I've got a better solution than geohashing.
I break down the grid into sub-degree squares by truncating after the
first decimal point, and then when I save something that I need to
find on the map later, I save metadata with that point indicating the
surrounding grid squares.
So if I have a point with long -122.123123123 and lat 35.56565, that's
in a grid square called -122.1x35.5, and it's surrounded as follows:
[-122.2x35.6][-122.1x35.6][-122.0x35.6]
[-122.2x35.5][-122.1x35.5][-122.0x35.5]
[-122.2x35.4][-122.1x35.4][-122.0x35.4]
Those are all represented in my object as a list
(db.StringListProperty, so you have to do the right permutations to
make them into strings), and because of the way lists work, if a point
that you're searching on is in any of the grid squares associated with
a saved point, that saved point will come up.
To wit, if you have saved that above point, and someone comes in
searching on an address that corresponds to LONG -122.0857 LAT
35.69999, that corresponds to grid square '-122.0x35.6', which is in
your upper right hand corner. Thus, if you search for something like:
square = '-122.0x35.6'
points = (SELECT * FROM Locations WHERE gridList=:1", square)
...you'll find that the original point we saved above will return.
It's all about metadata. Don't think in terms of inequalities and
boundary conditions, think in terms of inclusive ranges.
Best,
Ben
On Jul 17, 2:26 pm, Nevin Freeman <[EMAIL PROTECTED]> wrote:
> I'm trying to figure out how to incorporate a filter based on the
> longitude attribute of an Entity's db.GeoPt property. I want to do
> something like this:
>
> GeoDataObj_query = GeoDataObj.gql("WHERE latlng.lat < :1 AND
> latlng.lat > :2 AND latlng.lon < :3 AND latlng.lon > :4"
> ,
> maxLat, minLat, maxLng, minLng)
>
> latlng is my db.GeoPt property, and you can't just do latlng.lat or
> latlng.lon. How do I access that longitude attribute, and can I do it
> within the bounds of the rule that limits inequality filters to a
> single property?
>
> Thanks,
> Nevin
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