[alnayyir]

This is false, the writer of THE book on MySQL tuning (Jeremy Zawodny) is also the guy that is/has converted CraigsList to MongoDB from MySQL.

But let me interrupt your propaganda. We wouldn't want to address the reality that not all data and work sets can fit well in a relational database.

Example: http://blog.zawodny.com/2010/05/22/mongodb-early-impressions...

[Jach]

Calm down a bit, man. I've got a MongoDB mug sitting on my desk. I think you'd agree that even if the data structure fits into a key-value model more so than a relational one, that still doesn't mean you need NoSQL, and if you take a common definition of "big data" to mean "your data needs exceed the capabilities of a single machine", then a lot of people don't need all that scalability. (And if it did, you'd use Hadoop anyway. =P ) (There's also CAP Theorem considerations for added fun. http://en.wikipedia.org/wiki/CAP_theorem )

There was a presentation up here a few months ago on how the guys at http://wordsquared.com/ used MongoDB; they basically made the choice since they knew it already, instead of using postgres with their great geo libraries. And that's fine. What's stupid is when people who know one or the other pretty well spend a lot of time learning about the other for a use case that's most likely not really necessary anyway, or their current choice could handle with tweaks.

Of course, once public CS starts moving forward into innovative big analytics rather than just managing big data storage (such as the theta-join paper I linked elsewhere on this page), things may start shifting in favor of one of the NoSQL systems and the above quote would be equally suitable when comparing the Hadoop ecosystem or Mongo with some fancy new relational DB.

[alnayyir]

I wish people would stop linking CAP theorem, as if it proves something about one database or the other.

It doesn't.

It expresses some useful things about trade-offs but they aren't necessarily binary properties and it doesn't say anything about the underlying data structures or features of a database.

> then a lot of people don't need all that scalability. (And if it did, you'd use Hadoop anyway. =P

Maybe, not necessarily.