique BSON ObjectId field named _id • Collections belong to a database

4. Installing MongoDB on Windows • Download the binaries from mongodb.org • Extract to Program Files directory (or wherever) • Create a directory c:\data\db • Run mongod.exe from the command line with the --install switch • See http://bit.ly/aed1RW for some gotchas • To run the daemon without installing, simply run mongod.exe without arguments • Run mongo.exe to verify the daemon is running

5. A funny thing happened on the way to Philadelphia... MongoDB and .NET

6. MongoDB - Shell • The MongoDB interactive JavaScript shell (mongo.exe) is a command line utility for working with MongoDB servers • Allows for CRUD operations on collections • May be used for basic administration • Creating indexes • Cloning databases • Also useful as a test-bed while building apps

7. MongoDB - Shell /*Connect to a server:port/database (defaults are localhost:27017/test ):*/ mongo.exelocalhost:27017/AltNetGroup //Switch database: use CodeCamp //View collections in a database: showcollections //create an index on Name field db.Posts.ensureIndex({ Name : 1 }); //copy one database to another db.copyDatabase("CodeCamp", "AltNetGroup")

8. //create a document varpost = { Title: "On Installing MongoDB as a Service on Windows" } //insert a document, if the collection doesn't exist it's created db.Posts.insert(post); //verify that the document was created db.Posts.find(); //write a query to find a post with a valid title varquery = { Title: { $ne: null} } //use that query to find the post varpost = db.Posts.findOne(query); //this line will actually set the content after pressing enter post.Content = "When installing MongoDB as a service on Windows..." MongoDB - Shell

9. //update the content to include an author using collection update method db.Posts.update( { Title : "On Installing MongoDB as a Service on Windows" }, { Author : "John Zablocki" } ) //check that the post was updated db.Posts.findOne() //where'd my document go? updates are in place, replacing entire documents! //need to use the $set operator to update partial documents - let's start over //first remove the new document. Notice how remove takes a func as an argument. //find and findOne also accept functions as arguments db.Posts.remove(function (e) { returnthis.Author == "John Zablocki" }) //rerun the first statements up to but not including the db.Posts.update(... db.Posts.update({ Title: "On Installing MongoDB as a Service on Windows" }, { $set: { Author: "John Zablocki" } }) //verify that the update worked db.Posts.findOne() MongoDB - Shell

10. //add a tag to the post db.Posts.update({ Title: "On Installing MongoDB as a Service on Windows" }, { $push: { Tags: "mongodb" } }) //look for that tag db.Posts.findOne() //add two more tags db.Posts.update({ Title: "On Installing MongoDB as a Service on Windows" }, { $pushAll: { Tags: ["windows", "nosql"] } }) //add another post db.Posts.insert( { Author : "John Zablocki", Title : "On MapReduce in MongoDB", Tags: ["mongodb", "nosql"] }) //verify that last insert worked db.Posts.findOne(function (e) { returnthis.Title.indexOf("MapReduce") != -1; }) MongoDB - Shell

11. //add a "like" counter to the post. The booleans arguments tell update //not to insert if the document doesn't exist and to update all documents, //not just one respectively db.Posts.update({ Author: "John Zablocki" }, { $set: { Likes: 0} }, false, true) //increment the likes counter for the mapreduce article db.Posts.update({ Title: /mapreduce/i }, { $inc: { Likes: 1} }) //check that the counter was incremented db.Posts.findOne({ Title: /mapreduce/i }).Likes MongoDB - Shell

12. MongoDB – Shell /* Create the map function This function creates a view that looks like{ “mvc”, [1, 1] }, { “norm”, [1] }*/ varmap = function() { if (!this.Tags) { return; } for (varindexinthis.Tags) { emit(this.Tags[index], 1); } };

13. MongoDB – Shell MapReduce /* Create the reduce function conceptually, reduce gets called like: reduce("mvc", [1, 1]); reduce("norm", [1] /* varreduce = function(key, vals) { varcount = 0; for (varindexinvals) { count += vals[index]; } returncount; };

14. MongoDB – Shell MapReduce /* Run the mapreduce command on the Posts collection using the map and reduce functions defined above store the results in a collection named Tags */ varresult = db.runCommand( { mapreduce : "Posts", map : map, reduce : reduce, out : "Tags" }); db.Tags.find()

15. Something Completely Different

16. NoRM

17. NoRM • Developed by Andrew Theken among others • Active community with reliable support • I received help even as I prepared this slide! • Support for typed and untyped collections, MapReduce, Property Mapping, LINQ, Expando, nearly all CRUD operations • Will eventually sit on top of the 10gen officially supported driver

18. NoRM – The Basics //Connections managed with IDisposable pattern //Connect to test database on localhost using (IMongomongo=Mongo.Create("mongodb://localhost/test")) { Console.WriteLine(mongo.Database.DatabaseName); } //Mongo instance has MongoDatabase property /*MongoDatabase has GetCollection<T> methods for accessing MongoCollection instances*/ //CRUD operations performed on collections

