Introduction

I don’t know how many of you work with SQL. Loads? Well I do, as we know it’s  a relational database which we can store um well relational SQL data types in,  such as INT/CHAR/NVARCHAR etc etc, I am sure you all know what I am talking  about and have used relational databases loads in the past.

Do you think there are other sort of databases out there? No? Well actually  there are some different types of databases other than relational databases,  such as

• Flat file
• Object
• NoSQL / Document / KeyValue pair

Now I do not profess to know much about Flat file or Object databases per se,  but I have spent some time evaluating and getting to know some of the newer  Document databases. In this article I have chosen to look at 3 different  Document databases, which I have created demos for in the code attached to this  article, but before we go on to talk about each of them and how to get started  with them, let’s just spend a bit of time talking about the gaining popularity  of these document databases.

 

So I have stated that this article will talk about document databases, but  what are these document databases, and why might you want to use one.

The reason to use a document database may come from any number of  requirements, such as

• A more accurate representation of your business model may be able to be expressed if you ditch the relational model
• RESTFul API (though most users would try and find a native client for their language of choice)
• Schema changes do not really matter as much as they would in a relational database, ad-hoc changes to the schema are supported

So those are some of the reasons, how about looking at some of the features  that a typical document database might minimally provide:

• Http enabled server, which is capable of handling standard HTTP requests for data (think PUT/GET/POST/DELETE), so if there was no driver for your language of choice available you could always just use standard Http requests.
• Documents are typically stored as some sort of serializable format (most typically this appears to be JSON or BSON)
• The abilty to store an entire document. Yes I mean a document in comparison to a rich object, with methods inheritence heirachy etc etc. These are not present in a document database; code is not part of the database.
• Sharding
• Replication

One thing that is of note when working with document databases, is this idea  of “eventual consistency”, which is not what we might be used to seeing by and  large, in the relational world.

What is meant by this term, it sounds scary right. Well I guess it is a bit,  but when working with document databases, its seems a common approach that they  all follow, to allow you to push updates/inserts into the document store, but  that does not mean these will be changes will be nesecarrily seen by all readers  of the data straight away They will of course be written to to all reader  sources eventually, but not straight away. Which means we may occassionally see  inconsistencies.

Why is this, how has it come about.  It’s all about scaling and  availability really, if you only have a single source of data, a you do  typically in a relational database world, then you must lock reads while you are  writing. It’s a simple model but it remains totally consistent, but it will not  scale that well, some of sort of sharding must be used, which is not that common  in relational databases. In fact having never done that is a RDBMS I am not sure  its even possible, may be it is maybe not.

Anyway that is one area I thought I would alert you to straight away, I  found these links to be highy informative on this subject, should you want to  know more

1. http://ayende.com/blog/4447/that-no-sql-thing (Ayende wrote RavenDB, so its worth a read)
2. http://smoothspan.wordpress.com/2007/12/22/eventual-consistency-is-not-that-scary/

You may find that this alone is reason enough that document databases may not  be a good fit for you, but that is a decison only you can make

Anyway you do not need to be too concerned with these issues, as this article  will be more focussed on elementary usage of  document databases, such as  how to perform simple CRUD operations, I just thought it was worth mentioning  upfront, so you knew about it, so there we go you have been warned.

Now there are loads and loads of document databases out there, far too many  for me to go through, for my initial evaluations I chose to look at a few based  on what I perceived to be the best attributes, such as

• Features
• Ease of use
• Reputation
• .NET driver availability (I am a .NET developer these day, so this article is about using .NET with the relevant document database)

With those list of attributes, I ended up with quite a large list, which I  whittled down further to end up with 3 document databases, which I will talk  about in this article.

1. Redis
2. Raven
3. Mongo

Do not expect to reach the end of this article and be an expert in document  databases, but I would hope by the end of reading this article you will be able  to understand how they work (kinda) and would be able to carry on using them and  finding any remaining answers you need by yourselves.

 

PreRequisites

Before we start you will need to make sure you have downloaded the relevant NoSQL server and .NET client APIs.  I would have liked to have upload them with this article but unfortunately they  are just too big for codeprojects limits, so this task must fall to you. So  shown below are the components you will need to download

Redis

For Redis you will need to download the following 3 items, and ensure the  correct .NET portions are references correctly

Server

1. This can be downloaded from : http://redis.io/download
2. Ensure you change the strings at the top of RedisServer.cs class within the DocumentDB.Redis project

.NET Client : Service Stack

1. This can be downloaded from : https://github.com/ServiceStack/ServiceStack.Redis
2. Once you have downloaded this ensure you fix all the references within the DocumentDB.Redis project

 

 

Raven

For Raven you will need to download the following 2 items, and ensure the  correct .NET portions are references correctly

Server

1. This can be downloaded from : http://builds.hibernatingrhinos.com/builds/RavenDB
2. Ensure you change the strings at the top of RavenServer.cs class within the DocumentDB.Raven project

.NET Client

1. The .NET client actually comes as part of the overall download mentioned above
2. Once you have downloaded Raven ensure you fix all the references within the DocumentDB.Raven project

 

MongoDB

For MongoDB you will need to download the following 2 items, and ensure the  correct .NET portions are references correctly

Server

1. This can be downloaded from : http://www.mongodb.org/downloads
2. Ensure you change the strings at the top of MongoDBServer.cs class within the DocumentDB.Mongo project

.NET Client (Mongo supported client)

1. This can be downloaded from : https://github.com/mongodb/mongo-csharp-driver/downloads
2. Once you have downloaded this ensure you fix all the references within the DocumentDB.Mongo project

 

1. Ensure each of the 3 projects within the downloadable demo code attached to this article, has its references fixed to point to where you downloaded the .NET client API Dlls to, which I am hoping you did when you following the steps above. If not make sure to do that now
2. Within each of the 3 projects within the downloadable demo code attached to this article is a simple server wrapper which simply spawns the correct actual NoSQL server process. This is more for convience than anything else, and you will need to change the path to the actual NoSQL server location to match where you downloaded it to. This is done by changing a string value within each of the XXXXServer.cs classes in the 3 demo projects within the downloadable demo code attached to this article.

Just for the record, when I was developing the code for  this article I put the NoSQL servers/.NET Clients with the downloadable solution  something like shown below, but you put them where you want, and just make sure  to do the 2 steps above for all 3 projects in the demo code

Redis Document Database Usage

In this section I will discuss usingRedis. Redis commands are at the  core of Redis, where a full list of commands can be found athttp://redis.io/commands, here is screen  shot to show you the sort of thing I am talking about

This screen shot shows only a small portion of the available Redis commands.

Now even though this is how Redis works internally there is not really a need  for you to get to know these commands, as any Redis client will already be  calling these commands on your behalf when it talks to the server. I just  thought it might be useful to show you how redis works under the hood.

One other very import aspect of getting to know Redis is that fact that it is  designed to work with extremely dynamic datasets, as such it is really intended  that your entire dataset should fit into memory. This may sound mad, but it  really depends on the type of application you need to write.

Although Redis operates in memory it does have multiple disk persistance modes i.e Journalling and/or entire snapshots. See this link for more information on this http://redis.io/topics/persistence

If you want years and years or storage that you could bring back into memory at any time then  Redis may not be a good fit for you. On the other had is you have some very  dynamic fast moving data, that you could live with expiring after x-time, then  Redis would be a very good fit.

 

The Server

The Redis server (available for download here :http://redis.io/download) is witten in C and can be run using  the “redis-server.exe” process. In fact when you have downloaded  Redis server  you should see something like this

Where there are a number of different processes that can be used for managing  Redis server.

The .NET Client

There are quite a few Redis clients for all sorts of languages. This aricles  demo code uses .NET, so I obviously had to pick a .NET client, but which one.  Well that was down to me doing a bit of research and picking one, and it seemed  that ServiceStack seemed to be quite popular, so that is the one I chose. It can  be foud here: https://github.com/ServiceStack/ServiceStack.Redis

It would be  pretty much impossible for me to outline every feature of Reis, but I shall  outline what I think are the most important parts when getting started with  Redis.

