Column "distance" does not exist when using Model.where about geokit-rails3 HOT 2 OPEN

As far as I understand, this is a SQL issue. Basically, you cannot filter (WHERE / HAVING) by calculated columns, so you cannot say SELECT foo.*, some_math() AS distance FROM foo WHERE distance < 5; but you can say SELECT foo.*, some_math() AS distance FROM foo WHERE some_math() < 5. Also, ordering by calculated columns is allowed.

So, one possible solution would be to repeat the distance calculation mathematics in the WHERE clause. Of course, this calls for a stored procedure of some kind, otherwise the generated SQL will be rather messy.

Another alternative (when you don't have millions of rows) is to filter by Ruby after the fact using find { |x| x.distance < 10 } or something like that. But this is not useable in a scope, so it's more like a hack.

from geokit-rails3.

Another way of doing this would be something like
Model.geo_scope(:within => foo, :origin => whatever).where("bar.radius > #{Model.sphere_distance_sql(...)} AND ...").
That way, you are duplicating the complicated spherical math in the SQL request, but apart from possible(!) bad performance this should not hurt.

from geokit-rails3.