Sunday, May 19, 2013

What's the deal with NoSQL?

Everybody seems to be looking at and debating NoSQL these days, and so am I and I thought I'd say a few words about it. Which is not to say I haven't said stuff before, bit them I was mainly targeting specific attributes of many NoSQL solutions (like "eventual consistency" or, as you might call it, "instant inconsistency", What I was opposing is that "eventual consistency" has anything to do with just that, consistency. Rather, what this means is that at any point in time the system is inconsistent, and even if it might be consistent, you cannot rely on it being so. Which is fine, but don't call it consistency, call it inconsistency. Allowing a database to be somewhat inconsistent doesn't necessarily mean that it's something wrong with it).

All this said, what is going on here, why are we MySQL and MariaDB users seeing so many MongoDB, Cassandra and LevelDB applications pop up? Come on, these are typically less functional implementations of a database than even the most basic MySQL setup? No transactions, no joins, no standards etc. etc. And the answer, if you want to hear what I have to say, is ease of use. So let's explore that a bit.

Following the Object Orientation frenzy of the 1990s, when any application project ended up consisting of endless sessions modeling objects, usually involving expensive consultants, dresses in expensive, blue suits. And when that was done (which took years!) you had a way cool object model, but no money left to do the actual implementation, i.e. do the real programming (shiver), and you went to some other project and the nicely dressed object design consultant left to see another OO sucker.

Now, objects are much more standard, even non-OO languages have a big chunk of OO features, and these are used enhance programmer productivity and better code and design. Which is fine (except that if you were one of those OO consultants, which means you are now out of a job, as such mundane tasks of writing is not something you would ever do, such dirty stuff is better left to "programmers". Oh no, I forgot that you are now an ITIL consultant, that just slipped my mind) but how does this relate to MySQL and MariaDB. The answer is that MySQL, which was once considered real easy to use, no longer is as easy as it used to be. The Relational data model is still brilliant when you look at data as data, and that is how many of us look at it, so we go through the process of mapping data to objects, if that is what it takes. SQL and Java, PHP or whatever merges, and the application now contains a layer mapping objects to real data. Or we use hibernate, which does this automatically for us.

But a new cadre of developers are emerging, and they look at OO as natural and they look at objects as data (it's not. Data, in my mind, should be independent from the application using it, objects on the other hand, are closely tied to the application at hand). With which I do not mean that there is something wrong with building applications using objects, quite the opposite. But if all you know is objects, then using relational technology turns difficult, and SQL, for all the good things with it, seems old-fashioned and arcane, which it is (but it is so widely used you cannot avoid it). So you go with something that looks at objects as all you need, and present that in some object format. Like JSON.

And again, there is nothing wrong with that. But if we who are on the SQL and Relational track just discards these NoSQL technologies, we are not making any friends. We have to accept that MySQL and MariaDB really aren't that easy to use anymore, at least not for newcomers.

And then there is another thing: Some data, like Big Data, has attributes that really doesn't fit well in a relational model. Data where the attribute of a value can't easily be determined once and for all, and you need to reprocess that data (large test objects, images and maps are some examples). In this case, you really need to extend the relational model, somehow.

But SQL-based relational isn't going away. The Relational model is still one of the best ways to look at data, it's just that we also need some other ways of looking at data. And it needs to be easier to access. And we shouldn't really have to push SQL down the throat of every single developer, trying to develop an application using some OO technology. The answer is we need both. And these technologies needs to interoperate. I want to use SQL for my data. But I also want JSON and REST for my data. And there shouldn't be much of a performance overhead. All in all, we SQL folks need to wake up and data easier to use again. We know data better than the Cassandra and MongoDB folks. We know transactions better than them too. But they know how to work with developers who doesn't know who The Beatles were and make Relational easy to use for them, without them having to learn JSON (and now having to listen to a tirade about todays youngsters not knowing what real music is and that it died with John Lennon! What? You don't know who John Lennon was! That's exactly what I mean, you have no taste at all!).

Just my 2 cents...



Matty said...

Nice post Anders. I think 1 additional reason why we see NoSQL adoption is technology "fashion" - I've seen cases where an RDBMS would be an obvious choice for a project, but an alternative NoSQL technology is chosen purely because the developer wants the experience on his/her resume.

This doesn't lesson the importance of NoSQL, but it is a reality for some projects

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