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PODjango Sort By Calculated Field
 

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    <p>Using the distance logic from <a href="https://stackoverflow.com/questions/1916953/filter-zipcodes-by-proximity-in-django-with-the-haversine-formula">this SO post</a>, I'm getting back a properly-filtered set of objects with this code:</p> <pre><code>class LocationManager(models.Manager): def nearby_locations(self, latitude, longitude, radius, max_results=100, use_miles=True): if use_miles: distance_unit = 3959 else: distance_unit = 6371 from django.db import connection, transaction cursor = connection.cursor() sql = """SELECT id, (%f * acos( cos( radians(%f) ) * cos( radians( latitude ) ) * cos( radians( longitude ) - radians(%f) ) + sin( radians(%f) ) * sin( radians( latitude ) ) ) ) AS distance FROM locations_location HAVING distance &lt; %d ORDER BY distance LIMIT 0 , %d;""" % (distance_unit, latitude, longitude, latitude, int(radius), max_results) cursor.execute(sql) ids = [row[0] for row in cursor.fetchall()] return self.filter(id__in=ids) </code></pre> <p>The problem is I can't figure out how to keep the list/ queryset sorted by the distance value. I don't want to do this as an extra() method call for performance reasons (one query versus one query on each potential location in my database). A couple of questions:</p> <ol> <li>How can I sort my list by distance? Even taking off the native sort I've defined in my model and using "order_by()", it's still sorting by something else (id, I believe).</li> <li>Am I wrong about the performance thing and Django will optimize the query, so I should use extra() instead?</li> <li>Is this the totally wrong way to do this and I should use the geo library instead of hand-rolling this like a putz?</li> </ol>
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