Applied NoSQL in.net

Transcription

1 Applied NoSQL in.net

2 Topics Survey data management world Install mongodb Map C# classes to mongo collections Explore schema design Write queries against mongodb Update records

3 Breaking with tradition is hard Choosing an RDBMS is an axiom of software development When was the last time you considered alternatives to SQL Server or Oracle for your project? Axiom: a statement or proposition that is regarded as being self-evidently true.

4 Why have RDBMSes persisted? They've worked Tool chain support Concurrency / durability Integration DBs DBAs FUD

5 Integration DBs

6 Integration DBs are hard Schemas are complex Are hard to maintain Coordination sucks, is scary Are hard to scale Can be a single point of failure

7 Integration DBs are hard schemas are overly complex

8 Integration DBs are hard coordination is hard (deployment)

9 Integration DBs are hard coordination is hard (development)

10 Integration DBs are hard hard to scale Image credit: johnantoni

11 Integration DBs are hard single point of failure Image credit: PROerocsid

12 Move towards (micro)services The industry is moving away from integration databases This can take the form of SOA: Service oriented architecture Microservices This does not imply NoSQL

13 Move towards (micro)services

14 Move towards (micro)services Services can control their own data stores More schema flexibility Schema evolution More "truth" in code Still need DBAs?

15 Services enable polyglot persistence

16 History of NoSQL June 11th, 2009, San Francisco, USA Johan Oskarsson (from organized a meetup to discuss advances in data storage which were all using distributed databases leveraging clusters. He asked the group for a short term they could use as a hashtag. [1] Eric Evans (not of DDD fame) proposed #NoSQL and it stuck.

17 Michael's NoSQL Definition Database systems which are cluster-friendly and which trade inter-entity relationships for both simplicity and performance.

18 Most popular document db

19 Most popular document db

20 Most wanted

21 MongoDB: Open Source

22 How do you get MongoDB? 1. Download from (not.com!) 2. Run the installer 3. Create a data and log folder 4. Start the server 5. Create a config file (optional) 6. Register as a system service (optional)

23 Config file example systemlog: destination: file path: /mongodb/logs/mongo-service.log logappend: true storage: directoryperdb: true dbpath: /mongodb/data journal: enabled: true processmanagement: fork: true net: bindip: port: setparameter: enablelocalhostauthbypass: false

24 Defining Schemas MongoDB does not have a schema design yet it has an implicit schema Your code is truth C# classes map to MongoDB collections Schema requirements coming (maybe)

25 C# and MongoDB C# classes are mapped to MongoDB collections Excellent control over serialization Top level classes must define an ID field public class Book { public ObjectId Id {get; set;} //... }

26 Getting started with C#: Demo

27 Getting started with C# Creating a Db class is recommended Step 1: Get access to the MongoDatabase public class Db { private readonly IMongoDatabase db; public Db() { var client = new MongoClient(); db = client.getdatabase("bookstore"); } }

28 Getting started with C# Step 2: Create C# class for each collection Id field is required public class Book { public ObjectId Id { get; set; } public string Title { get; set; } public DateTime Published { get; set; } public ObjectId Publisher { get; set; } }

29 Getting started with C# Step 2: Result public class Book // C# { public ObjectId Id { get; set; } public string Title { get; set; } public DateTime Published { get; set; } public ObjectId Publisher { get; set; } } { // JSON / BSON "_id" : ObjectId(" a93bb c12"), "Title" : "Classical Mythology", "Published" : ISODate(" T08:00:00.000Z"), "Publisher" : ObjectId(" f3a93bb a3") }

30 Getting started with C# Step 3: Map each collection and class via a property. public class Db { //... public IMongoCollection<Book> Books { get { return db.getcollection<book>("book"); } } } public IMongoCollection<Publisher> Publishers { get { return db.getcollection<publisher>("publisher"); } }

31 Getting started with C# Step 4: Write some LINQ queries var db = new Db(); var popularbooks = (from b in db.books.asqueryable() where b.ratings.count > 100 select b).take(10).tolist();

32 Modeling relationships public class Book { public ObjectId Id { get; set; } public string Title { get; set; } public List<ObjectId> RatingIds { get; set; } } public class Rating { public ObjectId Id { get; set; } public ObjectId UserId { get; set; } public int Value { get; set; } } Standard "foreign key" style

33 Modeling relationships: embed public class Book { public ObjectId Id { get; set; } public string Title { get; set; } public List<Rating> Rating { get; set; } } public class Rating { public ObjectId UserId { get; set; } public int Value { get; set; } } Embedded document style

34 To Embed or Not Embed MongoDB support enforcing this relationship? yes and no à

35 To Embed or Not Embed MongoDB support enforcing this relationship? Yes

36 How do you decide? You must understand you common access patterns Do you usually want the reviews when you access a book? Embed reviews in books Do you often need reviews without books? Normalize with "weak" foreign keys

37 Is your collection embeddable? Bounded and relatively small? Consider embedding Large or potentially unbounded? You CANNOT embed it

38 Relationships: Demo

39 LINQ Gotchas Not all queries are support (but most are). A hybrid model will usually work best. from b in db.books.asqueryable() where b.ratings.count > 100 select new { b, b.ratings.count }; Crash from b in db.books.asqueryable().asenumerable() where b.ratings.count > 100 select new { b, b.ratings.count }; Client (from b in db.books.asqueryable() where b.ratings.count > 100 // server select b).asenumerable() // client.select(b => new { b, b.ratings.count }); Balanced

40 Inserting documents var cars = new[] { new Car() {Name = "Christine"}, new Car() {Name = "Corvette"}, }; db.cars.insertmany(cars);

41 Updating documents var updatedbooks = from b in db.books.asqueryable() where b.updateddate > newbooksdate select b; foreach (var b in updatedbooks) { b.title = "UPDATED: " + b.title; db.books.replaceone(book => book.id == b.id, b); } Replace the document with updated one by Id.

42 Updating documents public void Save<T>(T doc) where T: IHaveId { IMongoCollection<T> coll = this.getcoll<t>(); if (doc.id!= ObjectId.Empty) { var reslt = coll.replaceone(d => d.id == doc.id, doc); if (reslt.modifiedcount!= 1) throw new Exception("Failed to update document!"); } else { coll.insertone(doc); } } private IMongoCollection<T> GetColl<T>() { if (typeof(t) == typeof(book)) return this.books as IMongoCollection<T>; if (typeof(t) == typeof(publisher)) return this.publishers as IMongoCollection<T>; return null; }

43 Updating documents var updatedbooks = from b in db.books.asqueryable() where b.updateddate > newbooksdate select b; foreach (var b in updatedbooks) { b.title = "UPDATED: " + b.title; db.save(b); } Update or insert, nice and easy now.

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