How can I access an array item in elasticsearch script

Question

I have this mapping for my index:

    "my_index": {
        "mappings": {
            "properties": {
                "medias": {
                    "properties": {
                        "media_id": {
                            "type": "text",
                            "fields": {
                                "keyword": {
                                    "type": "keyword",
                                    "ignore_above": 256
                                }
                            }
                        },
                        "media_type": {
                            "type": "long"
                        },
                        "variant": {
                            "properties": {
                                "height": {
                                    "type": "long"
                                },
                                "url": {
                                    "type": "text",
                                    "fields": {
                                        "keyword": {
                                            "type": "keyword",
                                            "ignore_above": 256
                                        }
                                    }
                                },
                                "width": {
                                    "type": "long"
                                }
                            }
                        },
                        "view_count": {
                            "type": "long"
                        }
                    }
                }
              
}

And I want to write a script for custom scoring like this:

    // "_source": "content",
    "query": {
        "function_score": {
            "functions": [
                {
                    "script_score": {
                        "script": {
                            "source": " (doc.medias.size() == 0 || doc.medias.view_count.size() == 0 ? 0 : doc.medias.view_count.value) "
                        }
                    
                    }
                }
            ],
            "query": {
                "match": {
                    "content": something"
                }
            },
            "score_mode": "multiply"
        }
    }
}

But I get this error:

"caused_by": {
                        "type": "illegal_argument_exception",
                        "reason": "No field found for [medias] in mapping with types []"
                    }

I guess I'm not accessing the view_count property correctly. How can I do that? And one more thing: the medias field is an array and if the size of the array exceeded 1 I need to get the maximum of the view_counts. How can I do this?

Val · Accepted Answer · 2020-09-09 08:43:14Z

1

Great start! You're almost there, you just need to access the doc values like this and you'll get the desired results :

    {
      "script_score": {
        "script": {
          "source": " (doc['medias.view_count'].size() == 0 ? 0 : doc['medias.view_count'].value) "
        }
      }
    }

Since doc['medias.view_count'] is actually a Java List, if you need to get the maximum of the view count you can do it like this:

    {
      "script_score": {
        "script": {
          "source": " (doc['medias.view_count'].size() == 0 ? 0 : doc['medias.view_count'].stream().max(Long::compare).get()) "
        }
      }
    }

edited Sep 9, 2020 at 8:43

answered Sep 9, 2020 at 8:21

Val

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3 Comments

Marzi Heidari Over a year ago

Thank you very much! just one more thing: the medias field is an array and if the size of the array exceeded 1 I need to get the maximum of the view_counts. How can I do this?

Marzi Heidari Over a year ago

And something else: When the medias has more than one element, your script view_count returns which one of them?

Val Over a year ago

doc['medias.view_count'] is actually a Java List, so you can get any positional element in that list. For instance, doc['medias.view_count'][2] would return the third view_count

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