RICH-Informatik
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How to group and count results in Elasticsearch

Authors

How to group and count results in Elasticsearch

SQL query

SELECT Field, COUNT(Field)
FROM Table
GROUP BY Field

Query in Elasticsearch

GET /books/_search
{
  "size": 0,
  "aggs": {
    "genre": {
      "terms": {
        "field": "genre"
      }
    }
  }
}

Result

{
  "error": {
    "root cause" [
     {
      "type": "illegal _argument_exception",
      "reason" : "Text fields are not optimised for operations that require per-document field data like aggregations and sorting, so these operations are disabled by default. Please use a keyword field instead. Alternatively, set fielddata=true on [title] in order to load field data by uninverting the inverted index. Note that this can use significant memory."
     },
    ],
    ...
  }
}
PUT /books
{
  "mappings": {
    "properties": {
      "author":    { "type": "text" },
      "genre":  { "type": "keyword"  },
      "title":   { "type": "text"  }
    }
  }
}