How to make exact phrase matching in elastic search?

My guts tell me that your index has 5 primary shards and you don't have enough documents for the scores to be relevant. If you create an index with a single primary shard, your first query will return the document you expect. You can read more about the reason why this happens in the following article: https://www.elastic.co/blog/practical-bm25-part-1-how-shards-affect-relevance-scoring-in-elasticsearch

One way to achieve what you want is by using the keyword type but with a normalizer to lowercase the data so it's easier to search for exact matches in a case insensitive way.

Create your index like this:

PUT english{  "settings": {    "analysis": {      "normalizer": {        "lc_normalizer": {          "type": "custom",          "filter": ["lowercase"]        }      }    }  },  "mappings": {    "sentences": {      "properties": {        "sentence": {          "type": "text",          "fields": {            "exact": {              "type": "keyword",              "normalizer": "lc_normalizer"            }          }        }      }    }  }}

Then you can index your documents as usual.

PUT english/sentences/1{"sentence": "Today is a sunny day"}PUT english/sentences/2{"sentence": "Today is a sunny day but tomorrow it might rain"}...

Finally you can search for an exact phrase match, the query below will only return doc1

POST english/_search{  "query": {    "match": {      "sentence.exact": "today is a sunny day"    }  }}

Try using a bool query

    PUT test_index/doc/1    {"sentence": "Today is a sunny day"}    PUT test_index/doc/2    {"sentence": "Today is a sunny day but tomorrow it might rain"} -#terms query for exact match with keyword and multi match - phrase for other matches    GET test_index/_search    {      "query": {        "bool": {          "should": [            {              "terms": {                "sentence.keyword": [                  "Today is a sunny day"                ]              }            },            {                "multi_match":{                  "query":"Today is a sunny day",                "type":"phrase",                "fields":[                      "sentence"                ]              }            }          ]        }      }    }

Another option use multi match for both with keyword match as first and boost of 5 and other matches with no boost:

PUT test_index/doc/1{"sentence": "Today is a sunny day"}PUT test_index/doc/2{"sentence": "Today is a sunny day but tomorrow it might rain"}GET test_index/_search{    "query":{      "bool":{        "should":[          {            "multi_match":{              "query":"Today is a sunny day",            "type":"phrase",            "fields":[                "sentence.keyword"            ],            "boost":5          }        },        {            "multi_match":{              "query":"Today is a sunny day",            "type":"phrase",            "fields":[                  "sentence"            ]          }        }      ]    }  }}

This Query will work -

{    "query":{        "match_phrase":{            "sentence":{                "query":"Today is a sunny day"            }        }    },    "size":5,    "from":0,    "explain":false}