I have been doing a lot of work of late connecting  Google App Engine, and in particular Google Wave with the Force.com platform. I have mentioned the importance and power of convergent platforms before, so I wont rehash that topic, instead I wanted to point out a feature on Force.com which I have briefly mentioned some time ago: Lookup Filters. Lookup Filters work, by filtering a search on a Lookup field (thus the name, Lookup Filter. 🙂 ). You can quickly visually see any fields that have filters enabled by looking for the little funnel icon:

 I had used lookup filters in the past with a single filter, something like this:

But for my current requirements, I needed to filter on more than one criteria. Luckily, Lookup Filters came to the rescue. I added my two criteria; in this scenario, the Google Wave address of a User could be either a 'person' (@googlewave.com), or a 'robot' (@appspot.com). 

The trick is to use the Advanced Filter Condition to combine filter rows. Being the typical techie, I jumped right in and started putting a formula expression in Advanced Filter Condition box. Don't make my mistake though. I should have taken a minute to click the help icon to learn how to use the Advanced Filter's. Like many things on the platform, the solution was easier than I thought. I had two filter criteria which I wanted to evaluate with an OR statement. The result was a formula like this:

Notice I have two criteria (#1 and #2). All I had to do was write a Advanced Filter Condition as logical as the name 'Lookup Filter': 1 OR 2

Problem solved. For now, however, it is time to get back to work.