ElasticSearch aggregation query with List in documents - elasticsearch

Question

I have following records of car sales of different brands in different cities.
Document -1
{
"city": "Delhi",
"cars":[{
"name":"Toyota",
"purchase":100,
"sold":80
},{
"name":"Honda",
"purchase":200,
"sold":150
}]
}
Document -2
{
"city": "Delhi",
"cars":[{
"name":"Toyota",
"purchase":50,
"sold":40
},{
"name":"Honda",
"purchase":150,
"sold":120
}]
}
I am trying to come up with query to aggregate car statistics for a given city but not getting the right query.
Required result:
{
"city": "Delhi",
"cars":[{
"name":"Toyota",
"purchase":150,
"sold":120
},{
"name":"Honda",
"purchase":350,
"sold":270
}]
}

Answer 1

First you need to map your array as a nested field (script would be complicated and not performant). Nested field are indexed, aggregation will be pretty fast.
remove your index / or create a new one. Please note i use test as type.
{
"mappings": {
"test": {
"properties": {
"city": {
"type": "keyword"
},
"cars": {
"type": "nested",
"properties": {
"name": {
"type": "keyword"
},
"purchase": {
"type": "integer"
},
"sold": {
"type": "integer"
}
}
}
}
}
}
}
Index your document (same way you did)
For the aggregation:
{
"size": 0,
"aggs": {
"avg_grade": {
"terms": {
"field": "city"
},
"aggs": {
"resellers": {
"nested": {
"path": "cars"
},
"aggs": {
"agg_name": {
"terms": {
"field": "cars.name"
},
"aggs": {
"avg_pur": {
"sum": {
"field": "cars.purchase"
}
},
"avg_sold": {
"sum": {
"field": "cars.sold"
}
}
}
}
}
}
}
}
}
}
result:
buckets": [
{
"key": "Honda",
"doc_count": 2,
"avg_pur": {
"value": 350
},
"avg_sold": {
"value": 270
}
}
,
{
"key": "Toyota",
"doc_count": 2,
"avg_pur": {
"value": 150
},
"avg_sold": {
"value": 120
}
}
]
if you have index the name / city field as a text (you have to ask first if this is necessary), use .keyword in the term aggregation ("cars.name.keyword").