1st Steps

You must have the Redis actual server running. I have tried to make this  easy for by creating a helper class called “RedisServer” which  you should modify to point to your Redis server downloads. Once the Redis actual  server is running we need to create a software RedisClient (which  connects to the actual Redis server instance).

Some skeleton code is shown below, that all the Redis code uses in the  attached demo code

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using ServiceStack.Redis;

namespace DocumentDB.Redis
{
    public class Program
    {
        [STAThread]
        static void Main(string[] args)
        {
            Run();
        }

        public static void Run()
        {
            try
            {
                RedisClient redisClient = new RedisClient("localhost");

                if (RedisServer.Instance.Start())
                {
                   //Use the software RedisClient which talks to actual Redis server
                   //Use the software RedisClient which talks to actual Redis server
                   //Use the software RedisClient which talks to actual Redis server
                   //Use the software RedisClient which talks to actual Redis server
                }
            }
            catch (Exception ex)
            {
                Console.WriteLine("============= OH NO : ERROR ============");
            }
            Console.ReadLine();

        }
    }
}

This software RedisClient is then used by the various classes in  the demo code, so you can expect to see the use of  a RedisClient object in use in the attached demo code

 

Basic CRUD Using Typed Objects

In order to show you how to use my chosen Redis client (Service Stack) all  you really need to know how to do is use an instance of a RedisClient which would typically be used as follows, to obtain a IRedisTypedClient

private IList<Blog> Blogs()
{
    return redisClient.As<Blog>().GetAll();
}

Shown below are various listings that show how to carry out various operations using the  Service Stack RedisClient where the following document classes are used to store

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace DocumentDB.Redis
{
    public class Blog
    {
        public Blog()
        {
            this.Tags = new List<string>();
            this.BlogPostIds = new List<long>();
        }

        public long Id { get; set; }
        public long UserId { get; set; }
        public string UserName { get; set; }
        public List<string> Tags { get; set; }
        public List<long> BlogPostIds { get; set; }
    }

    public class BlogPost
    {
        public BlogPost()
        {
            this.Categories = new List<string>();
            this.Tags = new List<string>();
        }

        public long Id { get; set; }
        public long BlogId { get; set; }
        public string Title { get; set; }
        public string Content { get; set; }
        public List<string> Categories { get; set; }
        public List<string> Tags { get; set; }
    }

    public class User
    {
        public User()
        {
            this.BlogIds = new List<long>();
        }

        public long Id { get; set; }
        public string Name { get; set; }
        public List<long> BlogIds { get; set; }
    }
}

Obtain Data

private IList<Blog> Blogs()
{
    return redisClient.As<Blog>().GetAll();
}

private IList<User> Users()
{
    return redisClient.As<User>().GetAll();
}

Insert Data

private void InsertSingleBlog(IRedisClient client)
{

    var redisUsers = client.As<User>();
    var redisBlogs = client.As<Blog>();
    var redisBlogPosts = client.As<BlogPost>();
    var ayende = new User { Id = redisUsers.GetNextSequence(), Name = "Oren Eini" };

    var ayendeBlog = new Blog
    {
        Id = redisBlogs.GetNextSequence(),
        UserId = ayende.Id,
        UserName = ayende.Name,
        Tags = new List<string> { "Architecture", ".NET", "Databases" },
    };

    var blogPosts = new List<BlogPost>
	{
		new BlogPost
		{
			Id = redisBlogPosts.GetNextSequence(),
			BlogId = ayendeBlog.Id,
			Title = "RavenDB",
			Categories = new List<string> { "NoSQL", "DocumentDB" },
			Tags = new List<string> {"Raven", "NoSQL", "JSON", ".NET"}
		}
	};

    ayende.BlogIds.Add(ayendeBlog.Id);
    ayendeBlog.BlogPostIds.AddRange(blogPosts.Where(x => x.BlogId == ayendeBlog.Id).ConvertAll(x => x.Id));

    redisUsers.Store(ayende);
    redisBlogs.StoreAll(new[] { ayendeBlog });
    redisBlogPosts.StoreAll(blogPosts);

}

It can be see that using the IRedisClient we are able to use batch operations such as StoreAll which makes things easy for us

Delete Data

private void DeleteSpecificBlog(long blogId)
{
    Console.WriteLine("DELETING SINGLE Blog\r\n");
    var redisBlogs = redisClient.As<Blog>();
    redisBlogs.DeleteById(blogId);
}

An important IMPORTANT note here is that the Save() method here is not quite what it seems. This actually does a foreground/synchronous snapshot save to disk – you generally never want to do this in Production. You would be better of doing a BGSAVE (background save) for Production environments

Linq Support

As I have already stated on numerous occassions Redis works with in memory  datasets, that is the entire dataset MUST fit into memory as such it exposes  numerous collection classes for managing the in memory store. Within the Service  Stack Redis client these collections are typically managed using standard .NET  collection classes, as such any of the standard LINQ extension methods may be  applied straight to the collections. For example here is where I get a List<Blog> items, and filter it using LINQ

private IList<Blog> Blogs()
{
    IList<Blog> blogs = new List<Blog>();
    var redisBlogs = redisClient.As<Blog>())
    blogs = redisBlogs.GetAll().Where(x => x.Id > 20).ToList();
    return blogs;
}

It should of course be noted that since Redis works with a in memory dataset, it is not using a true IQueryProvider, and it really just using Linq to objects, there is no lazy loading occurring in the database. So just be mindful of this fact

 

Transaction Support

Within the Service Stack Redis client, transactions are managed by obtaining  a new IRedisTransaction of the IRedisClient by using  the CreateTransaction() method, after you have a IRedisTransaction you can simply use the following methods to work with  the IRedisTransaction

• QueueCommand(..) : Will inlist the contained command in the transaction
• Rollback() : Will rollback the transaction
• Commit() : Will commit the transaction

Anyway here is some demo code

public void InsertInsideTransaction(bool shouldTransactionRollback)
{
    RedisClient transClient = new RedisClient("localhost");

    ClearAll();
    using (var trans = transClient.CreateTransaction())
    {
        var redisUsers = redisClient.As<User>();

        //Have to do this here (as redisUsers.GetNextSequence() is a READ, which MUST be done before
        //we write using the RedisTransaction)
        var sacha = new User { Id = redisUsers.GetNextSequence(), Name = "Sacha Barber" };

        trans.QueueCommand(r =>
            {
                using (redisUsers = r.As<User>())
                {
                    redisUsers.Store(sacha);
                }
            });

        //commit or rollback based on incoming flag
        if (shouldTransactionRollback)
            trans.Rollback();
        else
            trans.Commit();

        IList<User> users = Users();
        Console.WriteLine(string.Format("InsertInsideTransaction : There are currently {0}, Users", users.Count()));
    }
}

 

Cache Expiry

Sorry to harp on and on about this, but the point that makes Redis so fast is  that it works with the dataset entirely in memory. So what happens to data you  no need, is there a way to delete is, well yeah we could do it programatically,  but is there a way of use Redis as some sort of Most Recently Used (MRU) cache  where data can expire on its own?

Turns out this is possible and what we need to do is use one of the standard  Redis Service Stack typed client methods ExpireIn which has a  method signature which looks like this

bool ExpireIn(object id, TimeSpan expiresAt);

To see this in action I have provided a bit of code in the demo which is as follows

public void CacheInsertWhichDeletes()
{
    ClearAll();

    var redisUsers = redisClient.As<User>();
    var frankenFurter = new User { Id = redisUsers.GetNextSequence(), Name = "FrankenFurter" };
    redisUsers.Store(frankenFurter);
    redisUsers.ExpireIn(frankenFurter.Id, TimeSpan.FromSeconds(1));

    User fetchedUser = redisUsers.GetById(frankenFurter.Id);
    Console.WriteLine(fetchedUser != null ? "Still exists" : "Removed from cache");
    Thread.Sleep(2000);
    fetchedUser = redisUsers.GetById(frankenFurter.Id);
    Console.WriteLine(fetchedUser != null ? "Still exists" : "Removed from cache");
}

So that is how you might manage fast moving data that you only want to live for x amount of time.

