Elastic Search Geo Spatial search implementation - elasticsearch

Question

I am trying to understand how elastic search supports Geo Spatial search internally.
For the basic search, it uses the inverted index; but how does it combine with the additional search criteria like searching for a particular text within a certain radius.
I would like to understand the internals of how the index would be stored and queried to support these queries

Answer 1

Text & geo queries are executed separately of one another. Let's take a concrete example:
PUT restaurants
{
"mappings": {
"properties": {
"location": {
"type": "geo_point"
},
"menu": {
"type": "text",
"fields": {
"keyword": {
"type": "keyword"
}
}
}
}
}
}
POST restaurants/_doc
{
"name": "rest1",
"location": {
"lat": 40.739812,
"lon": -74.006201
},
"menu": [
"european",
"french",
"pizza"
]
}
POST restaurants/_doc
{
"name": "rest2",
"location": {
"lat": 40.7403963,
"lon": -73.9950026
},
"menu": [
"pizza",
"kebab"
]
}
You'd then match a text field and apply a geo_distance filter:
GET restaurants/_search
{
"query": {
"bool": {
"must": [
{
"match": {
"menu": "pizza"
}
},
{
"geo_distance": {
"distance": "0.5mi",
"location": {
"lat": 40.7388,
"lon": -73.9982
}
}
},
{
"function_score": {
"query": {
"match_all": {}
},
"boost_mode": "avg",
"functions": [
{
"gauss": {
"location": {
"origin": {
"lat": 40.7388,
"lon": -73.9982
},
"scale": "0.5mi"
}
}
}
]
}
}
]
}
}
}
Since the geo_distance query only assigns a boolean value (--> score=1; only checking if the location is within a given radius), you may want to apply a gaussian function_score to boost the locations that are closer to a given origin.
Finally, these scores are overridable by using a _geo_distance sort where you'd order by the proximity (while of course keeping the match query intact):
...
"query: {...},
"sort": [
{
"_geo_distance": {
"location": {
"lat": 40.7388,
"lon": -73.9982
},
"order": "asc"
}
}
]
}