Mappings with and without raw type of "multifield" type is behaving differently

Elastic Stack Elasticsearch
1

Hi,

I have the following mappings inorder to search and even for sorting that field.

           "description": {
              "type": "multi_field",
              "fields": {
                 "raw": {
                    "type": "string",
                    "index": "not_analyzed"
                 },
                 "description":
                 { 
                     "type": "string",
              "analyzer": "analyzer_startswith"

                 },
                 "sort_field":
                 {
                "type": "string",
                "analyzer": "keyword_analyzer"

                 }
              }
           }

}

And here are my analyzers:

"analysis": {
"analyzer": {
"keyword_analyzer": {
"filter": "lowercase",
"tokenizer": "keyword"
},
"analyzer_startswith": {
"filter": [
"lowercase"
],
"tokenizer": "whitespace"
},
"wordAnalyzer": {
"type": "custom",
"filter": [
"lowercase",
"asciifolding",
"nGram_filter"
],
"tokenizer": "whitespace"
},
"whitespace_analyzer": {
"type": "custom",
"filter": [
"lowercase",
"asciifolding"
],
"tokenizer": "whitespace"
}
},
"filter": {
"nGram_filter": {
"max_gram": "20",
"min_gram": "1",
"type": "nGram",
"token_chars": [
"letter",
"digit",
"punctuation",
"symbol"
]
}
}
}

These above settings am using...

And here is my query:

GET pdlfull/pdlfull_type/_search
{
"query": {
"match_phrase_prefix": {
"description": "a"
}
},
"sort": [
{
"description.sort_field": {
"order": "asc"
}
}
]
}

When am using the mappings that I kept above am getting one sort of results.
When I removed that raw field and executing the query am getting another sort of results.
May I know what is the reason and which is the best solution

Thanks.