geo_near

Determines geospatial objects in proximity to a point.

boolean geo_near(any*, any*, double)

The first and the second parameters any* can be any geometric object.

The function determines if the first geometry is within a distance of N meters from the second geometry.

If any of the two parameters does not return a single valid geometry object, and if it can be detected at compile time then the function raises an error.

The runtime behavior is as follows:

• Returns false if any parameter returns 0 or more than 1 item.

• Returns NULL if any of the first two parameters returns NULL.

• Returns false if any of the first two parameters returns an item that is not a valid geometry object.

Finally, if both of the first two parameters return a single geometry object each, it returns true if the first geometry is within a distance of N meters from the second geometry, where N is the number returned by the third parameter; otherwise false.

Note: geo_near is converted internally to geo_within_distance plus an (implicit) order by the distance between the two geometries. However, if the query has an (explicit) order-by already, no ordering by distance is performed. The geo_near function can appear in the WHERE clause only, where it must be a top-level predicate, i.e, not nested under an OR or NOT operator.

Example 1 - Is there a hospital within 3km of the given location?

SELECT
t.poi.name AS hospital_name,
t.poi.address.street AS hospital_address
FROM PointsOfInterest t
WHERE t.poi.kind = "hospital"
AND
geo_near(
    t.poi.location,
    {"type" : "point",
     "coordinates" : [-122.03493933105469,37.32949164059004]
    },
    3000
);

Explanation:

• You query the PointsOfInterest table to filter the rows for hospital.

• You use the geo_near function to filter hospitals within 3000m of the given location.

Result:

{"hospital_name":"St. Marthas hospital","hospital_address":"18000 West Blvd"}
{"hospital_name":"Memorial hospital","hospital_address":"10500 South St"}

Example 2 - How far is a gas station within the next one mile from the given location?

SELECT
t.poi.address.street AS gas_station_address,
geo_distance(
    t.poi.location,
    {
        "type" : "point",
        "coordinates" : [-121.90768646240233,37.292081740702365]
    }
) AS distance_in_meters
FROM PointsOfInterest t
WHERE t.poi.kind = "gas station" AND
geo_near(
    t.poi.location,
    {
        "type" : "point",
        "coordinates" : [-121.90768646240233,37.292081740702365]
    },
    1600
);

Explanation:

• You query the PointsOfInterest table to filter the rows for gas station.

• You use the geo_near function to filter gas stations within one mile(1600m) of the given location.

• You also fetch the actual distance between your location and the gas station using the geo_distance function.

Result:

{"gas_station_address":"33 North Avenue","distance_in_meters":886.7004173859665}

The actual distance to the nearest gas station within the next mile is 886m.