# Aggregation on specific values of nested fields per document

**URL:** <https://discuss.elastic.co/t/aggregation-on-specific-values-of-nested-fields-per-document/156031>\
**Category:** Elasticsearch\
**Created:** [November 9, 2018, 11:08am UTC](https://discuss.elastic.co/t/aggregation-on-specific-values-of-nested-fields-per-document/156031 "2018-11-09T11:08:31Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![jaip.1631](https://avatars.discourse-cdn.com/v4/letter/j/f04885/32.png) [@jaip.1631](https://discuss.elastic.co/u/jaip.1631)\
**Post date:** [November 9, 2018, 11:08am UTC](https://discuss.elastic.co/t/aggregation-on-specific-values-of-nested-fields-per-document/156031/1 "2018-11-09T11:08:31Z")

</div>

Is there some way to get stats aggergation on nested fields such that I only consider maximum of specific values of nested fields for the stats evaluation.

**Mapping:**

```
{
    "mappings": {
        "doc": {
            "properties": {
                "student_id": {
                    "type": "long"
                },
                "test_scores": {
                    "type": "nested",
                    "properties": {
                        "test_id": {
                            "type": "long"
                        },
                        "score": {
                            "type": "double"
                        }
                    }
                } 
            }
        }
    }
}

```

**Sample Data:**

```
{
  "student_id": 1,
  "test_scores": [
    {
      "test_id": 101,
      "score": 90
    },
    {
      "test_id": 102,
      "score": 70
    },
    {
      "test_id": 103,
      "score": 80
    }
  ]
}

{
  "student_id": 2,
  "test_scores": [
    {
      "test_id": 101,
      "score": 80
    },
    {
      "test_id": 102,
      "score": 90
    },
    {
      "test_id": 103,
      "score": 85
    }
  ]
}

{
  "student_id": 3,
  "test_scores": [
    {
      "test_id": 101,
      "score": 30
    },
    {
      "test_id": 102,
      "score": 40
    },
    {
      "test_id": 103,
      "score": 55
    }
  ]
}

```

**Filtering Query:**

```
{
  "query": {
    "bool": {
      "should": [
        {
          "bool": {
            "must": [
              {
                "term": {
                  "student_id": 1
                }
              },
              {
                "nested": {
                  "path": "test_scores",
                  "query": {
                    "terms": {
                      "test_scores.test_id": [101] 
                    }
                  }
                }
              }
            ]
          }
        },
        {
          "bool": {
            "must": [
              {
                "term": {
                  "student_id": 2
                }
              },
              {
                "nested": {
                  "path": "test_scores",
                  "query": {
                    "terms": {
                      "test_scores.test_id": [101, 103] 
                    }
                  }
                }
              }
            ]
          }
        }
      ]
    }
  }
}

```

**Requirement:**

I need to find min and max (stats aggregation) on test\_scores.score for students based on the aboe filtering query such that I only consider maximum test\_scores.score per student\_id.

# Example:

From the filtered documents from above query,

```
doc: 
  student_id: 1
  test_scores.test_id: 101
  test_scores.score: 90
  test_scores.score (To be considered for aggregation): 90

doc:
  student_id: 2
  test_scores.test_id: 101, 103
  test_scores.score: 80, 85
  test_scores.score (To be considered for aggregation): 85

Expected overall stats on test_scores.score:
max: 90
min: 85

```

# Findings

**After searching on web, I found a solution:**

```
{
  "aggs": {
    "score_stats": { 
      "stats": {
        "script": "if(doc[\"student_id\"].value == 1){                      
                    return params._source[\"test_scores\"]                  
                        .stream()                                           
                        .filter(nested -> nested.test_id == 101)            
                        .mapToDouble(nested -> nested.score)                
                        .max()                                              
                        .orElse(0)                                          
                  } else if(doc[\"student_id\"].value == 2){                
                    return params._source[\"test_scores\"]                  
                        .stream()                                           
                        .filter(nested ->                                   
                            nested.test_id == 101 || nested.test_id == 103) 
                        .mapToDouble(nested -> nested.score)                
                        .max()                                              
                        .orElse(0)                                          
                  } else {                                                  
                    return 0                                                
                  }"          
      }
    }
  },
  "query": {
        //filtering query copied here
    }
  }
}

```

**Response:**

```
"aggregations" : {
  "score_stats" : {
    "count" : 2,
    "min" : 85.0,
    "max" : 90.0,
    "avg" : 87.5,
    "sum" : 175.0
  }
}

```

# **Problem:**

While this solution works for above simple query. My real queries can be quite complex. This approach is not scalable as there is an upper limit on script length.

I tried testing around nested aggregations with filtering aggregation but it seems that after going inside nested path, we can't perform AND/OR with nonNested fields.

Is there some better way to get stats aggergation on nested fields such that I only consider maximum of specific values of nested fields for the stats evaluation.

---

<div class="post-metadata">

**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\
**Post date:** [December 7, 2018, 11:08am UTC](https://discuss.elastic.co/t/aggregation-on-specific-values-of-nested-fields-per-document/156031/2 "2018-12-07T11:08:42Z")

</div>

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