You got me :). And not only is it a possibility, but actually a certainty, if you set your own settings and don't re-set them on every new connection. This is an issue with all frameworks that allow persistent connections. For example a while ago I was working on a Django app where I needed to have the timezone set to the user's timezone when talking to MySQL. This meant that on every request I'd have to re-send a query, setting the timezone even if it did nothing. Alternatively, if I relied on the default timezone being UTC, I still had to set it explicitly, because the prior request might not have cleaned up after itself properly.

In short, unless your database has a way of saying "reset all settings", you cannot have persistent connections in any environment.