 

Pooling

Service Stack (The Redis Client I chose to use) does offer connection pooling  via the use of 2 classes PooledRedisClientManager and any class of  your own that implements the Servce Stack interface IRedisClientFactory

The following code declared multiple client addresses

readonly string[] testReadWriteHosts = new[] {
	"readwrite1", "readwrite2:6000", "192.168.0.1", "localhost"
};

readonly string[] testReadOnlyHosts = new[] {
	"read1", "read2:7000", "127.0.0.1"
};

Where we then proceed to create a PooledRedisClientManager like this

private PooledRedisClientManager CreateAndStartManager()
{
    var manager = CreateManager();
    manager.Start();
    return manager;
}

private PooledRedisClientManager CreateManager()
{
    return CreateManager(new RedisClientFactory(), testReadWriteHosts, testReadOnlyHosts);
}

private PooledRedisClientManager CreateManager(
    IRedisClientFactory clientFactory, string[] readWriteHosts, string[] readOnlyHosts)
{
    return new PooledRedisClientManager(readWriteHosts, readOnlyHosts,
        new RedisClientManagerConfig
        {
            MaxWritePoolSize = readWriteHosts.Length,
            MaxReadPoolSize = readOnlyHosts.Length,
            AutoStart = false,
        })
    {
        RedisClientFactory = clientFactory
    };
}

Where it can be seen that we set a RedisClientFactory to an instance of IRedisClientFactory.  So what does that look like well it looks like this

public class RedisClientFactory : IRedisClientFactory
{
    public RedisClient CreateRedisClient(string host, int port)
    {
        return new RedisClient(host, port);
    }
}

After following these steps all that is left to do is spin up some and use a new PooledRedisClientManager. We get access to a client via the use of the PooledRedisClientManager. In the demo code I spin up new clients in new threads to simulate concurrent access to the connection pool, here is the relevant code

/// <summary>
/// Use the PooledRedisClientManager to gain access to n-many clients
/// </summary>
public void Start()
{
    Thread t = new Thread((state) =>
        {

            const int noOfConcurrentClients = 5; //WaitHandle.WaitAll limit is <= 64
            var clientUsageMap = new Dictionary<string, int>();

            var clientAsyncResults = new List<IAsyncResult>();
            using (var manager = CreateAndStartManager())
            {
                for (var i = 0; i < noOfConcurrentClients; i++)
                {
                    var clientNo = i;
                    var action = (Action)(() => UseClient(manager, clientNo, clientUsageMap));
                    clientAsyncResults.Add(action.BeginInvoke(null, null));
                }
            }

            WaitHandle.WaitAll(clientAsyncResults.ConvertAll(x => x.AsyncWaitHandle).ToArray());

            Console.WriteLine(TypeSerializer.SerializeToString(clientUsageMap));

            var hostCount = 0;
            foreach (var entry in clientUsageMap)
            {
                hostCount += entry.Value;
            }

        });
    t.SetApartmentState(ApartmentState.MTA);
    t.Start();
}

private static void UseClient(IRedisClientsManager manager, int clientNo,
    Dictionary<string, int> hostCountMap)
{
    using (IRedisClient client = manager.GetClient())
    {
        lock (hostCountMap)
        {
            int hostCount;
            if (!hostCountMap.TryGetValue(client.Host, out hostCount))
            {
                hostCount = 0;
            }
            hostCountMap[client.Host] = ++hostCount;
        }

        Console.WriteLine("Client '{0}' is using '{1}'", clientNo, client.Host);

        //YOU COULD USE THE SPECIFIC CLIENT HERE, YOU MAY HAVE TO TEST THE HOST TO SEE IF ITS THE ACTUAL ONE YOU WANT
        //YOU COULD USE THE SPECIFIC CLIENT HERE, YOU MAY HAVE TO TEST THE HOST TO SEE IF ITS THE ACTUAL ONE YOU WANT
        //YOU COULD USE THE SPECIFIC CLIENT HERE, YOU MAY HAVE TO TEST THE HOST TO SEE IF ITS THE ACTUAL ONE YOU WANT
        //YOU COULD USE THE SPECIFIC CLIENT HERE, YOU MAY HAVE TO TEST THE HOST TO SEE IF ITS THE ACTUAL ONE YOU WANT
    }
}

It is slightly backward in its usage in that you must ask the PooledRedisClientManager for a IRedisClient where it will use the IRedisClientFactory you  provided, and just give you a IRedisClient which you can use. But  which IRedisClient you get is up to the PooledRedisClientManager.  So if you are relying on it being a specific IRedisClient guess  again, you will need to check which IRedisClient has been dished  out by the PooledRedisClientManager.

 

 

Redis Admin UI

There is an Admin UI (which runs on .NET/Mono) which also includes JSON, XML, JSV & SOAP services for all Redis operations at: https://github.com/ServiceStack/ServiceStack.RedisWebServices/

 

Raven Document Database Usage

In this section I will discuss usingRaven.

There are a couple of points that are worth note before we start to look at  using Raven, so lets  give these a quick bit of discussion right now shall we:

1. Raven is written entirely in .NET, yes even the Server is .NET. I have seen plenty of chat/internet noise about this, and people saying that it would not be fast enough for high volume dataset demands. To be frank I am not in a position to say for sure whether this is the case or not, as I was just in an evaluation mode whilst looking at various different document databases. What I can say though is that for my evaluations I found no issues at all
2. Raven has a concept of denying unbounded results sets, so if you try and bring back to much data Raven will step in and not allow that. This is a setting that can be changed but it is not encouraged
3. Raven borrows ideas from other well known frameworks, mainly NHibernate, so when you see a IDocumentSession this should seem pretty familiar and almost be the same to use as ISession was/is in NHibernate.
4. The commercial version of Raven is not free, but its not that much if it fits your needs

 

The Server

The Raven server (available for download here : http://ravendb.net/download) is witten in C# and can be run using  the “Raven.Server.exe” process. In fact when you have downloaded  Raven server  you should see something like this

Where there are a number of different processes that can be used for managing  Raven server.

The .NET Client

There is only one .NET client for Raven which is the one available on the  download page: http://ravendb.net/download

It would be  pretty much impossible for me to outline every feature of Raven, but I shall  outline what I think are the most important parts when getting started with  Raven.

1st Steps

You must have the Raven actual server running. I have tried to make this  easy for by creating a helper class called “RavenServer” which  you should modify to point to your Raven server downloads. Once the Raven actual  server is running we need to create a software DocumentStore (which  connects to the actual Raven server instance).

Some skeleton code is shown below, that all the Raven code uses in the  attached demo code

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Raven.Client.Document;
using Raven.Client;
using System.IO;

namespace DocumentDB.Raven
{
    class Program
    {
        public static string documentStoreLocation = @"http://localhost:8080";

        [STAThread]
        static void Main(string[] args)
        {
            Run();
        }

        public static void Run()
        {
            try
            {
                if (RavenServer.Instance.Start())
                {
                    using (var documentStore = new DocumentStore { Url = documentStoreLocation, DefaultDatabase = "ravenTest" })
                    {
			//Use DocumentStore here
			//Use DocumentStore here
			//Use DocumentStore here
			//Use DocumentStore here
			//Use DocumentStore here
			//Use DocumentStore here
                    }
                }

            }
            catch (Exception ex)
            {
                Console.WriteLine("============= OH NO : ERROR ============");
            }
            Console.ReadLine();
        }
    }
}

This software DocumentStore is then used by the various classes in  the demo code, so you can expect to see the use of  a DocumentStore object in use in the attached demo code

 

