Elasticsearch: return only highlighted substring/keyword matches

Question

Given a full string Knasweg 12, 9062 Knasweg, Österreich, how do I highlight (and return) only the substring Knasweg if I search for this exact substring?

In other words, I'd like this query:

GET _search
{
  "query": {
    "match": {
      "location.pretty_address": {
        "query": "Knasweg",
        "operator": "and",
        "fuzziness": 1
      }
    }
  },
  "highlight": {
    "pre_tags": "",
    "post_tags": "",
    "fields": {
      "location.pretty_address": {
        "highlight_query": {
          "bool": {
            "must": {
              "match": {
                "location.pretty_address": {
                  "query": "Knasweg"
                }
              }
            }
          }
        }
      }
    }
  }
}

to return

  "highlight": {
    "location.pretty_address": [
      "Knasweg"
    ]
  }

instead of

  "highlight": {
    "location.pretty_address": [
      "Knasweg 12, 9062 Knasweg, Österreich"
    ]
  }    

---

My mapping:

"location": {
  "dynamic": "true",
  "properties": {
    "pretty_address": {
      "type": "text",
      "fields": {
        "keyword": {
          "type": "keyword"
        }
      },
      "analyzer": "autocomplete_analyzer"
    }
}

---

My settings:

"settings": {
  "index": {
    "analysis": {
      "analyzer": {
        "comma_analyzer": {
          "tokenizer": "comma_tokenizer"
        },
        "autocomplete_analyzer": {
          "filter": "lowercase",
          "tokenizer": "autocomplete_tokenizer"
        }
      },
      "tokenizer": {
        "autocomplete_tokenizer": {
          "type": "ngram",
          "min_gram": "3",
          "max_gram": "20"
        },
        "comma_tokenizer": {
          "pattern": ", ",
          "type": "pattern"
        }
      }
    }
  }
}

Answer 1

According to the documentation - here - you should add the fragment_size param and set it to 1 where 1 is the number of tokens in your query:

GET _search
{
  "query": {
    "match": {
      "location.pretty_address": {
        "query": "Knasweg",
        "operator": "and",
        "fuzziness": 1
      }
    }
  },
  "highlight": {
    "pre_tags": "",
    "post_tags": "",
    "fragment_size" : 1,
    "fields": {
      "location.pretty_address": {
        "highlight_query": {
          "bool": {
            "must": {
              "match": {
                "location.pretty_address": {
                  "query": "Knasweg"
                }
              }
            }
          }
        }
      }
    }
  }
}