Keyword Analyzer¶

The keyword analyzer accepts a string or array of strings as a parameter and indexes them as single terms. Only exact matches on the field are returned.

Example¶

The following example index definition specifies an index on the summary field using the keyword analyzer:

{
  "mappings": {
    "fields": {
      "summary": {
        "type": "string",
        "analyzer": "lucene.keyword"
      }
    }
  }
}

Consider a collection named cases with the following documents:

{ "_id": 1, "summary": "No action required at this time." }
{ "_id": 2, "summary": "Case set aside for future action." }
{ "_id": 3, "summary": "Frank's case is ready for planning." }

The following query uses the index on the summary field:

db.cases.aggregate([
  {
     $search: {
       "text": {
         "query": "No action required at this time.",
         "path": "summary"
        }
     }
  }
])

The above query returns the following result:

{ "_id" : 1, "summary" : "No action required at this time." }

The following query returns no results:

db.cases.aggregate([
  {
     $search: {
       "text": {
         "query": "action",
         "path": "summary"
        }
     }
  }
])

Two documents in the collection contain the string action, but the keyword analyzer matches only documents in which the search term matches the entire contents of the field exactly.

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