Basic CRUD Using Typed Objects

In order to show you how to use my chosen Raven client all  you really need to know how to do is use an instance of a IDocumentSession which would typically be used as follows, where a Query is run using a  generic type of the Document that you would like to obtain data for

private IList<Blog> Blogs()
{
    IList<Blog> blogs = new List<Blog>();
    using (IDocumentSession session = documentStore.OpenSession())
    {
        blogs = session.Query<Blog>().ToList();
    }
    return blogs;
}

Shown below are various listings that show how to carry out various operations using the  Service Stack RedisClient where the following document classes are used to store

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace DocumentDB.Raven
{
    public class Blog
    {
        public Blog()
        {
            this.Tags = new List<string>();
            this.BlogPostIds = new List<long>();
        }

        public long Id { get; set; }
        public long UserId { get; set; }
        public string UserName { get; set; }
        public List<string> Tags { get; set; }
        public List<long> BlogPostIds { get; set; }
    }

    public class BlogPost
    {
        public BlogPost()
        {
            this.Categories = new List<string>();
            this.Tags = new List<string>();
        }

        public long Id { get; set; }
        public long BlogId { get; set; }
        public string Title { get; set; }
        public string Content { get; set; }
        public List<string> Categories { get; set; }a
        public List<string> Tags { get; set; }
    }

    public class User
    {
        public User()
        {
            this.BlogIds = new List<long>();
        }

        public long Id { get; set; }
        public string Name { get; set; }
        public List<long> BlogIds { get; set; }
    }

}

Obtain Data

private IList<Blog> Blogs()
{
    IList<Blog> blogs = new List<Blog>();
    using (IDocumentSession session = documentStore.OpenSession())
    {
        blogs = session.Query<Blog>().ToList();
    }
    return blogs;
}

private IList<User> Users()
{
    IList<User> users = new List<User>();
    using (IDocumentSession session = documentStore.OpenSession())
    {
        users = session.Query<User>().ToList();
    }

    return users;
}

Insert Data

public void InsertTestData()
{

    using (IDocumentSession session = documentStore.OpenSession())
    {
        var ayende = new User { Name = "Oren Eini" };
        var mythz = new User { Name = "Demis Bellot" };

        var ayendeBlog = new Blog
        {
            UserId = ayende.Id,
            UserName = ayende.Name,
            Tags = new List<string> { "Architecture", ".NET", "Databases" },
        };

        var mythzBlog = new Blog
        {
            UserId = mythz.Id,
            UserName = mythz.Name,
            Tags = new List<string> { "Architecture", ".NET", "Databases" },
        };

        session.Store(ayende);
        session.Store(mythz);
        session.Store(ayendeBlog);
        session.Store(mythzBlog);
        session.SaveChanges();

        var mythzBlogPosts = new List<BlogPost>
		{
			new BlogPost
			{
				BlogId = mythzBlog.Id,
				Title = "Redis",
				Categories = new List<string> { "NoSQL", "Cache" },
				Tags = new List<string> {"Redis", "NoSQL", "Scalability", "Performance"},
			},
			new BlogPost
			{
				BlogId = mythzBlog.Id,
				Title = "Couch Db",
				Categories = new List<string> { "NoSQL", "DocumentDB" },
				Tags = new List<string> {"CouchDb", "NoSQL", "JSON"},
			}
        };

        var ayendeBlogPosts = new List<BlogPost>
		{
			new BlogPost
			{
				BlogId = ayendeBlog.Id,
				Title = "RavenDB",
				Categories = new List<string> { "NoSQL", "DocumentDB" },
				Tags = new List<string> {"Raven", "NoSQL", "JSON", ".NET"} ,
			},
			new BlogPost
			{
				BlogId = ayendeBlog.Id,
				Title = "Cassandra",
				Categories = new List<string> { "NoSQL", "Cluster" },
				Tags = new List<string> {"Cassandra", "NoSQL", "Scalability", "Hashing"},
			}
        };

        foreach (BlogPost blogPost in ayendeBlogPosts.Union(mythzBlogPosts))
        {
            session.Store(blogPost);
        }

        session.SaveChanges();

        ayende.BlogIds.Add(ayendeBlog.Id);
        ayendeBlog.BlogPostIds.AddRange(ayendeBlogPosts.Select(x => x.Id));
        mythz.BlogIds.Add(mythzBlog.Id);
        mythzBlog.BlogPostIds.AddRange(mythzBlogPosts.Select(x => x.Id));

        session.Store(ayende);
        session.Store(mythz);
        session.Store(ayendeBlog);
        session.Store(mythzBlog);
        session.SaveChanges();

    }
}

 

Delete Data

private void DeleteSpecificBlog(long blogId)
{
    Console.WriteLine("DELETING SINGLE Blog\r\n");
    using (IDocumentSession session = documentStore.OpenSession())
    {
        session.Delete<Blog>(session.Query<Blog>().Where(x => x.Id == blogId).Single());
        session.SaveChanges();
    }
}

 

 

LINQ Support

As Raven is built entirely in .NET it would be pretty strange if it did not  support LINQ, and low and behold it does. For example here is where I get a List<Blog> items, and filter it using LINQ

private IList<Blog> Blogs()
{
    IList<Blog> blogs = new List<Blog>();
    using (IDocumentSession session = documentStore.OpenSession())
    {
        blogs = session.Query<Blog>().ToList();
    }

    return blogs;
}

 

Transaction Support

Raven supports transactions whole heartedly, and as Raven is all written in  .NET you even get to use familiar transaction classes such as TransactionScope, which I have to say does make life easier. Here is an  example of how to use Transactions with Raven.

public void InsertInsideTransaction(bool shouldTransactionRollback)
{

    var users = new List<User>();

    using (IDocumentSession session = documentStore.OpenSession())
    {
        try
        {
            users = session.Query<User>().ToList();
            Console.WriteLine(string.Format("Before Transaction : There are currently {0}, Users", users.Count()));

            using (var transaction = new TransactionScope())
            {
                var sacha = new User { Name = "Sacha Barber" };
                session.Store(sacha);
                session.SaveChanges();

                if (shouldTransactionRollback)
                    throw new InvalidOperationException("testing transactions");

                transaction.Complete();

            }
            users = session.Query<User>().ToList();
            Console.WriteLine(string.Format("After Transaction : There are currently {0}, Users", users.Count()));

        }
        catch
        {
            users = session.Query<User>().ToList();
            Console.WriteLine(string.Format("On Transaction Error : There are currently {0}, Users", users.Count()));
        }
    }
}

 

 

Direct Database Operations

Sometimes you just need direct access to the underlying Raven database  commands. In Raven this is done using the DocumentStore.DatabaseCommands  property which will give you an instance of a IDatabaseCommands,  which allows you to carry out the various tasks. Shown below is the IDatabaseCommandsinterface definition straight from Raven, which shows you what sort of things you can do with aIDatabaseCommands instance

using Raven.Abstractions.Commands;
using Raven.Abstractions.Data;
using Raven.Abstractions.Indexing;
using Raven.Client.Connection.Profiling;
using Raven.Client.Indexes;
using Raven.Json.Linq;
using System;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.IO;
using System.Net;

namespace Raven.Client.Connection
{
    // Summary:
    //     Expose the set of operations by the RavenDB server
    public interface IDatabaseCommands : IHoldProfilingInformation
    {
        // Summary:
        //     Gets or sets the operations headers
        NameValueCollection OperationsHeaders { get; set; }
        //
        // Summary:
        //     Gets a value indicating whether [supports promotable transactions].
        bool SupportsPromotableTransactions { get; }

