Elasticsearch hierarchical aggregations

steps.txt

DELETE sandbox
PUT sandbox
{
  "mappings": {
    "test-cat": {
      "properties": {
        "title": {
          "type": "string"
        },
        "categories": {
          "type": "object",
          "properties": {
            "children": {
              "type": "nested",
              "properties": {
                "children": {
                  "type": "nested",
                  "properties": {}
                },
                "name": {
                  "type": "string"
                }
              }
            },
            "name": {
              "index": "not_analyzed",
              "omit_norms": true,
              "type": "string"
            }
          }
        }
       }
    }
  }
}

GET /_all

DELETE /sandbox/test-cat/1
POST /sandbox/test-cat/1
{
    "title": "Item 1",
    "categories": [
        {
            "name": "A",
            "children": [
                {
                    "name": "A1"
                },
                {
                    "name": "A2"
                }]
        },
        {
            "name": "B",
            "children": [
                {
                    "name": "B1"
                }]
      }]
}

DELETE /sandbox/test-cat/2
POST /sandbox/test-cat/2
{
    "title": "Item 2",
    "categories": [
        {
            "name": "A",
            "children": [
                {
                    "name": "A1"
                }]
        }]
}

POST /sandbox/test-cat/_search?search_type=count
{
  "aggs": {
    "category": {
      "terms": {
        "field": "categories.name"
      },
      "aggs": {
          "nested_category" : {
              "nested" : {
                "path": "categories.children"
              },
              "aggs": {
                  "child_categories" : {
                      "terms": {
                          "field": "categories.children.name"
                      }
                  }
              }
          }
      }
    }
  },
  "query": {
    "filtered": {
      "query": {
        "match_all": {}
      }
    }
  }
}