CouchDB is schema-free

One of the most annoying parts of dealing with a traditional SQL database is that you invariably need to change your schemata. This can be done usually with some ALTER TABLE statements, but other times it requires scripts and careful use of transactions, etc. In CouchDB, the solution is to just start using your new schema. No migration needed. If it's a significant change, then you might need to change your views slightly, but nothing as annoying as what would be needed with SQL.

The other advantage of having no schema is that some types of data just aren't well suited to having a strict schema enforced upon them. My CouchDB-based lifestreaming application is a perfect example of the inherent flexibility of CouchDB's schemaless design is that all kinds of disparate information can be stored alongside each other and sorted and aggregated. There's also no reason that you need to use its schema-free nature this way. You could, for example, manually enforce a schema for certain databases, if needed.

CouchDB is RESTFUL HTTP

When is the last time you tried to install MySQL or PostgreSQL drivers for your web development platform of choice? If you're using apt-get it's not so bad, but for just about every other platform, it's a total pain to get these drivers up and running. With CouchDB, there's no need. It speaks HTTP. Want to create a new database? Send an HTTP PUT request. Want to retrieve a document from the database? Send an HTTP GET. Want to delete a database? Send an HTTP DELETE. As you can see, the API is quite straightforward and if a client library doesn't already exist for your language of choice (hint: it does), then it will take you only a few minutes to write one.

But the best part about this is that we already have so many amazing and well-tested tools to deal with HTTP. For example, let's say you want to store one database on one server and another database on another server? It's as simple as setting up nginx or perlbal or varnish as a reverse proxy and having each URL go to a different machine. The same thing goes for transparent caching, etc. Oh, and also, web browsers know how to speak HTTP, too. You could easily write whole web apps served only from CouchDB.

Map/Reduce

Map/Reduce will kill every traditional data warehousing vendor in the market. Those who adapt to it as a design/deployment pattern will survive, the rest won't.

Sounds like someone from Google must have said this, or some Hadoop evangelist, or maybe someone who works on CouchDB. In fact, this comes from Brian Aker, a MySQL hacker who was Director of Architecture at MySQL AB and is now developing the open source fork of MySQL named Drizzle (also a very exciting project in its own right). He's right, too. Google was on to something in a big way when they unveiled their whitepaper on Map/Reduce. It's not the be-all end-all for processing and generating large data sets, but it certainly is a proven technology for that task.

Brian talks about massively multi-core machines which seem the inevitability these days, and we will need to start writing logic that is massively parallelizable to take advantage of these masses of CPUs. Map/Reduce is one way to force ourselves to write logic that can be parallelized. It is a good choice for any new database system to adopt for this reason, and that's why it's great to see that CouchDB has adopted it. It's just one more reason why CouchDB rocks.

So much more

I could talk about how it can handle 2,500 concurrent requests in 10mb of resident memory usage. I could talk about its pluggable view server backends, so that instead of writing views in JavaScript you can write them in Python or any other language (given the correct bindings). I could talk about CouchDBX, which makes installing it on the Mac, quite literally, one click. I could even talk about how it's written in Erlang, with an eye towards scalability. Or maybe about how its database store is append-only.

I could talk about any of those things, and more. It just comes down to this: CouchDB rocks. But don't take my word for it--try it out for yourself!