        // Summary:
        //     Executed the specified commands as a single batch
        //
        // Parameters:
        //   commandDatas:
        //     The command data.
        BatchResult[] Batch(IEnumerable<ICommandData> commandDatas);
        //
        // Summary:
        //     Commits the specified tx id
        //
        // Parameters:
        //   txId:
        //     The tx id.
        void Commit(Guid txId);
        //
        // Summary:
        //     Deletes the document with the specified key
        //
        // Parameters:
        //   key:
        //     The key.
        //
        //   etag:
        //     The etag.
        void Delete(string key, Guid? etag);
        //
        // Summary:
        //     Deletes the attachment with the specified key
        //
        // Parameters:
        //   key:
        //     The key.
        //
        //   etag:
        //     The etag.
        void DeleteAttachment(string key, Guid? etag);
        //
        // Summary:
        //     Perform a set based deletes using the specified index, not allowing the operation
        //     if the index is stale
        //
        // Parameters:
        //   indexName:
        //     Name of the index.
        //
        //   queryToDelete:
        //     The query to delete.
        void DeleteByIndex(string indexName, IndexQuery queryToDelete);
        //
        // Summary:
        //     Perform a set based deletes using the specified index
        //
        // Parameters:
        //   indexName:
        //     Name of the index.
        //
        //   queryToDelete:
        //     The query to delete.
        //
        //   allowStale:
        //     if set to true [allow stale].
        void DeleteByIndex(string indexName, IndexQuery queryToDelete, bool allowStale);
        //
        // Summary:
        //     Deletes the specified index
        //
        // Parameters:
        //   name:
        //     The name.
        void DeleteIndex(string name);
        //
        // Summary:
        //     Disable all caching within the given scope
        IDisposable DisableAllCaching();
        //
        // Summary:
        //     Create a new instance of Raven.Client.Connection.IDatabaseCommands that will
        //     interacts with the specified database
        IDatabaseCommands ForDatabase(string database);
        //
        // Summary:
        //     Create a new instance of Raven.Client.Connection.IDatabaseCommands that will
        //     interacts with the default database
        IDatabaseCommands ForDefaultDatabase();
        //
        // Summary:
        //     Retrieves the document for the specified key
        //
        // Parameters:
        //   key:
        //     The key.
        JsonDocument Get(string key);
        //
        // Summary:
        //     Retrieves documents with the specified ids, optionally specifying includes
        //     to fetch along
        //
        // Parameters:
        //   ids:
        //     The ids.
        //
        //   includes:
        //     The includes.
        MultiLoadResult Get(string[] ids, string[] includes);
        //
        // Summary:
        //     Retrieves the attachment with the specified key
        //
        // Parameters:
        //   key:
        //     The key.
        Attachment GetAttachment(string key);
        //
        // Summary:
        //     Returns the names of all tenant databases on the RavenDB server
        //
        // Returns:
        //     List of tenant database names
        string[] GetDatabaseNames();
        //
        // Summary:
        //     Using the given Index, calculate the facets as per the specified doc
        IDictionary<string, IEnumerable<FacetValue>> GetFacets(string index, IndexQuery query, string facetSetupDoc);
        //
        // Summary:
        //     Gets the index definition for the specified name
        //
        // Parameters:
        //   name:
        //     The name.
        IndexDefinition GetIndex(string name);
        //
        // Summary:
        //     Returns the names of all indexes that exist on the server
        //
        // Parameters:
        //   start:
        //     Paging start
        //
        //   pageSize:
        //     Size of the page.
        string[] GetIndexNames(int start, int pageSize);
        //
        // Summary:
        //     Create a new instance of Raven.Client.Connection.IDatabaseCommands that will
        //     interact with the root database. Useful if the database has works against
        //     a tenant database
        IDatabaseCommands GetRootDatabase();
        //
        // Summary:
        //     Retrieve the statistics for the database
        DatabaseStatistics GetStatistics();
        //
        // Summary:
        //     Get the all terms stored in the index for the specified field You can page
        //     through the results by use fromValue parameter as the starting point for
        //     the next query
        IEnumerable<string> GetTerms(string index, string field, string fromValue, int pageSize);
        //
        // Summary:
        //     Retrieves the document metadata for the specified document key.
        //
        // Parameters:
        //   key:
        //     The key.
        //
        // Returns:
        //     The document metadata for the specifed document, or null if the document
        //     does not exist
        JsonDocumentMetadata Head(string key);
        //
        // Summary:
        //     Perform a single POST requst containing multiple nested GET requests
        GetResponse[] MultiGet(GetRequest[] requests);
        //
        // Summary:
        //     Sends a patch request for a specific document, ignoring the document's Etag
        //
        // Parameters:
        //   key:
        //     Id of the document to patch
        //
        //   patches:
        //     Array of patch requests
        void Patch(string key, PatchRequest[] patches);
        //
        // Summary:
        //     Sends a patch request for a specific document
        //
        // Parameters:
        //   key:
        //     Id of the document to patch
        //
        //   patches:
        //     Array of patch requests
        //
        //   etag:
        //     Require specific Etag [null to ignore]
        void Patch(string key, PatchRequest[] patches, Guid? etag);
        //
        // Summary:
        //     Promotes the transaction
        //
        // Parameters:
        //   fromTxId:
        //     From tx id.
        byte[] PromoteTransaction(Guid fromTxId);
        //
        // Summary:
        //     Puts the document in the database with the specified key
        //
        // Parameters:
        //   key:
        //     The key.
        //
        //   etag:
        //     The etag.
        //
        //   document:
        //     The document.
        //
        //   metadata:
        //     The metadata.
        PutResult Put(string key, Guid? etag, RavenJObject document, RavenJObject metadata);
        //
        // Summary:
        //     Puts a byte array as attachment with the specified key
        //
        // Parameters:
        //   key:
        //     The key.
        //
        //   etag:
        //     The etag.
        //
        //   data:
        //     The data.
        //
        //   metadata:
        //     The metadata.
        void PutAttachment(string key, Guid? etag, Stream data, RavenJObject metadata);
        //
        // Summary:
        //     Creates an index with the specified name, based on an index definition
        //
        // Parameters:
        //   name:
        //     The name.
        //
        //   indexDef:
        //     The index def.
        string PutIndex(string name, IndexDefinition indexDef);
        //
        // Summary:
        //     Creates an index with the specified name, based on an index definition that
        //     is created by the supplied IndexDefinitionBuilder
        //
        // Parameters:
        //   name:
        //     The name.
        //
        //   indexDef:
        //     The index def.
        //
        // Type parameters:
        //   TDocument:
        //     The type of the document.
        //
        //   TReduceResult:
        //     The type of the reduce result.
        string PutIndex<TDocument, TReduceResult>(string name, IndexDefinitionBuilder<TDocument, TReduceResult> indexDef);
        //
        // Summary:
        //     Creates an index with the specified name, based on an index definition
        //
        // Parameters:
        //   name:
        //     The name.
        //
        //   indexDef:
        //     The index def.
        //
        //   overwrite:
        //     if set to true [overwrite].
        string PutIndex(string name, IndexDefinition indexDef, bool overwrite);
        //
        // Summary:
        //     Creates an index with the specified name, based on an index definition that
        //     is created by the supplied IndexDefinitionBuilder
        //
        // Parameters:
        //   name:
        //     The name.
        //
        //   indexDef:
        //     The index def.
        //
        //   overwrite:
        //     if set to true [overwrite].
        //
        // Type parameters:
        //   TDocument:
        //     The type of the document.
        //
        //   TReduceResult:
        //     The type of the reduce result.
        string PutIndex<TDocument, TReduceResult>(string name, IndexDefinitionBuilder<TDocument, TReduceResult> indexDef, bool overwrite);
        //
        // Summary:
        //     Queries the specified index in the Raven flavoured Lucene query syntax
        //
        // Parameters:
        //   index:
        //     The index.
        //
        //   query:
        //     The query.
        //
        //   includes:
        //     The includes.
        QueryResult Query(string index, IndexQuery query, string[] includes);
        //
        // Summary:
        //     Resets the specified index
        //
        // Parameters:
        //   name:
        //     The name.
        void ResetIndex(string name);
        //
        // Summary:
        //     Rollbacks the specified tx id
        //
        // Parameters:
        //   txId:
        //     The tx id.
        void Rollback(Guid txId);
        //
        // Summary:
        //     Retrieves documents for the specified key prefix
        JsonDocument[] StartsWith(string keyPrefix, int start, int pageSize);
        //
        // Summary:
        //     Stores the recovery information
        //
        // Parameters:
        //   resourceManagerId:
        //     The resource manager Id for this transaction
        //
        //   txId:
        //     The tx id.
        //
        //   recoveryInformation:
        //     The recovery information.
        void StoreRecoveryInformation(Guid resourceManagerId, Guid txId, byte[] recoveryInformation);
        //
        // Summary:
        //     Returns a list of suggestions based on the specified suggestion query
        //
        // Parameters:
        //   index:
        //     The index to query for suggestions
        //
        //   suggestionQuery:
        //     The suggestion query.
        SuggestionQueryResult Suggest(string index, SuggestionQuery suggestionQuery);
        //
        // Summary:
        //     Perform a set based update using the specified index, not allowing the operation
        //     if the index is stale
        //
        // Parameters:
        //   indexName:
        //     Name of the index.
        //
        //   queryToUpdate:
        //     The query to update.
        //
        //   patchRequests:
        //     The patch requests.
        void UpdateByIndex(string indexName, IndexQuery queryToUpdate, PatchRequest[] patchRequests);
        //
        // Summary:
        //     Perform a set based update using the specified index
        //
        // Parameters:
        //   indexName:
        //     Name of the index.
        //
        //   queryToUpdate:
        //     The query to update.
        //
        //   patchRequests:
        //     The patch requests.
        //
        //   allowStale:
        //     if set to true [allow stale].
        void UpdateByIndex(string indexName, IndexQuery queryToUpdate, PatchRequest[] patchRequests, bool allowStale);
        //
        // Summary:
        //     Returns a new Raven.Client.Connection.IDatabaseCommands using the specified
        //     credentials
        //
        // Parameters:
        //   credentialsForSession:
        //     The credentials for session.
        IDatabaseCommands With(ICredentials credentialsForSession);
    }
}

