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Posts tagged with 'database'

This blog post is a part of the 2022 C# Advent. Every day of Advent, two contributions from C# enthusiasts are revealed. Thanks for reading, and Merry Christmas!

I’ve written about How I use Fluent Migrator and Lessons learned about Fluent Migrator. I like using Fluent Migrator when I worked with relational databases.

However, I spend most of my time working with the NoSQL document database Couchbase, these days. If the idea of Fluent Migrator for Couchbase sounds interesting, read on!

What are database migrations?

Database migrations (not to be confused with data migrations) are a series of scripts/definitions that build the structure of a database. For instance, the first script could create 15 tables. The next script might alter a table, or add a 16th table. And so on.

Why are they important?

Having database migrations are important because they make sure anyone interacting with the database is on the same page, whether they’re working on a local database, test database, staging database, production, etc. Migrations can be part of the CI/CD process, as well.

What good is that for NoSQL?

If you’re not familiar with NoSQL, you might think that migrations wouldn’t make any sense. However, NoSQL databases (especially document databases), while flexible, are not devoid of structure. For instance, in place of Database/Schema/Table/Row, Couchbase has the concepts of Bucket/Scope/Collection/Document that roughly correspond.

It’s true that a NoSQL migration would not have as much predefined detail (there’s nowhere to specify column names and data types, for instance), but the benefits of migrations can still help developers working with Couchbase.

Introducing NoSqlMigrator for Couchbase

I’ve created a brand new project called NoSqlMigrator, to offer the same style of migration as Fluent Migrator.

Important notes:

  • This is not a fork or plugin of Fluent Migrator. It’s a completely separate project.

  • This is not an official Couchbase, Inc product. It’s just me creating it as an open source, community project.

  • It’s very much a WIP/alpha release. Please leave suggestions, criticisms, PRs, and issues!

Setting up migrations in C#

The process is very similar to Fluent Migrator.

  1. Create a project that will contain your migration classes (you technically don’t have to, but I recommend it).

  2. Add NoSqlMigrator from NuGet to that project.

  3. Create classes that inherit from Migrate base class. Define an Up and Down. Add a Migration attribute and give it a number (typically sequential).

  4. When you’re ready to run migrations, you can use the CLI migration runner, available as a release on GitHub, or you can use the MigrationRunner class, and run the migrations from whatever code you like. (I recommend the CLI).

Currently, NoSqlMigrator only supports Couchbase. Unlike the relational world, there is a lot of variance in structure and naming in the NoSQL world, so adding support for other NoSQL databases might be awkward (But I won’t rule that out for the far future).

Creating your first migration

Here’s an example of a migration that creates a scope and a collection (a bucket must already exist) when going "Up". When going down, the scope is deleted (along with any collections in it).

public class Migration001_CreateInitialScopeAndCollection : Migrate
    public override void Up()

    public override void Down()

If you are new to migrations, the Down can sometimes be tricky. Not everything can be neatly "downed". However, I find that I tend to only use Down during development, and rarely does it execute in test/integration/production. But it is possible, so do your best when writing Down, but don’t sweat it if you can’t get it perfect.

Running the migration

Here’s an example of using the command line to run a migration:

> NoSqlMigrator.Runner.exe MyMigrations.dll couchbase://localhost Administrator password myBucketName

That will run all the Up implementations (that haven’t already been run: it keeps track with a special document in Couchbase).

You can also specify a limit (e.g. run all migrations up to/down from #5) and you can specify a direction (up/down). Here’s an example of running Up (explicitly) with a limit of 5:

> NoSqlMigrator.Runner.exe MyMigrations.dll couchbase://localhost Administrator password myBucketName -l 5 -d Up

More features for NoSQL migrations

Here are all the commands currently available:

  • Create.Scope

  • Create.Collection

  • Create.Index

  • Delete.Scope

  • Delete.Collection

  • Delete.FromCollection

  • Delete.Index

  • Insert.IntoCollection

  • Execute.Sql

  • Update.Document

  • Update.Collection

I’m working on a few more, and I have some GitHub issues listing commands that I plan to add. But if you can think of any others, please create an issue!

