Update Handler: unique property

[Anthony Ananich]

Hi!

I have a database of documents like that:
{
    "_id" : "37686beb8d65e74665af55e69801a62c",
    "ip"  : "192.168.1.1",
    "mac" : "01:23:45:67:89:ab"
}
And I have a design doc with update handler. How can I check if a new
document have an unique mac address? Is it possible in CouchDB? If no,
than do any walkarounds  exist?

Thanks!
Anthony