Guys there's a semi-official database for just this question.
http://sougouwiki.com/
It's pure Japanese so a little hard to use for your civilians. But you don't have to know any Japanese to use it. Enter a video code in the search box and hit the button to the right, you get a few links back in the search results. Typical there are some (or just 1) actress pages and 1 or more video pages. Ignore the actress pages, find the video page and nav to it. A page may have up to 200 or even more vids on one page (yeah it's very old fashion web design), e.g. HUNTA-201~400. Do a "find in page" with your vid code and you will see the cover and some info, most useful being (almost) all actress names in the vid, including all the names missing from DMM.
Now it's not 100% foolproof. Some rather minor or new video series may not be covered, and some (SOD mostly) video series, it seems, hire real amateurs who really don't have a JAV name. But I bet it will satisfy 95+% of you "who's in that vid" questions.
Of course you can search by actress name and get all her vids (more comprehensive than almost any other website). But sometimes you get (newbie?) idol who doesn't have her own page on Sougouwiki yet. You can still find her from video id.
I actually wrote a semi-auto program to bulk-parse Sougouwiki table (with the 200 vids) and bulk-insert the actress name to my JAV database.