Tips and Conclusion

Many of the Lessons learned still apply to NoSqlMigrator.

In that post, I mention Octopus, but imagine any CI/CD/deployment tool of your choice in its place (e.g. Jenkins, GitHub Actions, etc).

I think NoSqlMigrator can be a very handy tool for keeping databases in sync with your team, checking knowledge into source control, and providing a quick way to get a minimum database structure built, to make your day of coding a little easier.

Please give it a try in your own project! If you’ve not used Couchbase, check out a free trial of Couchbase Capella DBaaS.

Jeffrey Miller is using Neo4j. This episode is sponsored by Smartsheet.

Show Notes:

Want to be on the next episode? You can! All you need is the willingness to talk about something technical.

Music is by Joe Ferg, check out more music on!

This is a repost that originally appeared on the Couchbase Blog: .NET Core List, Queue, and Dictionary Data Structures backed by Couchbase.

The addition of the sub-document API to Couchbase 4.5 has paved the way for efficient data structure support in Couchbase.

In this blog post, I’m going to show a demo of three types of data structures you can use with the Couchbase .NET SDK:

  • List - a list of objects, basically a List<T> backed by Couchbase

  • Queue - a queue of objects, basically a Queue<T> backed by Couchbase

  • Dictionary - a dictionary of objects, basically a Dictionary<K,T> backed by Couchbase

I’ll also discuss a little bit how this works behind the scenes.

You can play along at home if you like. The source code for this blog is available on GitHub, and Couchbase Server is free to download (developer previews of version 5 are currently available monthly).


A List<T> is a .NET data structure that is held in memory. With the data structures provided by the Couchbase .NET SDK, you can store it in a Couchbase document.

To create a Couchbase-backed List:

var list = new CouchbaseList<dynamic>(bucket, "myList");

The string "myList" corresponds to the key for the document that will contain the list. When using CouchbaseList<T>, a single document with that key will be created (if one doesn’t exist already). If a document by that key already exists, CouchbaseList will use it.

You can now add/remove items from the list and that will all be persisted to the document. You can also perform other operations like getting a count of the items in the list.

// add 10 objects to the list
for(var i = 0; i < 10; i++)
    list.Add(new { num = i, foo = "bar" + Guid.NewGuid()});

// remove an item from the list by index

// show an item from the list by index
Console.WriteLine("5th item in the list: " + list[5].foo + " / " + list[5].num);

The above code would result in a document with a key "myList" that looks like below. Notice that the item with num of 5 is not listed, because it was removed.

There’s something subtle in the above example that needs to be pointed out. Notice that I used var item = list[5]; and then and item.num in the WriteLine. If I used list[5].foo and list[5].num directly, that would result in two different subdocument calls to Couchbase. Not only is this less than optimal efficiency, but it’s possible for the values to change between the two calls.

    "num": 0,
    "foo": "bara1fd74ee-a790-4a0f-843c-abe449cb8b1d"
    "num": 1,
    "foo": "bardc1d8f9a-4e93-46f9-b8ae-ec036743869e"
    "num": 2,
    "foo": "bar9a60abe9-1e04-4fba-bd1f-f1ec39d69f56"
    "num": 3,
    "foo": "bar9566605b-7abf-4a0c-aa9d-63b98ce86274"
    "num": 4,
    "foo": "bar6261323f-de50-42a7-a8a7-6fcafb356deb"
    "num": 6,
    "foo": "bar13832bcb-2aa0-491a-a01f-1d496f999ffc"

  // ... etc ...


Very similar to List, you can create a Couchbase-backed queue:

var queue = new CouchbaseQueue<dynamic>(bucket, "myQueue");

A queue is stored just like a list. The difference is that the ordering is significant, and this is reflected by the operations you perform on a queue: Enqueue and Dequeue.

for(var i = 0; i < 3; i++)
    queue.Enqueue(new { num = i, foo = "baz" + Guid.NewGuid()});

// dequeue
var item = queue.Dequeue();
Console.WriteLine("item num " + item.num + " was dequeued. There are now " + queue.Count + " items left in the queue.");

The above code would result in a document with a key "myQueue" (see JSON below). Notice there is no object in the array with num "0" because it was dequeued.

