Flutterby™! : OS/X: Glad to be clear of it

Mark Atwood has some musings on MySQL User Defined Aggregate Functions, in which, 12 hours before he was supposed to give a talk on how to use them to speed up processing, he discovered that they're 3x slower than built-ins.

But the addendum is:

It turns out to be a MacOS thing. On Linux, the performance penalty is less than 10%. Further research will surely be done.

Yep, that's my experience. Those proprietary OSs will kick your butt when you least expect it.