Distance query snippet.

query snippet.py

# Get a query for all `Message`s.
query = Message.query

# Get the query parameters (in this example from a `request` object).
params = request.params
lat = params['latitude']
lng = params['longitude']
distance = params.get('distance', None)

# Generate the `within` clause to filter by, either using a `distance`
# provided, or by working it out using our `get_distance` class method.
if not distance:
    distance = Message.get_distance(query, lat, lng)
within = Message.within(lat, lng, distance)

# Filter by the `within` clause.
query = query.filter(within)

# Sort the results so the most recent come first.
query = query.order_by(Message.created.desc())