Multiply parent doc _score and the _score from function_score with nested query

Question

What I want is to get all documents which match query terms in Title field, and boost the score by value of a field in nested object if the query term also exactly match that nested field.

Following is my example doc:

{
  "Title": "The Heart of the Elastic Stack"
  "QueryClicks": [
      { "Term": "elastic stack", "Count": 100},
      { "Term": "elastic", "Count": 50},
      { "Term": "hard of the elastic", "Count": 200},
  ]
}

And example query DSL:

{
  "query" : {
    "bool" : {
      "must" : [{
          "match" : {
            "Title" : "elastic stack"
          }
        }
      ],
      "should" : [{
          "nested" : {
            "path" : "QueryClicks",
            "query" : {
              "function_score" : {
                "query" : {
                  "match" : {
                    "QueryClicks.Term.lowercaseraw" : "elastic stack"
                  }
                },
                "functions" : [{
                    "script_score" : {
                      "script" : "log(doc['QueryClicks.Count'].value*4)"
                    }
                  }
                ],
                "boost_mode" : "replace"
              }
            }
          }
        }
      ]
    }
  }
}

It somehow works, for certain queryterm, if it match one of the QueryClicks.Term, extra scores will be added to the whole score of the document.

But not perfect, what I want is to multiply the nested function score (that is, log(doc['QueryClicks.Count'].value*4) ) with the parent document's score which calculated in must clause.

If I can get the parent doc's score, then I can do something like this:

"script": "log(doc['QueryClicks.Count'].value*4) * _parent_score"

But since ES does not support getting parent score from nested query yet. Any other approaches?

The purpose is, multiply the _score which calculated by QueryClicks.Count and the _score from must query clause.

in order to multiply function score with query score boost_mode should be multiply. — user3775217

user3775217 user3775217 · Accepted Answer · 2016-12-29T09:24:14

You have used boost_mode as replace. This will neglect your score generated by query. Your current settings for function score will replace score of document with that score of function query only.

To multiply both the score of function query and score generated by query use the following query

{
    "query": {
        "bool": {
            "must": [{
                "match": {
                    "Title": "elastic stack"
                }
            }],
            "should": [{
                "nested": {
                    "path": "QueryClicks",
                    "query": {
                        "function_score": {
                            "query": {
                                "match": {
                                    "QueryClicks.Term.lowercaseraw": "elastic stack"
                                }
                            },
                            "functions": [{
                                "script_score": {
                                    "script": "log(doc['QueryClicks.Count'].value*4)"
                                }
                            }],
                            "boost_mode": "multiply",
                            "score_mode": "sum"
                        }
                    }
                }
            }]
        }
    }
}

Here you can replace score_mode accordingly how you want to evaluate the function score for each score inside the function.

Hope this works for you. Thanks

Multiply parent doc _score and the _score from function_score with nested query

2 Answers