32_Bounding_box.asciidoc

Geo Bounding Box Filter

This is by far the most efficient geo-filter because its calculation is very simple. You provide it with the top, bottom, left, and right coordinates of a rectangle, and all it does is compare the longitude with the left and right coordinates, and the latitude with the top and bottom coordinates:

GET /attractions/restaurant/_search
{
  "query": {
    "filtered": {
      "filter": {
        "geo_bounding_box": {
          "location": { (1)
            "top_left": {
              "lat":  40.8,
              "lon": -74.0
            },
            "bottom_right": {
              "lat":  40.7,
              "lon": -73.0
            }
          }
        }
      }
    }
  }
}

1. These coordinates can also be specified as bottom_left and top_right.

Optimizing Bounding Boxes

The geo_bounding_box is the one geo-filter that doesn’t require all geo-points to be loaded into memory. Because all it has to do is check whether the lat and lon values fall within the specified ranges, it can use the inverted index to do a glorified range filter.

To use this optimization, the geo_point field must be mapped to index the lat and lon values separately:

PUT /attractions
{
  "mappings": {
    "restaurant": {
      "properties": {
        "name": {
          "type": "string"
        },
        "location": {
          "type":    "geo_point",
          "lat_lon": true (1)
        }
      }
    }
  }
}

1. The location.lat and location.lon fields will be indexed separately. These fields can be used for searching, but their values cannot be retrieved.

Now, when we run our query, we have to tell Elasticsearch to use the indexed lat and lon values:

GET /attractions/restaurant/_search
{
  "query": {
    "filtered": {
      "filter": {
        "geo_bounding_box": {
          "type":    "indexed", (1)
          "location": {
            "top_left": {
              "lat":  40.8,
              "lon": -74.0
            },
            "bottom_right": {
              "lat":  40.7,
              "lon":  -73.0
            }
          }
        }
      }
    }
  }
}

1. Setting the type parameter to indexed (instead of the default memory) tells Elasticsearch to use the inverted index for this filter.

Caution

While a geo_point field can contain multiple geo-points, the lat_lon optimization can be used only on fields that contain a single geo-point.