ElasticSearch Max Agg on lowest value inside a list property of the document - elasticsearch

Question

I'm looking to do a Max aggregation on a value of the property under my document, the property is a list of complex object (key and value). Here's my data:
[{
"id" : "1",
"listItems" :
[
{
"key" : "li1",
"value" : 100
},
{
"key" : "li2",
"value" : 5000
}
]
},
{
"id" : "2",
"listItems" :
[
{
"key" : "li3",
"value" : 200
},
{
"key" : "li2",
"value" : 2000
}
]
}]
When I do the Nested Max Aggregation on "listItems.value", I'm expecting the max value returned to be 200 (and not 5000), reason being I want the logic to first figure the MIN value under listItems for each document, then doing the Max Aggregation on that. Is it possible to do something like this?
Thanks.

Answer 1

The search query performs the following aggregation :
Terms aggregation on the id field
Min aggregation on listItems.value
Max bucket aggregation that is a sibling pipeline aggregation which identifies the bucket(s) with the maximum value of a specified metric in a sibling aggregation and outputs both the value and the key(s) of the bucket(s).
Please refer to nested aggregation, to get a detailed explanation on it.
Adding a working example with index data, index mapping, search query, and search result.
Index Mapping:
{
"mappings": {
"properties": {
"listItems": {
"type": "nested"
},
"id":{
"type":"text",
"fielddata":"true"
}
}
}
}
Index Data:
{
"id" : "1",
"listItems" :
[
{
"key" : "li1",
"value" : 100
},
{
"key" : "li2",
"value" : 5000
}
]
}
{
"id" : "2",
"listItems" :
[
{
"key" : "li3",
"value" : 200
},
{
"key" : "li2",
"value" : 2000
}
]
}
Search Query:
{
"size": 0,
"aggs": {
"id_terms": {
"terms": {
"field": "id"
},
"aggs": {
"nested_entries": {
"nested": {
"path": "listItems"
},
"aggs": {
"min_position": {
"min": {
"field": "listItems.value"
}
}
}
}
}
},
"maxValue": {
"max_bucket": {
"buckets_path": "id_terms>nested_entries>min_position"
}
}
}
}
Search Result:
"aggregations": {
"id_terms": {
"doc_count_error_upper_bound": 0,
"sum_other_doc_count": 0,
"buckets": [
{
"key": "1",
"doc_count": 1,
"nested_entries": {
"doc_count": 2,
"min_position": {
"value": 100.0
}
}
},
{
"key": "2",
"doc_count": 1,
"nested_entries": {
"doc_count": 2,
"min_position": {
"value": 200.0
}
}
}
]
},
"maxValue": {
"value": 200.0,
"keys": [
"2"
]
}
}

Answer 2

Initial post was mentioning nested aggregation, thus i was sure question is about nested documents. Since i've come to solution before seeing another answer, i'm keeping the whole thing for history, but actually it differs only in adding nested aggregation.
The whole process can be explained like that:
Bucket each document into single bucket.
Use nested aggregation to be able to aggregate on nested documents.
Use min aggregation to find minimum value within all document nested documents, and by that, for document itself.
Finally, use another aggregation to calculate maximum value among results of previous aggregation.
Given this setup:
// PUT /index
{
"mappings": {
"properties": {
"children": {
"type": "nested",
"properties": {
"value": {
"type": "integer"
}
}
}
}
}
}
// POST /index/_doc
{
"children": [
{ "value": 12 },
{ "value": 45 }
]
}
// POST /index/_doc
{
"children": [
{ "value": 7 },
{ "value": 35 }
]
}
I can use those aggregations in request to get required value:
{
"size": 0,
"aggs": {
"document": {
"terms": {"field": "_id"},
"aggs": {
"children": {
"nested": {
"path": "children"
},
"aggs": {
"minimum": {
"min": {
"field": "children.value"
}
}
}
}
}
},
"result": {
"max_bucket": {
"buckets_path": "document>children>minimum"
}
}
}
}
{
"aggregations": {
"document": {
"doc_count_error_upper_bound": 0,
"sum_other_doc_count": 0,
"buckets": [
{
"key": "O4QxyHQBK5VO9CW5xJGl",
"doc_count": 1,
"children": {
"doc_count": 2,
"minimum": {
"value": 7.0
}
}
},
{
"key": "OoQxyHQBK5VO9CW5kpEc",
"doc_count": 1,
"children": {
"doc_count": 2,
"minimum": {
"value": 12.0
}
}
}
]
},
"result": {
"value": 12.0,
"keys": [
"OoQxyHQBK5VO9CW5kpEc"
]
}
}
}
There also should be a workaround using script for calculating max - all that you will need to do is just find and return smallest value in document in such script.