Here is a small example of using it to add an index

this.documentStore.DatabaseCommands.PutIndex("Users/ByName",
                            new IndexDefinitionBuilder<User>
                            {
                                Map = users => from user in users
                                                select new { user.Name }
                            });

Full Text Search

One of the more interesting things that Raven allows you to do is to do full  text searches. To do this we would typically create an Index where we supply a  Map LINQ Exrpression to build the Index. Here is an example

public class User_ByName_FullTextSearch : AbstractIndexCreationTask<User>
{
    public User_ByName_FullTextSearch()
    {
        Map = users => from user in users
                        select new { user.Name };
        Index(x => x.Name, FieldIndexing.Analyzed);

    }

    public override string IndexName
    {
        get
        {
            return @"Users\ByNameIndex";
        }
    }
}

We would could then use this Index in a simple or complex manner as follows

Simple Case

Console.WriteLine(string.Format("Looking for users with Name starting with '{0}'\r\n", searchName));

Console.WriteLine("Simple starts with example:");
foreach (var person in Queryable.Where(session.Query<User, User_ByName_FullTextSearch>(), x => x.Name.StartsWith(searchName)))
{
    Console.WriteLine(person.Name);
}

Complex Case

Console.WriteLine(string.Format("Looking for users with Name starting with '{0}'\r\n", searchName));

Console.WriteLine("Simple starts with example:");
IQueryable<User> query = session.Query<User, User_ByName_FullTextSearch>();
query = searchName.Split().Aggregate(query, (current, part) => current.Where(x => x.Name.StartsWith(part)));

foreach (var person in query)
{
    Console.WriteLine(person.Name);
}

Where we would see the following results

 

 

Batch Operations

This section will outline how to carry out batch operations using Raven.

Bulk Updates

Sometimes you may need to update/delete a whole batch worth of data. Raven  supports these type of operations by using what it called “set based  operations”. To do “set based operations” in Raven you have to use its “patching  api”. We will now see some examples of how to use Ravens “patching api”.

As the heart of Ravens patching API are 2 objects that you will need to get  familiar with, which are

• PatchCommandData : A single batch operation for Document patch
• PatchRequest : A patch request for a specified Document

Here is an example of how to do a bulk update

public void DoUpdate(int numUsers)
{

    this.documentStore.DatabaseCommands.Batch(

        //patch 1st 1/2 of users
        Enumerable.Range(0, numUsers / 2).Select(i => new PatchCommandData
            {
                Key = "users/" + i,
                Patches = new[]
                {
                new PatchRequest
                {
                    Name = "Name",
                    Value = "Users-" + i
                },
            }
            }
    ).ToArray());

    this.documentStore.DatabaseCommands.Batch(

        //patch 1st 1/2 of users
        Enumerable.Range(numUsers / 2, numUsers).Select(i => new PatchCommandData
        {
            Key = "users/" + i,
            Patches = new[]
                {
                new PatchRequest
                {
                    Name = "Name",
                    Value = "Users-" + i
                },
            }
        }
    ).ToArray());

    using (IDocumentSession session = documentStore.OpenSession())
    {
        var users = session.Query<User>()
                        .Customize(x => x.WaitForNonStaleResults(TimeSpan.FromSeconds(10)))
                        .ToList();

        for (int i = 0; i < numUsers; i++)
        {
            Console.WriteLine("Expecting UserName of '{0}', actual UserName now is '{1}'", "Users-"
                + (i + 1), users[i].Name);
        }
    }

}

This code relies on there being an index which specifies an Index (which Raven builds using LINQ queries) to put a “UsersByName” index in place that thePatchRequest can use when its doing its bulk update to obtain the correct document.

this.documentStore.DatabaseCommands.PutIndex("Users/ByName",
                            new IndexDefinitionBuilder<User>
                            {
                                Map = users => from user in users
                                                select new { user.Name }
                            });

When run this code produces uutput something like this

 

Bulk Delete

To do a bulk delete we simply need an index in place, such the one we used  previously for the bulk update

this.documentStore.DatabaseCommands.PutIndex("Users/ByName",
                            new IndexDefinitionBuilder<User>
                            {
                                Map = users => from user in users
                                                select new { user.Name }
                            });

Then we can simply issue a DatabaseCommand to DeleteByIndex where we specify our Index string, and we also  supply an IndexQuery to pick out the documents we want to match,  which will then be deleted.

this.documentStore.DatabaseCommands.DeleteByIndex("Users/ByName",
    new IndexQuery
    {
        Query = "Name:*" // where entity.Name contains anything
    }, allowStale: false);

 

 

The Studio

Raven comes with a Sliverlight web client application called “The Studio”  which is a graphical front end tool that can be used to crry out various tasks  such as

• Manage collections/Indexes/Documents
• Edit Document
• Create Document
• Import Database (which uses the Smuggler.exe tool)
• Export Database (which uses the Smuggler.exe tool)

Here is a screen shot of a working Raven Studio instance reflecting some of  the demo code (click it for a bigger image)

 

 

 

MongoDB Document Database Usage

In this section I will discuss usingMongoDB

The Server

The MongoDB server (available for download here : http://www.mongodb.org/downloads) is witten in C++ and can be run using  the “mongod.exe” process. In fact when you have downloaded MongoDB  you should see something like this

Where there are a number of different processes that can be used for managing  MongoDB.

The .NET Client

The .NET client that this article uses is the official (supported) .NET  client, which can be downloaded from https://github.com/mongodb/mongo-csharp-driver/downloads. It would be  pretty much impossible for me to outline every feature of MongoDB, but I shall  outline what I think are the most important parts when getting started with  MongoDB.

1st Steps

You must have the MongoDB actual server running. I have tried to make this  easy for by creating a helper class called “MongoDBServer” which  you should modify to point to your MongoDB downloads. Once the MongoDB actual  server is running we need to create a software MongoServer (which  connects to the actual MongoDB server instance).

