Find all by distance from a reference point

In my Grails 1.3.7 application, I have a Building entity with a Double latitude and a Double longitude. I'm implementing a simple search engine in order to find all the Building instances with a given distance of the point where the user is (latitude and longitude in decimal degrees). I found this http://www.scribd.com/doc/2569355/Geo-Distance-Search-with-MySQL which is good because I'm using a MySQL database. And the bounding box approximation is excellent for me as I need to perform additional filtering and calculations and I just need a finder that narrows down the number of instances I'm filtering. My question is: has anybody already implemen开发者_如何学Cted this kind of search in a Grails environment and how?

I have implemented something with similar requirements before, and I used a HQL query. It was a while ago and I remember it took me quite a while to read up and figure out, so hopefully saves you some time.

This does a select based on a current location (a simple lat long container object), and a "name" (startswith). It selects the domain object (venue) and also the miles away from the current location. It sorts by miles away ascending. Note I added a "road factor" fudge to approximate road distances.

def getVenuesInArea(venueName, location, miles, optionsMap)
{
    def max = optionsMap?.max ?: 10
    def offset = optionsMap?.offset ?: 0
    if (venueName == null) venueName = "" 
    venueName += '%'

    double roadFactor = 1.20 // add 20% for the roads, instead of as crow flies...

    def query
    def results

    def countQuery = """ select count( distinct v)

                from Venue as v
                WHERE
                v.name like :venueName AND
                ( acos
                    (
                        sin(radians(:lat))
                        * sin(radians(v.location.latitude))
                        + cos(radians(:lat))
                        * cos(radians(v.location.latitude))
                        * cos(radians(v.location.longitude) - radians(:lon))
                    ) * 3956.1676 * :roadFactor < :distance
                )

            """

    def count = Venue.executeQuery(countQuery, [venueName:venueName, lat:location.latitude, lon:location.longitude, distance:miles, roadFactor:roadFactor])[0]

    query = """ select distinct v,

                (
                    acos
                    (
                        sin(radians(:lat))
                        * sin(radians(v.location.latitude))
                        + cos(radians(:lat))
                        * cos(radians(v.location.latitude))
                        * cos(radians(v.location.longitude) - radians(:lon))
                    )
                    * 3956.1676 * :roadFactor
                ) as milesAway

                from Venue as v
                WHERE
                v.name like :venueName AND
                ( acos
                    (
                        sin(radians(:lat))
                        * sin(radians(v.location.latitude))
                        + cos(radians(:lat))
                        * cos(radians(v.location.latitude))
                        * cos(radians(v.location.longitude) - radians(:lon))
                    ) * 3956.1676 * :roadFactor < :distance
                )

                order by
                (
                    acos
                    (
                        sin(radians(:lat))
                        * sin(radians(v.location.latitude))
                        + cos(radians(:lat))
                        * cos(radians(v.location.latitude))
                        * cos(radians(v.location.longitude) - radians(:lon))
                    )
                    * 3956.1676 * :roadFactor
                )
                asc,
                v.name

            """

    results = Venue.executeQuery( query, [venueName:venueName, lat:location.latitude, lon:location.longitude, distance:miles, roadFactor:roadFactor, max:max, offset:offset])

    def venues = []
    MathContext mc = new MathContext(2)
    results.each
    { result ->
        VenueWithDetails venueDetails = new VenueWithDetails(  venue:result[0], milesFrom:new BigDecimal(result[1]).round(mc)  )
        venues.add(venueDetails)
    }
    return [venues:venues, count:count]
}

This was done on grails version 1.3.4, but pretty sure it should work fine for 1.3.7.

Hope that helps, Chris.