Elasticsearch 5.2.2 : terms aggregation case insensitive

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，但我在使其工作时遇到了问题。

到目前为止，我尝试的是添加一个名为“lowercase”的自定义分析器，它使用“关键字”分词器和“lowercase”过滤器。然后，我为我要使用的字段添加了一个名为“use_lowercase”的映射字段。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 条作者相同但大小写不同的记录:

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"
}

到目前为止一切顺利。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文本而不是关键字，因此给我 fielddata 警告。我认为 ES 会足够复杂，可以识别 terms 字段实际上是一个关键字(通过自定义分析器)，因此可以进行聚合，但情况似乎并非如此。

如果我将 "fielddata":true 添加到 Author 的映射中，则聚合可以正常工作，但考虑到设置此值时堆使用率过高的可怕警告，我犹豫是否要这样做.

是否有执行此类不敏感关键字聚合的最佳做法？我希望我可以在 ma​​ppings 部分只说 "type":"keyword", "filter":"lowercase" 但这似乎不可用。

如果我走 "fielddata":true 路线，感觉就像我不得不使用太大的棍子才能让它工作。如有任何帮助，我们将不胜感激!

Answer 1

原来解决方案是使用自定义规范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
            }
          }
        }
      }
    }
  }
}

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