19. NoRM - CRUD //Class properties map to document structure publicclassArtist { //ObjectId property mapped to _id field in document publicObjectIdId { get; set; } publicstringName { get; set; } //IList property will be mapped to JavaScript Array privateIList<string>_albums=newList<string>(0); publicIList<string>Albums { get { return_albums ; } set { _albums =value; } } }

20. NoRM - CRUD varartist=newArtist() { Name="The Decembrists" }; //Inserting a document into a typed collectionmongo.Database.GetCollection<Artist>("Artists").Insert(artist); //Updating (replacing) a document in a typed collection artist.Name="The Decemberists"; mongo.Database.GetCollection<Artist>("Artists").Save(artist); //Updating a nested collection mongo.Database.GetCollection<Artist>("Artists").UpdateOne( new { Name="The Decemberists"}, new { Albums=M.Push("Picaresque") } );

21. NoRM - CRUD //Find all documents in a typed collection varartists=mongo.GetCollection<Artist>("Artists").Find(); Console.WriteLine(artists.FirstOrDefault().Name); //Query with a document spec varartist=mongo.GetCollection<Artist>("Artists") .FindOne( new { Name="The Decemberists" }); Console.WriteLine(artist.Albums.Count); //Count the documents in a collection longcount=mongo.GetCollection<Artist>("Artists").Count(); Console.WriteLine(count);

22. NoRM - MapReduce //Add a Tags collection added to Artist class privateIList<string>_tags; publicIList<string>Tags { get { return_tags; } set { _tags=value; } } //Add some tags – use Set not PushAll, since Tags was nullmongo.Database.GetCollection<Artist>("Artists").UpdateOne( new { Name="The Decemberists" }, new { Tags=M.Set(newList<string>() { "Alternative", "Folk Rock }) });

23. NoRM - MapReduce //Create map and reduce functons stringmap=@"function() { if (! this.Tags ) { return; } for (index in this.Tags) { emit(this.Tags[index], 1); } }"; stringreduce=@"function(previous, current) { var count = 0; for (index in current) { count += current[index]; } return count; }";

24. NoRM - MapReduce //MapReduce class is responsible for calling mapreduce command MapReducemr=mongo.Database.CreateMapReduce(); //Represents the document passed to the //db.runCommand in the shell example MapReduceOptionsoptions=newMapReduceOptions("Artists") { Map=map, Reduce=reduce, OutputCollectionName="Tags" }; MapReduceResponseresponse=mr.Execute(options); varcollection=mongo.Database.GetCollection<Tag>("Tags"); Console.WriteLine(collection.Count());

25. NoRM - LINQ //LINQ provider exposed via AsQueryable method of MongoCollection varartists=mongo.Database.GetCollection<Artist>("Artists") .AsQueryable(); //Find items in typed collection varartistsWithDecInName=fromainmongo.Database.GetCollection<Artist>().AsQueryable() wherea.Name.Contains("Dec") selecta; Console.WriteLine("First containing Dec in name: "+artistsWithDecInName.First().Name);

26. NoRM - LINQ //Find artists without pulling back nested collections //Note use of Regex name search varartistsWithoutAlbums= fromainmongo.Database.GetCollection<Artist>().AsQueryable() whereRegex.IsMatch(a.Name, "ber", RegexOptions.IgnoreCase) selectnew { Name=a.Name }; Console.WriteLine(artistsWithoutAlbums.First().Name); //Find artists with a given tag varartistsWithFolkRockTag=mongo.Database.GetCollection<Artist>("Artists") .AsQueryable().Where(a=>a.Tags.Any(s=>s=="Folk Rock")); Console.WriteLine(artistsWithFolkRockTag.First().Name);

27. MongoDB C# Driver • 10gen developed and supported • Consists of two primary components, a BSON serializer and the MongoDB driver • Support for typed and untyped collections, MapReduce, and all CRUD operations • Currently lacking a LINQ provider • Released about two weeks ago as version 0.7!

28. MongoDB C# Driver – The Basics • privatestaticMongoDatabase_mongoDatabase=null; • staticProgram() { • //MongoConnectioSettings used to create connection strings • MongoConnectionSettingssettings=newMongoConnectionSettings(); • settings.Address=newMongoServerAddress("localhost", 27017); • //MongoServer manages access to MongoDatabase • MongoServermongoServer=newMongoServer(settings); • //MongoDatabase used to access MongoCollection instances • _mongoDatabase=mongoServer.GetDatabase("AltNet"); • }

29. MongoDB C# Driver - CRUD • varartist=newArtist() { Name="The Decembrists" }; • //Inserting a document into a typed collection_mongoDatabase.GetCollection<Artist>(COLLECTION).Insert(artist); • //Updating (replacing) a document in a typed collectionartist.Name="The Decemberists"; • _mongoDatabase.GetCollection<Artist>(COLLECTION).Save(artist); • //Updating a nested collection_mongoDatabase.GetCollection<Artist>(COLLECTION).Update( • Query.EQ("Name", "The Decemberists"),newBsonDocument("$pushAll",newBsonDocument("Albums", newBsonArray() { "Castaways and Cutouts", "Picaresque", "Hazards of Love", "The Crane Wife" })) • );

