Elasticsearch 5.2.2 : terms aggregation case insensitive

我正在尝试对关键字类型字段进行不区分大小写的聚合，但是在使它起作用时遇到了问题。

到目前为止，我已经尝试添加一个名为“lowercase”的自定义分析器，该分析器使用“keyword” token 生成器和“lowercase”过滤器。然后，我为要使用的字段在映射中添加了一个名为“use_lowercase”的字段。我也想保留现有的“文本”和“关键字”字段组件，因为我可能想在字段中搜索术语。

这是索引定义，包括定制分析器:

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Author(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"
}

到现在为止还挺好。现在，如果我根据作者进行条款汇总，

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
}

因此，在我看来，聚合正在考虑搜索字段是文本而不是关键字，因此给了我字段数据警告。我认为ES足够复杂，可以识别条件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，但是事实并非如此。

如果我将"fielddata":true添加到Author的映射中，则聚合可以正常工作，但是鉴于设置此值时会出现堆使用率过高的可怕警告，因此我很犹豫。

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

如果我走"fielddata":true路线，那感觉就像我不得不使用太大的棍子才能使它正常工作。任何帮助，将不胜感激!

最佳答案

事实证明，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
            }
          }
        }
      }
    }
  }
}

然后，这将允许使用字段Author.use_lowercase进行术语聚合而不会出现问题。

关于Elasticsearch 5.2.2 : terms aggregation case insensitive，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/42517001/