[blueberry]

who uses MySQL as anything but a glorified key-value store when reaching large sizes?

My assumption is both Quora and Facebook use MySQL this way. While you are right that this is not using it as a real database, I want to know if PostgreSQL is deployed in a similar setup at all. Most of the people (including you) don't take into account the fact that there are many cases where MySQL (used as a KV store) proved to work, while I have never heard of such huge PostgreSQL deployments. If this was a general discussion regarding MySQL and PostgreSQL I could understand that, however, I think the post is more about whether to choose MySQL or PostgreSQL if you are going to use it as a KV store.

[petrilli]

The introduction of hstore actually lets you do this natively. I think it's partially that PostgreSQL people tend not to try and use the hammer as a screw driver, but maybe that's just me.

Or maybe sometimes MySQL is a screw driver being used as a hammer?