    "num": 1,
    "foo": "baz64bb62b6-bf23-4e52-b584-d2fa02accce6"
    "num": 2,
    "foo": "baz0a160bd9-aa7b-4c45-9e19-d1a3d982a554"


Hopefully you’re seeing a pattern now. To create a dictionary:

var dict = new CouchbaseDictionary<string,dynamic>(bucket, "myDict");

Again, a document will be created with the given key. The operations that can be performed include Add, Remove, and the indexer [] operation.

for(var i = 0; i < 5; i++)
    dict.Add("key" + Guid.NewGuid(), new { num = i, foo = "qux" + Guid.NewGuid()} );

// print out keys in the dictionary
Console.WriteLine("There are " + dict.Keys.Count + " keys in the dictionary.");
foreach(var key in dict.Keys)
    Console.WriteLine("key: " + key + ", value.num: " + dict[key].num);

A dictionary document looks like:

  "key5aa2520d-123c-4fca-b444-b0cb8846d46e": {
    "num": 0,
    "foo": "qux93b197dc-f175-4246-a38d-7b080eb9bea0"
  "key55dee298-14c6-4da7-97a8-66c69d7e8a70": {
    "num": 1,
    "foo": "quxa593ee4c-682c-402d-887b-3f09f029e9b6"
  "key3386afcf-7b70-4e4d-b9ae-6defbca33fe7": {
    "num": 2,
    "foo": "qux1259ae94-1008-4e1f-86a1-bfbd0873b09b"
  "key2bc8c451-f125-4282-9fb4-7ea15f4b3168": {
    "num": 3,
    "foo": "qux1b6fb62b-9918-46dc-9a2f-610a55d017ef"
  "key3f7041f3-abd3-49c7-a373-454cbd2ac0fc": {
    "num": 4,
    "foo": "qux0a87655f-197d-4fb2-8a54-b1de6e288de4"

A note about C# dynamic: I used dynamic to keep the code samples short and simple. In your application, you are probably better off using a real defined C# type. It all gets serialized to JSON in Couchbase, of course.

Behind the scenes

Before the subdocument API was released in Couchbase Server 4.5, these data structures were possible, of course. The catch was that you would be loading up the entire document, putting it in a list, making changes to the list, and then saving the entire document. If you have large data structures, but are only reading or making changes to a single item, this would often result in wasted time and wasted bandwidth and possibly increased contention.

The subdocument-API (which you can use directly; I covered it in the Sub-document API in Couchbase Server 4.5 with the .NET SDK (revisited) blog post) is used behind the scenes in CouchbaseList, CouchbaseQueue, and CouchbaseDictionary. So when you add an item to a CouchbaseList, for instance, only that item is being sent over the wire, not the entire list.

Some operations will still need to get the entire document. For instance, iterating through a collection using a foreach loop will retrieve the full document. Removing an item from a list will result in the full document being scanned. But if sub-document operations come along in the future to support those actions, the SDK implementations will be updated accordinging.


These data structures are another tool to help you manage your data. Since they use the sub-document API, they are generally more performant than a whole-document approach. For more detail, check out the Data Structures documentation.

Have questions? Feedback? Need help? Please visit our forums, ping me on Twitter @mgroves, or leave a comment.

I've just wrapped up my first week at Couchbase. So far, I like the job quite a bit.

One of the things I've been tasked with is to brainstorm a plan of things that Couchbase can do to reach out to developers, but specifically to Microsoft-oriented developers.

Couchbase love Microsoft

I've already talked to some of you for ideas, and I've created a huge list. The next step will be to pare down the list, prioritize it, and start working on it. But before I do that, let me send out one more appeal to developers of all kinds, including MS developers: what can I do to better communicate with and help you and your peers? Be as specific or general as you'd like!

Feel free to leave a comment below, hit me on Twitter via @mgroves, use my Contact Form, or email me directly matthew.groves AT couchbase DOT com

Matthew D. Groves

About the Author

Matthew D. Groves lives in Central Ohio. He works remotely, loves to code, and is a Microsoft MVP.

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