Some skeleton code is shown below, that all the MongoDB code uses in the  attached demo code

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using MongoDB.Bson;
using MongoDB.Driver;
using MongoDB.Driver.Linq;
using MongoDB.Bson.Serialization.Attributes;

namespace DocumentDB.Mongo
{
    class Program
    {
        public static void Run()
        {
            try
            {
                if (MongoDBServer.Instance.Start())
                {

                    MongoServer server = MongoServer.Create(); // connect to localhost
		    //Use the software server
		    //Use the software server
		    //Use the software server
		    //Use the software server
                 }
            }
            catch (Exception ex)
            {
                Console.WriteLine("============= OH NO : ERROR ============");
            }
            Console.ReadLine();
        }

        static void Main(string[] args)
        {
            Run();
        }
    }
}

This software MongoServer is then used by the various classes in  the demo code, so you can expect to see the use of  a MongoServerobject in use in the attached demo code

Raw Document Storage

So now that we have seen that we need to start the actual MongoDB server and  also a software MongoServer instance, let see how to store some  documents.

Here is some code that will store a BsonDocument which is what  MongoDB uses.

MongoDatabase rawDocumentDemoDB = server.GetDatabase("rawDocumentDemoDB");
rawDocumentDemoDB.Drop();

MongoCollection<BsonDocument> users = rawDocumentDemoDB.GetCollection("users");

// Create BsonDocument object for new user
var user = new BsonDocument();
user["firstname"] = "Goat";
user["lastname"] = "Head";
user["age"] = 12;
user["createdate"] = DateTime.Now;

// Insert new user object to collection
users.Insert(user);

And here is some code to update a BsonDocument

MongoDatabase rawDocumentDemoDB = server.GetDatabase("rawDocumentDemoDB");
rawDocumentDemoDB.Drop();

MongoCollection<BsonDocument> users = rawDocumentDemoDB.GetCollection("users");
var savedUsers = users.FindAll();
if (savedUsers.Any())
{
    BsonDocument userToModify = savedUsers.First();
    if (userToModify != null)
    {
        Console.WriteLine(string.Format("Decrementing User Id : {0}, Age By -1", userToModify["_id"]));
        userToModify["age"] = userToModify["age"].AsInt32 - 1;
        users.Save(userToModify);
    }
}

It can be seen that when working with MongoDB we are working closely withMongoCollection<T> which we can use to store BsonDocument objects in. But these BsonDocuments don’t seem  that handy, we don’t have any typing at all there, they are nothing more than a  dictionary of key/values, mmm not that useful. Surely there is a way we can  store our own object structures.

Well yes as it turns out there is, lets see that.

Serializing Your Own Types

Ok so we have seen hw to deal with BsonDocument objects and found them lacking, and we now want to serialize  our own objects, so how do we do that. Well its simply a question of doing the following:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using MongoDB.Bson.Serialization.Attributes;
using MongoDB.Bson;

namespace DocumentDB.Mongo
{
    public class Blog
    {
        public Blog()
        {
            this.Tags = new List<string>();
            this.BlogPostIds = new List<ObjectId>();
        }

        public ObjectId Id { get; set; }
        public ObjectId UserId { get; set; }
        public string UserName { get; set; }
        public List<string> Tags { get; set; }
        public List<ObjectId> BlogPostIds { get; set; }
    }
}

We can also customise the serialization process by using special Mongo attributes as shown below, where I have attributed the same Blog class:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using MongoDB.Bson.Serialization.Attributes;
using MongoDB.Bson;

namespace DocumentDB.Mongo
{
    public class Blog
    {
        public Blog()
        {
            this.Tags = new List<string>();
            this.BlogPostIds = new List<ObjectId>();
        }

        [BsonElementAttribute("id")]
        public ObjectId Id { get; set; }

        [BsonElementAttribute("userid")]
        public ObjectId UserId { get; set; }

        [BsonElementAttribute("username")]
        public string UserName { get; set; }

        [BsonElementAttribute("tags")]
        public List<string> Tags { get; set; }

        [BsonElementAttribute("blogpostids")]
        public List<ObjectId> BlogPostIds { get; set; }
    }
}

 

There are a couple of points here

1. That we use the BsonElementAttribute to mark our members as being serializable
2. That the Ids are using ObjectId, which is a MongoDB type. You can use long/int but if you use ObjectId you will get this Id automatically filled in by MongoDB
3. I have designed my models is to use links to Ids for foreign keys, this is  for 2 reasons
   1. I don’t want a massive graph brought back when I get a whole document stored, I want to decide when to fetch this linked data. So I just store the Ids of other data I may be interested in, if I find I need it, I’ll look it up later
   2. BSON/JSON doesn’t support circular references, so its just easier to store Ids, and have no cycles

Having this arrangement will allow these type of objects to be serialized to  Bson (Binary JSON)

I have to say I am not sure I like this too much, as its putting persistence  concerns in my model, I guess WCF does that with its DataContract/DataMember  attributes so its not so different, but WCF objects are more DTOs to me. But hey  you can decide if you like it or not.

Basic CRUD Using Typed Objects

I think the best way to show you some examples of basic CRUD operations using  strongly typed models is to literally show you a complete listing of the demo  code. So here goes

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;
using MongoDB.Driver;
using MongoDB.Driver.Linq;
using MongoDB.Bson;
using MongoDB.Driver.Builders;

namespace DocumentDB.Mongo
{
    public class MongoDemo
    {
        private MongoServer server;
        private MongoDatabase mongoDemoDB;

        public MongoDemo(MongoServer server)
        {
            this.server = server;
            mongoDemoDB = server.GetDatabase("rawDocumentDemoDB");
            mongoDemoDB.Drop();
        }

        public void ClearAll()
        {
            mongoDemoDB.Drop();
        }

        public void InsertFollowedByDelete()
        {
            StartRequest();
            ClearAll();
            InsertSingleBlog();
            IList<Blog> blogs = Blogs();
            Console.WriteLine(string.Format("There are currently {0}, Blogs", blogs.Count()));
            DeleteSpecificBlog(blogs.First().Id);
            blogs = Blogs();
            Console.WriteLine(string.Format("There are currently {0}, Blogs", blogs.Count()));
            StopRequest();
        }

        public void ShowListOfBlogs()
        {
            StartRequest();
            Console.WriteLine("RECENT BLOGS:\r\n");
            foreach (Blog blog in Blogs())
            {
                Console.WriteLine(blog.ToString());
            }
            StopRequest();
        }

        public int UserCount()
        {
            int users = 0;
            StartRequest();
            users = Users().Count();
            StopRequest();
            return users;
        }

        public void ShowListOfRecentPosts()
        {
            StartRequest();
            Console.WriteLine("RECENT BLOG POSTS:\r\n");
            foreach (BlogPost blogPost in BlogPosts())
            {
                Console.WriteLine(blogPost.ToString());
            }
            StopRequest();
        }

        public void InsertTestData()
        {
            StartRequest();
            ClearAll();
            var blogs = mongoDemoDB.GetCollection<Blog>("blogs");
            var users = mongoDemoDB.GetCollection<User>("users");
            var blogposts = mongoDemoDB.GetCollection<User>("blogposts");

            List<User> newUsers = new List<User>();
            User orenUser = new User { Name = "Oren Eini" };
            User demisUser = new User { Name = "Demis Bellot" };
            newUsers.Add(orenUser);
            newUsers.Add(demisUser);
            users.InsertBatch(newUsers);

            List<Blog> newBlogs = new List<Blog>();
            Blog orenBlog = new Blog
                {
                    UserId = orenUser.Id,
                    UserName = orenUser.Name,
                    Tags = new List<string> { "Architecture", ".NET", "Databases" },
                };
            Blog demisBlog = new Blog
                {
                    UserId = demisUser.Id,
                    UserName = demisUser.Name,
                    Tags = new List<string> { "Architecture", ".NET", "Databases" },
                };

            newBlogs.Add(orenBlog);
            newBlogs.Add(demisBlog);
            blogs.InsertBatch(newBlogs);

