Elasticsearch query to process log data - elasticsearch

Question

I have an event log of an e-commerce website in Elasticsearch.
Each event is a record in ES
{
"_index": "event_log",
"_type": "log_type",
"_id": "3ud-kmoBazYRVz7KCgIy",
"_score": 1,
"_source": {
"user_id": 123,
"event": "click",
"category": "abc",
"product_id": 1112
}
},
{
"_index": "event_log",
"_type": "log_type",
"_id": "4Od-kmoBazYRVz7KCgLr",
"_score": 1,
"_source": {
"user_id": 123,
"event": "click",
"category": "abc",
"product_id": 1118
}
},
{
"_index": "event_log",
"_type": "log_type",
"_id": "4ud-kmoBazYRVz7KkwL2",
"_score": 1,
"_source": {
"user_id": 123,
"event": "cart",
"category": "xyz",
"product_id": 1
}
},
{
"_index": "event_log",
"_type": "log_type",
"_id": "2ud-kmoBazYRVz7KCALB",
"_score": 1,
"_source": {
"user_id": 123,
"event": "cart",
"category": "xyz",
"product_id": 11
}
},
I want list of all the product_ids grouping event, category, user.
Expected output:
{"click": {
"abc": {
"123": {
"product_id": [1112, 1118]
}
}
},
"cart": {
"xyz": {
"123": {
"product_id": [1, 11]
}
}
}
}
I will be having millions of records in the index. Querying all the records and processing it is time-consuming. Is there a way to produce the output in a single query? I'm sure it is not possible to generate exactly in the given format. Something near to it is very useful.

Answer 1

Hi here is my suggestion (first try)
GET event_log/_search
{
"size": 0,
"aggs": {
"event": {
"terms": {
"field": "event"
},
"aggs": {
"category": {
"terms": {
"field": "category"
},
"aggs": {
"product_id": {
"terms": {
"field": "product_id"
}
}
}
}
}
}
}
}