CouchDB currently uses Spidermonkey 1.7 as it's javascript interpreter. 1.7 was released in 2007. 1.8.5 is the current version number used in trunk, anything 1.8.1 should have tracing support and should be much improved in terms of performance.
1.8.x also has a lot of new JavaScript features that would be incredibly useful in views (array comprehensions would be a godsend). Mozilla also has a native JSON parser written in C which is something like 2.7 times faster than eval. http://blog.mozilla.com/webdev/2009/02/12/native-json-in-firefox-31/ I'm wondering what barriers, if any, there are to increasing the required Spidermonkey version. I've also been told that there are some issues with using the C based JSON parser because of the way undefined is encoded in arrays and would like a little more clarity on what work would need to happen to get that in. My biggest concern is that as more view servers are implemented in other languages javascript becomes the "slow" option, which seems ridiculous given the performance leapfrogging in recent years between js interpreters. In my tests the biggest speed differential appears to be JSON parsing: http://www.mikealrogers.com/archives/673 -Mikeal