30. MongoDB C# Driver - CRUD • //Find all documents in a typed collection • varartists=_mongoDatabase.GetCollection<Artist>(COLLECTION).FindAll(); • Console.WriteLine("Artist name: "+artists.FirstOrDefault().Name); • //Query with a document specvarartist=_mongoDatabase.GetCollection<Artist>(COLLECTION).FindOne(newBsonDocument { { "Name", "The Decemberists" } }); • Console.WriteLine("Album count: "+artist.Albums.Count); • //Count the documents in a collectionlongcount=_mongoDatabase.GetCollection<Artist>(COLLECTION).Count();Console.WriteLine("Document count: "+count);

31. MongoDB C# Driver - CRUD • varartists=_mongoDatabase.GetCollection<Artist>(COLLECTION); • //Find items in typed collection • varartistsStartingWithThe=artists.Find(Query.Matches("Name", newRegex("the", RegexOptions.IgnoreCase))); • Console.WriteLine(artistsStartingWithThe.First().Name); • //Find artists without pulling back nested collectionsvarartistsWithDecInTheName=artists.Find(Query.Matches("Name", "Dec")).SetFields("Name"); • Console.WriteLine(artistsWithDecInTheName.First().Name); • ////Find artists with a given tag • varartistsWithIndieTag=artists.Find(Query.In("Tags", "Indie")); • Console.WriteLine( artistsWithIndieTag.First().Name);

32. MongoDB C# Driver - MapReduce • //Add some tags • _mongoDatabase.GetCollection<Artist>(COLLECTION).Update(Query.EQ("Name", "The Decemberists"),newBsonDocument("$pushAll",newBsonDocument("Tags", newBsonArray() { "Folk rock", "Indie" })) ); • varartist=newArtist() { Name="Sunny Day Real Estate",Albums=newList<string>() { "How it Feels to be Something On", "Diary" },Tags=newList<string>() { "Indie", "Emo" }}; • _mongoDatabase.GetCollection<Artist>(COLLECTION).Save(artist);

33. MongoDB C# Driver - MapReduce • _mongoDatabase.GetCollection<Artist>(COLLECTION).Save(artist); • //Create map and reduce functonsBsonJavaScriptmap=@"function() {...}"; • BsonJavaScriptreduce=@"function(previous, current) { ... }"; • varresult=_mongoDatabase.GetCollection<Artist>(COLLECTION).MapReduce(map, reduce, MapReduceOptions.SetKeepTemp(true).SetOutput("Tags"));

34. In Depth: Meringue

35. Design Considerations • Your object graph is your data model • Don't be afraid to store data redundantly • Your graph might be redundant • Not everything has to fit in 1 document • Don't be afraid to store aggregate statistics with a document.

36. Object Graph as Data Model • Generally speaking, most MongoDB drivers will serialize an object graph as a single document • The relationships of your classes creates an implied schema! • Migrating this schema is not trivial if you are trying to deserialize properties that did not or no longer exist • Consider use cases carefully to avoid inefficiently structured documents • Projection queries will be your friend

37. Redundant Data is OK • Optimize documents for quick reads and writes • Your application layer will have to maintain referential integrity! • If every time you access a Post document, you need some of an Author document's data, store that data with Post • Design simple classes for this redundant data for reusability (see AuthorInfo in Meringue)

38. Do Not Stuff it In 1 Document • Nothaving formal relationships does not mean throwing away relationships • Consider a user and his or her logged actions • The user would likely have a User class/doc with properties for name, email, etc. • User actions are generally write heavy and read out of band. • Don't clutter user documents - create a separate collection for user actions

39. Don't Be Afraid of Extra Data • The schema-less nature of documents makes it easy to store meta data about that document – particularly aggregate data • Consider a blog post with a rating feature • Each rating would be stored as a nested document of the post • Rather than compute vote totals and averages real time, simply add these properties to the document and update on writes

40. Case Study: RateMySnippet.com

41. Final Thoughts Eat food. Not too much. Mostly plants. - Michael Pollan

42. Final Thoughts Write Code. Not too much. Mostly C#. - John Zablocki

43. The Meringue Stack • ASP.NET MVC • MVCContrib • MongoDB • Mongo C# Driver • Spring.NET • Recoil • AutoMapper

44. Links • http://dllHell.net - my blog • http://www.CodeVoyeur.com - my code • http://www.linkedin.com/in/johnzablocki • http://twitter.com/codevoyeur • http://mongodb.org - Official MongoDB site • http://bitbucket.org/johnzablocki/meringue • http://bitbucket.org/johnzablocki/codevoyeur-samples