MongoDB – Part 4 – Replication

CAP, the theorem behind MongoDB and most NoSQL databases, states that no distributed system can provide consistency, availability and partition tolerance. In this article I’m going to be writing about what MongoDB offers in the replication sector and how you can utilise replication to customise all aspects of the CAP theorem.

I’ll be covering: how to create replication sets, how replication works in MongoDB, how to configure individual nodes in a set, how to retrieve the status of nodes, how to configure write concern when executing queries and common CAP configurations.

Continue reading →

MongoDB – Part 3 – Indexes

It has been a while since my last post on MongoDB, but I’m back and looking to finish off this series over the next 6-8 weeks (Edit: 6-8 months). Anyway, in this article I’m going to be covering all of the different types of indexes you can use in MongoDB

Most of these you’ll have heard of before, providing you’ve used almost any other DBMS. I’ll be providing examples of how to create each index, when you would want to use them and at the end I’ll throw together a few must know tips.

Continue reading →

MongoDB – Part 2 – Databases

OK. So in part 1 we covered a bunch of MongoDB basics. In this part, I plan on covering in detail the core MongoDB databases, what collections they have and what they’re used for.

When you first install MongoDB, two databases are created for you called admin and local. They don’t contain many collections and may not even contain any to begin with, however don’t worry about this, Mongo will create them as an when it needs them.

The third core database is called config. Config databases are a little more complicated, in that they can only be accessed when connected to a shard instead of a particular daemon. I haven’t covered shards yet. But for now just think of shards as individual mongod nodes, that all together form your data set. How this happens is very customisable, these customisable setting are stored in the config database. I’ll cover shards in great detail in a separate post.

Edit: Learn about MongoDB shards

Continue reading →

MongoDB – Part 1 – Collections, CRUD, Modifiers, Commands

Recently I’ve been posting a lot of articles about database and more specifically NoSQL. I’ve given a quick overview of each of the NoSQL database types as well as an overview of common concepts that appear throughout most NoSQL databases. Now I want to focus on a specific NoSQL database and I have Chosen MongoDB.

MongoDB is the most popular NoSQL database out there right now and you don’t have to take my word for it. Looking at Google Trends, you can see that MongoDB is getting more searches than Redis, Neo4j and Cassandra combined. Each of these databases are leading the way for their own database model (key-value, document, column and graph). So if you plan on learning a new database, MongoDB is without a doubt a fantastic choice. I’ve personally really enjoyed working with it the last 3 months and can see it being a popular choice for a very long time.

Continue reading →