Elastic Search error - variable [relevancy] is not defined - elasticsearch

Question

I am trying to query my products ElasticSearch index and create a script_score but I keep receiving the error Variable [relevancy] is not defined.
I tried replacing the script with just a number, then with Math.log(_score) to make sure the script_score was working properly and the math function is ok, and both queries executed as expected. I also tried doc['relevancy'].value and received the same error.
My query is:
curl -X GET "localhost:9200/products/_search?pretty" -H 'Content-Type: application/json' -d'
{
"query": {
"function_score": {
"query": {
"multi_match" : {
"query": "KQ",
"fields": [ "item_id", "extended_desc", "mfg_part_no" ]
}
},
"script_score" : {
"script": "Math.log(_score) + Math.log(doc['relevancy'])"
},
"boost_mode": "replace"
}
}
}
'
And the mapping for this index is:
{
"products" : {
"mappings" : {
"properties" : {
"#timestamp" : {
"type" : "date"
},
"#version" : {
"type" : "text",
"fields" : {
"keyword" : {
"type" : "keyword",
"ignore_above" : 256
}
}
},
"extended_desc" : {
"type" : "text",
"fields" : {
"keyword" : {
"type" : "keyword",
"ignore_above" : 256
}
}
},
"frecno" : {
"type" : "long"
},
"item_id" : {
"type" : "text",
"analyzer" : "my_analyzer"
},
"mfg_part_no" : {
"type" : "text",
"fields" : {
"keyword" : {
"type" : "keyword",
"ignore_above" : 256
}
}
},
"relevancy" : {
"type" : "long"
}
}
}
}
}

Answer 1

Replaced ' with \u0027 because this is curl.
curl -X GET "localhost:9200/products/_search?pretty" -H 'Content-Type: application/json' -d'
{
"query": {
"function_score": {
"query": {
"multi_match" : {
"query": "KQ",
"fields": [ "item_id", "extended_desc", "mfg_part_no" ]
}
},
"script_score" : {
"script": "Math.log(_score) + Math.log(doc[\u0027relevancy\u0027].value)"
},
"boost_mode": "replace"
}
}
}
'