Geographic searches are specified using a $DISTANCE function. As long as there is a multi-column Omnidex index containing the latitude and longitude, the $distance function will be automatically optimized.
The following are examples of several types of geographic searches that can be optimized using the $distance function.
select $distance(40.0, -105.0, 41.0, -106.0) distance from $omnidex;
select zip, $distance(40.0, -105.0, latitude, longitude) distance, latitude, longitude, from zipcodes where $distance(40.0, -105.0, latitude, longitude) < 10;
select state, zip, latitude, longitude from zipcodes where $distance(latitude, longitude, (select latitude, longitude from zipcodes where state = 'CO')) < 5;