# Filter results by the length of the nested objects returned, similar to min\_child

**URL:** <https://discuss.elastic.co/t/filter-results-by-the-length-of-the-nested-objects-returned-similar-to-min-child/243582>\
**Category:** Elasticsearch\
**Created:** [August 3, 2020, 1:33pm UTC](https://discuss.elastic.co/t/filter-results-by-the-length-of-the-nested-objects-returned-similar-to-min-child/243582 "2020-08-03T13:33:00Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![Dustin\_Silk](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/dustin_silk/32/48390_2.png) [@Dustin\_Silk](https://discuss.elastic.co/u/Dustin_Silk)\
**Post date:** [August 3, 2020, 1:33pm UTC](https://discuss.elastic.co/t/filter-results-by-the-length-of-the-nested-objects-returned-similar-to-min-child/243582/1 "2020-08-03T13:33:00Z")

</div>

I'm trying to filter my results based on the number of nested objects found for a document.  
I've tried using scores but I cant get scores to work with filters, and I've tried a script but can't get that working either.

Below are more details on all of it. Basically I need to:

- Filter the parent documents by their properties
- Filter each nested object by a few properties
- Finally, filter the parent document by the number of nested documents remaining to a single fixed number

**These are my mappings:**

```auto
    "mappings": {
      "properties": {
        "dates" : {
          "type" : "nested",
          "properties" : {
            "rooms" : {
              "type" : "integer"
            },
            "timestamp" : {
              "type" : "long"
            }
          }
        },
        "doc_id" : {
          "type" : "text"
        },
        "distance" : {
          "type" : "integer"
        }
        ...
      }
    }

```

**Example data**

```auto
    PUT /test/_doc/1
    {
      "doc_id": "1",
      "distance": 1,
      "dates": [
        {
          "rooms": 1,
          "timestamp": 1
        },
        {
          "rooms": 1,
          "timestamp": 2
        },
        ...
      ]
    }

```

There are unknown number of nested dates, but won't be more than ~15 per document. I'm filtering by parent and nested child values.

**My attempt using a script:**

```auto
    GET /test/_search
    {
      "query": {
        "bool" : {
          "filter": [
            { "range": { "distance": { "lt": 5 }}},
            {
              "nested": {
                "path": "dates",
                "query": {
                  "bool": {
                    "filter": [
                      { "range": { "dates.rooms": { "gte": 1 } } },
                      { "range": { "dates.timestamp": { "lte": 2 }}},
                      { "range": { "dates.timestamp": { "gte": 1 }}}
                    ]
                  }
                }
              }
            },
            {
              "script": {
                "script": {
                  "source": "doc['dates'].length = 2",
                  "lang": "painless"
                }
              }
            }
          ]
        }
      }
    }

```

This throws an error: `No field found for [dates] in mapping with types []`

So I've tried to follow this solution [here](https://gist.github.com/xethorn/290e31176f493814823a20f281e82fd4)

**Attempt using scoring**

```auto
    GET /test/_search
    {
      "query" : {
        "function_score": {
          "min_score": 20,
          "boost": 1,
          "functions": [
            {
              "script_score": {
                "script": {
                    "source": "if (_score > 20) { return - 1; } return _score;"
                }
              }
            }
          ],
          "query": {
            "bool" : {
              "filter": [
                { "range": { "distance": { "lt": 5 }}},
                {
                  "nested": {
                    "score_mode": "sum",
                    "boost": 10,
                    "path": "dates",
                    "query": {
                      "bool": {
                        "filter": [
                          { "range": { "dates.rooms": { "gte": 1 } } },
                          { "range": { "dates.timestamp": { "lte": 2 }}},
                          { "range": { "dates.timestamp": { "gte": 1 }}}
                        ]
                      }
                    }
                  }
                }
              ]
            }
          }
        }
      }
    }

```

But Scoring doesnt work with filters and I can't seem to get this working at all.  
Would really appreciate any help on this topic.

Thanks!

---

<div class="post-metadata">

**Author:** ![spinscale](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/spinscale/32/25011_2.png) [@spinscale](https://discuss.elastic.co/u/spinscale)\
**Post date:** [August 4, 2020, 9:48am UTC](https://discuss.elastic.co/t/filter-results-by-the-length-of-the-nested-objects-returned-similar-to-min-child/243582/2 "2020-08-04T09:48:55Z")

</div>

Hey,

how about storing the size of the array in an extra field when indexing, so that your query for the size of the array becomes a range query and will be much much faster than the script one?

--Alex

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<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:** [September 1, 2020, 9:48am UTC](https://discuss.elastic.co/t/filter-results-by-the-length-of-the-nested-objects-returned-similar-to-min-child/243582/3 "2020-09-01T09:48:56Z")

</div>

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