            List<BlogPost> newBlogPosts = new List<BlogPost>
            {
                new BlogPost
                {
                    BlogId = newBlogs.First().Id,
                    Title = "RavenDB",
                    Categories = new List<string> { "NoSQL", "DocumentDB" },
                    Tags = new List<string> {"Raven", "NoSQL", "JSON", ".NET"} ,
                },
                new BlogPost
                {
                    BlogId = newBlogs.First().Id,
                    Title = "Redis",
                    Categories = new List<string> { "NoSQL", "Cache" },
                    Tags = new List<string> {"Redis", "NoSQL", "Scalability", "Performance"},
                },
                new BlogPost
                {
                    BlogId = newBlogs.First().Id,
                    Title = "Cassandra",
                    Categories = new List<string> { "NoSQL", "Cluster" },
                    Tags = new List<string> {"Cassandra", "NoSQL", "Scalability", "Hashing"},
                },
                new BlogPost
                {
                    BlogId = newBlogs.First().Id,
                    Title = "Couch Db",
                    Categories = new List<string> { "NoSQL", "DocumentDB" },
                    Tags = new List<string> {"CouchDb", "NoSQL", "JSON"},
                }
            };

            blogposts.InsertBatch(newBlogPosts);
            orenUser.BlogIds.Add(orenBlog.Id);
            demisUser.BlogIds.Add(demisBlog.Id);
            users.Save(orenUser);
            users.Save(demisUser);

            orenBlog.BlogPostIds.Add(newBlogPosts.First().Id);
            demisBlog.BlogPostIds.Add(newBlogPosts.Last().Id);
            blogs.Save(orenBlog);
            blogs.Save(demisBlog);

            foreach (BlogPost newBlogPost in newBlogPosts)
            {
                newBlogPost.BlogId = orenBlog.Id;
                blogposts.Save(newBlogPost);
            }
        }

        private void InsertSingleBlog()
        {

            var blogs = mongoDemoDB.GetCollection<Blog>("blogs");
            var users = mongoDemoDB.GetCollection<User>("users");
            var blogposts = mongoDemoDB.GetCollection<User>("blogposts");

            User jayUser = new User { Name = "Jay Rays" };
            users.Insert(jayUser);

            Blog jayBlog = new Blog
            {
                UserId = jayUser.Id,
                UserName = jayUser.Name,
                Tags = new List<string> { "Architecture", ".NET", "Databases" },
            };
            blogs.Insert(jayBlog);

            BlogPost jayBlogPost = new BlogPost
            {
                Title = "RavenDB",
                Categories = new List<string> { "NoSQL", "DocumentDB" },
                Tags = new List<string> { "Raven", "NoSQL", "JSON", ".NET" }
            };
            blogposts.Insert(jayBlogPost);

            jayUser.BlogIds.Add(jayBlog.Id);
            jayBlog.BlogPostIds.Add(jayBlogPost.Id);
            jayBlogPost.BlogId = jayBlog.Id;

            users.Save(jayUser);
            blogs.Save(jayBlog);
            blogposts.Save(jayBlogPost);
        }

        private IList<Blog> Blogs()
        {
            return mongoDemoDB.GetCollection<Blog>("blogs").AsQueryable<Blog>().Where(x => true).ToList();
        }

        private IList<User> Users()
        {
            return mongoDemoDB.GetCollection<User>("users").AsQueryable<User>().Where(x => true).ToList();
        }

        private IList<BlogPost> BlogPosts()
        {
            return mongoDemoDB.GetCollection<BlogPost>("blogposts").AsQueryable<BlogPost>().Where(x => true).ToList();
        }

        private void DeleteSpecificBlog(ObjectId blogId)
        {
            Console.WriteLine("DELETING SINGLE Blog\r\n");
            mongoDemoDB.GetCollection<Blog>("blogs").Remove(Query.EQ("_id", blogId));
        }

        private void StartRequest()
        {
            server.RequestStart(mongoDemoDB);
        }

        private void StopRequest()
        {
            server.RequestDone();
        }
    }
}

I hope that makes sense to pick through, I feel it’s pretty obvious

SQL Like Syntax Expressions

One thing that MongoDB users seem to like is that it offers a SQL like API  via the use of Query classes. Here is a very small example that deletes a Blog that has a certain id

private void DeleteSpecificBlog(ObjectId blogId)
{
    Console.WriteLine("DELETING SINGLE Blog\r\n");
    mongoDemoDB.GetCollection<Blog>("blogs").Remove(Query.EQ("_id", blogId));
}

Here are some more example of Query methods that you might use

 

Linq Support

MongoDB does have support for LINQ where you simply use its collections and use the AsQueryable methods and you can also then do the typical LINQ like things such as the following:

return mongoDemoDB.GetCollection<Blog>("blogs").AsQueryable<Blog>().ToList();

Connection Sharing

One neat feature that MongoDB has is that is allows you to share a connection  to the database such that a group of operations can all use the same connection.

This is easily achieved using the following 2 methods

MongoDatabase rawDocumentDemoDB = server.GetDatabase("rawDocumentDemoDB");
server.RequestStart(rawDocumentDemoDB);
//DO STUFF HERE
//DO STUFF HERE
//DO STUFF HERE
//DO STUFF HERE
server.RequestDone();

Bulk Operations

MongoDB does allow bulk operations by the use of xxxBatch() methods of its collections, so an example might be InsertBatch(..), where a working example is as shown below

MongoDatabase rawDocumentDemoDB = server.GetDatabase("rawDocumentDemoDB");
rawDocumentDemoDB.Drop();

MongoCollection<BsonDocument> users = rawDocumentDemoDB.GetCollection("users");
List<User> newUsers = new List<User>();
User orenUser = new User { Name = "Oren Eini" };
User demisUser = new User { Name = "Demis Bellot" };
newUsers.Add(orenUser);
newUsers.Add(demisUser);
users.InsertBatch(newUsers);

Transaction Support

This is not something that MongoDB offers.

 

 

Comparisons

Whist evaluating the 3 document databases that I chose, these were my take  away points from them, as I say these are my own opionions and only I can be blamed  for them. I am also talking more from a beginners point of view as well, the  links I include below this table may help you if you are looking for deeper  answers, such as what sort of replication mechanisms are supported, but from a  purely zero to simple CRUD usability stance this is what I thought.

Redis	Raven	Mongo
As Redis uses an approach where the entire dataset must fit into memory, it is fast. Lightning fast in fact. Supports transactions Supports LINQ Good support for different types of collections Sets/Lists etc etc Values can expire Replication	Very feature rich Web based tool for inspecting/managing database store Supports transactions Supports LINQ Map/Reduce Full text search Bulk operations/Patching API Supports Sharding Embedded mode InMemory mod (for testing) No where near as fast as Redis (due to Redis everything in memory approach) Replication	Mature well used API NO support for transactions Supports LINQ (though there is some strangeness with LINQ API) Connection sharing Map/Reduce Bulk operations No where near as fast as Redis (due to Redis everything in memory approach) You need to polute your models with document storage attributes, poor seperation of concerns Replication

I also found these to be very good for making informed comparisons

1. http://kkovacs.eu/cassandra-vs-mongodb-vs-couchdb-vs-redis
2. http://stackoverflow.com/questions/4720508/redis-couchdb-or-cassandra
3. http://www.servicestack.net/mythz_blog/?p=474

In terms of which document database I would choose to use it would reall  depend on what I was trying to do, for example if I had a very quick changing  data such as FX Rate ticks/tweets which would quicky expire I would use Redis (I  also hear very good things about Cassandra for this sort of scenario, but I did  not look at that particular document database).

If I was dealing with more standard storage requirements, which is what  really drew us to look into a document database that was scalability, I would use  RavenDB as I found it to be much richer and better thought out than Mongo. Mongo  seemed like it had been written a while ago, and was showing signs of needing a  breath of fresh air, in fact I read somewhere that the guys behind Mongo are  starting ove again on a new project which I imagine will be great. However at  the time of writing this article, out of the document databases I looked at for  this scenario (ie not very fast moving data requirments) I would choose RavenDB.

 

That’s It

Thats all I wanted to say in this article, hope you have got something out of it, and enjoyed my rantings on this subject,  and can see that there may be times when a No SQL based solution may be exactly what you need