Match phrase prefix not resulting based on exact match

Elastic Stack Elasticsearch
1

Hi,

I am using match phrase prefix for auto suggestion for _all
Eg: I do have entries in my type such as "PIPE","TUBE PIPE"
and when I am doing search using "PIPE" both are resulting but "TUBE PIPE" is getting highest score and resulting on top
I am expecting PIPE to come first

Below are the settings for my index

"settings" : {
"index" : {
"analysis" : {
"filter" : {
"nGram_filter" : {
"token_chars" : [ "letter", "digit", "punctuation" ],
"min_gram" : "1",
"type" : "nGram",
"max_gram" : "20"
}
},
"analyzer" : {
"desc_analyzer" : {
"type" : "custom",
"filter" : [ "lowercase", "asciifolding", "nGram_filter" ],
"tokenizer" : "keyword"
},
"nGram_analyzer" : {
"filter" : [ "lowercase", "asciifolding", "nGram_filter" ],
"type" : "custom",
"tokenizer" : "whitespace"
}
}
}

query:

"query": {
"match_phrase_prefix": {
"_all": {
"query": "PIPE",
"analyzer" : "standard"
}
}
}

Could you please suggest on this.

Thanks,
Rajesh