How to do two nested aggregations in elasticsearch? - elasticsearch

Question

City and home type are two nested objects in the following document mapping:
"mappings" : {
"home_index_doc" : {
"properties" : {
"city" : {
"type" : "nested",
"properties" : {
"country" : {
"type" : "nested",
"properties" : {
"name" : {
"type" : "text"
}
}
},
"name" : {
"type" : "keyword"
}
}
},
"home_type" : {
"type" : "nested",
"properties" : {
"name" : {
"type" : "keyword"
}
}
},
...
}
}
}
I am trying to do the following aggregation:
Take all present documents and show all home_types per city.
I imagine it should look similar to:
"aggregations": {
"all_cities": {
"buckets": [
{
"key": "Tokyo",
"doc_count": 12,
"home_types": {
"buckets": [
{
"key": "apartment",
"doc_count": 5
},
{
"key": "house",
"doc_count": 12
}
]
}
},
{
"key": "New York",
"doc_count": 1,
"home_types": {
"buckets": [
{
"key": "house",
"doc_count": 1
}
]
}
}
]
}
}
After trying gazzilion aproaches and combinations, I've made it that far with Kibana:
GET home-index/home_index_doc/_search
{
"size": 0,
"aggs": {
"all_cities": {
"nested": {
"path": "city"
},
"aggs": {
"city_name": {
"terms": {
"field": "city.name"
}
}
}
},
"aggs": {
"all_home_types": {
"nested": {
"path": "home_type"
},
"aggs": {
"home_type_name": {
"terms": {
"field": "home_type.name"
}
}
}
}
}
}
}
and I get the following exception:
"type": "unknown_named_object_exception",
"reason": "Unknown BaseAggregationBuilder [all_home_types]",

Answer 1

You need to use reverse_nested in order to jump out of the city nested type back at the root level and do another nested aggregation for the home_type nested type. Basically, like this:
{
"size": 0,
"aggs": {
"all_cities": {
"nested": {
"path": "city"
},
"aggs": {
"city_name": {
"terms": {
"field": "city.name"
},
"aggs": {
"by_home_types": {
"reverse_nested": {},
"aggs": {
"all_home_types": {
"nested": {
"path": "home_type"
},
"aggs": {
"home_type_name": {
"terms": {
"field": "home_type.name"
}
}
}
}
}
}
}
}
}
}
}
}