unsigned_long field type doesn't work with function_score decay functions

[mayya-sharipova]

Elasticsearch Version

8.4

Installed Plugins

No response

Java Version

bundled

OS Version

any

Problem Description

unsigned_long field type doesn't work with function_score decay functions, and produces an error:

"type" : "parsing_exception",
"reason" : "field [unsigned_long_test] is of type [org.elasticsearch.xpack.unsignedlong.UnsignedLongFieldMapper$UnsignedLongFieldType@10281e68], but only numeric types are supported."

Steps to Reproduce

1. Create index

PUT numeric-test-mapping
{
  "mappings": {
    "properties": {
      "double_test": {
        "type": "double"
      },
      "unsigned_long_test": {
        "type": "unsigned_long"
      },
      "long_test": {
        "type": "long"
      }
    }
  }
}

2. Create documents with numeric values for the 3 different fields

POST numeric-test-mapping/_doc/
{
  "double_test": 10, 
  "unsigned_long_test": 10,
  "long_test": 10
}
POST numeric-test-mapping/_doc/
{
  "double_test": 11, 
  "unsigned_long_test": 11,
  "long_test": 11
}

POST numeric-test-mapping/_doc/
{
  "double_test": 12, 
  "unsigned_long_test": 12,
  "long_test": 12
}

3. Run search on index created

GET numeric-test-mapping/_search 
{
  "from": 0,
  "size": 10,
  "query": {
    "function_score": {
    "functions": [
        {
            "gauss":{
                "unsigned_long_test":{
                  "scale": 1,
                  "origin": 0
                }
            }
        }]
    }
  }
}

Logs (if relevant)

No response

[elasticsearchmachine]

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