Elasticsearch 5.2.2：术语聚合不区分大小写

Question

我正在尝试对关键字类型字段进行不区分大小写的聚合，但在使其工作时遇到问题。

到目前为止，我所尝试的是添加一个名为“小写”的自定义分析器，它使用“关键字”分词器和“小写”过滤器。然后，我将一个字段添加到我想要使用的字段的名为“use_lowercase”的映射中。我还想保留现有的“文本”和“关键字”字段组件，因为我可能想在该字段中搜索术语。

这是索引定义，包括自定义分析器：

PUT authors
{
  "settings": {
    "analysis": {
      "analyzer": {
        "lowercase": {
          "type": "custom",
          "tokenizer": "keyword",
          "filter": "lowercase"
        }
      }
    }
  },
  "mappings": {
    "famousbooks": {
      "properties": {
        "Author": {
          "type": "text",
          "fields": {
            "keyword": {
              "type": "keyword",
              "ignore_above": 256
            },
            "use_lowercase": {
              "type": "text",
              "analyzer": "lowercase"
            }
          }
        }
      }
    }
  }
}

现在我添加了 2 条具有相同作者的记录，但大小写不同：

POST authors/famousbooks/1
{
  "Book": "The Mysterious Affair at Styles",
  "Year": 1920,
  "Price": 5.92,
  "Genre": "Crime Novel",
  "Author": "Agatha Christie"
}

POST authors/famousbooks/2
{
  "Book": "And Then There Were None",
  "Year": 1939,
  "Price": 6.99,
  "Genre": "Mystery Novel",
  "Author": "Agatha christie"
}

到现在为止还挺好。现在，如果我根据作者进行术语聚合，

GET authors/famousbooks/_search
{
  "size": 0,
  "aggs": {
    "authors-aggs": {
      "terms": {
        "field": "Author.use_lowercase"
      }
    }
  }
}

我得到以下结果：

{
  "error": {
    "root_cause": [
      {
        "type": "illegal_argument_exception",
        "reason": "Fielddata is disabled on text fields by default. Set fielddata=true on [Author.use_lowercase] in order to load fielddata in memory by uninverting the inverted index. Note that this can however use significant memory."
      }
    ],
    "type": "search_phase_execution_exception",
    "reason": "all shards failed",
    "phase": "query",
    "grouped": true,
    "failed_shards": [
      {
        "shard": 0,
        "index": "authors",
        "node": "yxcoq_eKRL2r6JGDkshjxg",
        "reason": {
          "type": "illegal_argument_exception",
          "reason": "Fielddata is disabled on text fields by default. Set fielddata=true on [Author.use_lowercase] in order to load fielddata in memory by uninverting the inverted index. Note that this can however use significant memory."
        }
      }
    ],
    "caused_by": {
      "type": "illegal_argument_exception",
      "reason": "Fielddata is disabled on text fields by default. Set fielddata=true on [Author.use_lowercase] in order to load fielddata in memory by uninverting the inverted index. Note that this can however use significant memory."
    }
  },
  "status": 400
}

所以在我看来，聚合认为搜索字段是text而不是keyword，因此给了我 fielddata 警告。我认为 ES 足够复杂，可以识别出术语字段实际上是一个关键字（通过自定义分析器），因此可以聚合，但情况似乎并非如此。

如果我添加"fielddata":true到 Author 的映射中，那么聚合就可以正常工作，但是鉴于设置此值时堆使用率高的可怕警告，我很犹豫要不要这样做。

进行这种类型的不敏感关键字聚合是否有最佳实践？我希望我可以"type":"keyword", "filter":"lowercase"在映射部分说，但这似乎不可用。

如果我走这"fielddata":true条路，感觉就像我必须使用太大的棍子才能让它工作。对此的任何帮助将不胜感激！

Answer 1

事实证明，解决方案是使用自定义标准化器而不是自定义分析器。

PUT authors
{
  "settings": {
    "analysis": {
      "normalizer": {
        "myLowercase": {
          "type": "custom",
          "filter": [ "lowercase" ]
        }
      }
    }
  },
  "mappings": {
    "famousbooks": {
      "properties": {
        "Author": {
          "type": "text",
          "fields": {
            "keyword": {
              "type": "keyword",
              "ignore_above": 256
            },
            "use_lowercase": {
              "type": "keyword",
              "normalizer": "myLowercase",
              "ignore_above": 256
            }
          }
        }
      }
    }
  }
}

这样就可以Author.use_lowercase毫无问题地使用字段进行术语聚合。

Answer 2

好吧，您确实将 use_lowercase 定义为文本：

"use_lowercase": { "type": "text", "analyzer": "lowercase" }

尝试将其定义为type: keyword- 它帮助我解决了排序时遇到的类似问题。