[[search-facets-geo-distance-facet]]
=== Geo Distance Facets

The geo_distance facet is a facet providing information for ranges of
distances from a provided geo_point including count of the number of
hits that fall within each range, and aggregation information (like
total).

Assuming the following sample doc:

[source,js]
--------------------------------------------------
{
    "pin" : {
        "location" : {
            "lat" : 40.12,
            "lon" : -71.34
        }
    }
}
--------------------------------------------------

Here is an example that create a `geo_distance` facet from a
`pin.location` of 40,-70, and a set of ranges:

[source,js]
--------------------------------------------------
{
    "query" : {
        "match_all" : {}
    },
    "facets" : {
        "geo1" : {
            "geo_distance" : {
                "pin.location" : {
                    "lat" : 40,
                    "lon" : -70
                },
                "ranges" : [
                    { "to" : 10 },
                    { "from" : 10, "to" : 20 },
                    { "from" : 20, "to" : 100 },
                    { "from" : 100 }
                ]
            }
        }
    }
}
--------------------------------------------------

==== Accepted Formats

In much the same way the geo_point type can accept different
representation of the geo point, the filter can accept it as well:

===== Lat Lon As Properties

[source,js]
--------------------------------------------------
{
    "query" : {
        "match_all" : {}
    },
    "facets" : {
        "geo1" : {
            "geo_distance" : {
                "pin.location" : {
                    "lat" : 40,
                    "lon" : -70
                },
                "ranges" : [
                    { "to" : 10 },
                    { "from" : 10, "to" : 20 },
                    { "from" : 20, "to" : 100 },
                    { "from" : 100 }
                ]
            }
        }
    }
}
--------------------------------------------------

===== Lat Lon As Array

Format in `[lon, lat]`, note, the order of lon/lat here in order to
conform with http://geojson.org/[GeoJSON].

[source,js]
--------------------------------------------------
{
    "query" : {
        "match_all" : {}
    },
    "facets" : {
        "geo1" : {
            "geo_distance" : {
                "pin.location" : [40, -70],
                "ranges" : [
                    { "to" : 10 },
                    { "from" : 10, "to" : 20 },
                    { "from" : 20, "to" : 100 },
                    { "from" : 100 }
                ]
            }
        }
    }
}
--------------------------------------------------

===== Lat Lon As String

Format in `lat,lon`.

[source,js]
--------------------------------------------------
{
    "query" : {
        "match_all" : {}
    },
    "facets" : {
        "geo1" : {
            "geo_distance" : {
                "pin.location" : "40, -70",
                "ranges" : [
                    { "to" : 10 },
                    { "from" : 10, "to" : 20 },
                    { "from" : 20, "to" : 100 },
                    { "from" : 100 }
                ]
            }
        }
    }
}
--------------------------------------------------

===== Geohash

[source,js]
--------------------------------------------------
{
    "query" : {
        "match_all" : {}
    },
    "facets" : {
        "geo1" : {
            "geo_distance" : {
                "pin.location" : "drm3btev3e86",
                "ranges" : [
                    { "to" : 10 },
                    { "from" : 10, "to" : 20 },
                    { "from" : 20, "to" : 100 },
                    { "from" : 100 }
                ]
            }
        }
    }
}
--------------------------------------------------

==== Ranges

When a `to` or `from` are not set, they are assumed to be unbounded.
Ranges are allowed to overlap, basically, each range is treated by
itself.

==== Options

[cols="<,<",options="header",]
|=======================================================================
|Option |Description
|`unit` |The unit the ranges are provided in. Defaults to `km`. Can also
be `mi` or `miles`.

|`distance_type` |How to compute the distance. Can either be `arc`
(better precision) or `plane` (faster). Defaults to `arc`.
|=======================================================================

==== Value Options

On top of the count of hits falling within each range, aggregated data
can be provided (total) as well. By default, the aggregated data will
simply use the distance calculated, but the value can be extracted
either using a different numeric field, or a script. Here is an example
of using a different numeric field:

[source,js]
--------------------------------------------------
{
    "query" : {
        "match_all" : {}
    },
    "facets" : {
        "geo1" : {
            "geo_distance" : {
                "pin.location" : "drm3btev3e86",
                "value_field" : "num1",
                "ranges" : [
                    { "to" : 10 },
                    { "from" : 10, "to" : 20 },
                    { "from" : 20, "to" : 100 },
                    { "from" : 100 }
                ]
            }
        }
    }
}
--------------------------------------------------

And here is an example of using a script:

[source,js]
--------------------------------------------------
{
    "query" : {
        "match_all" : {}
    },
    "facets" : {
        "geo1" : {
            "geo_distance" : {
                "pin.location" : "drm3btev3e86",
                "value_script" : "doc['num1'].value * factor",
                "params" : {
                    "factor" : 5
                }
                "ranges" : [
                    { "to" : 10 },
                    { "from" : 10, "to" : 20 },
                    { "from" : 20, "to" : 100 },
                    { "from" : 100 }
                ]
            }
        }
    }
}
--------------------------------------------------

Note the params option, allowing to pass parameters to the script
(resulting in faster script execution instead of providing the values
within the script each time).

.`geo_point` Type
[NOTE]
--
The facet *requires* the `geo_point` type to be set on the relevant
field.
--

.Multi Location Per Document
[NOTE]
--
The facet can work with multiple locations per document.
--