How to score based on number of substring occurrences within a field in ElasticSearch

Question

I have an ElasticSearch document setup like so

{
  metadata: {
    content: \"\",
    other_fields: ...
  },
  other_fields: ...
}

and am query

Answer 1

I could not replicate your query -- too many typos/syntax issues. Here's what I could reconstruct:

Let's first create some sample docs

POST metaa/_doc
{
  "metadata": {
    "content": "test"
  }
}

POST metaa/_doc
{
  "metadata": {
    "content": "test test"
  }
}

POST metaa/_doc
{
  "metadata": {
    "content": "test test test"
  }
}

then querying & using script_score, inspired by this cool answer:

GET metaa/_search
{
  "query": {
    "function_score": {
      "query": {
        "multi_match": {
          "query": "test",
          "fields": [
            "metadata.content",
            "other_fields"
          ]
        }
      },
      "functions": [
        {
          "script_score": {
            "script": {
              "source": """
                def docval = doc['metadata.content.keyword'].value;
                String temp = docval.replace('test', "");
                return (docval.length() - temp.length()) / 4;
              """
            }
          },
          "filter": {
            "match": {
              "metadata.content": {
                "query": "test"
              }
            }
          },
          "weight": 3
        }
      ],
      "boost_mode": "replace",
      "score_mode": "sum"
    }
  }
}

yielding

[
  {
    "_index":"metaa",
    "_type":"_doc",
    "_id":"suh763EBG_KW3EFnjwNq",
    "_score":9.0,
    "_source":{
      "metadata":{
        "content":"test test test"
      }
    }
  },
  {
    "_index":"metaa",
    "_type":"_doc",
    "_id":"seh763EBG_KW3EFnewP6",
    "_score":6.0,
    "_source":{
      "metadata":{
        "content":"test test"
      }
    }
  },
  {
    "_index":"metaa",
    "_type":"_doc",
    "_id":"s-h_63EBG_KW3EFnMQMU",
    "_score":3.0,
    "_source":{
      "metadata":{
        "content":"test"
      }
    }
  }
]

_score = 9 -> 6 -> 3.

Note: you may want to perform some validity checks within the script (could be a simple try/catch). But that's an exercise for the reader.