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Elasticsearch(027):es中Meta-Fields(元数据类型)之概述(_field_names)

程序员文章站 2022-04-23 22:09:56
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概述

该_field_names字段会索引文档中所有包含非空值的字段名称。_field_names字段用于存在查询和缺失查询的情况下,查询指定指定字段拥有非空值的文档是否存在。

注意:由于_field_names引入了一些索引时间开销,因此,如果要优化索引速度并且不需要exists查询,则可能需要禁用此字段。

使用示例

PUT example
PUT example/docs/_mapping
{
    "properties":{
        "id":{"type": "long"},
        "title":{"type": "text"},
        "content":{"type": "text"}
    }
}
PUT example/docs/1
{
    "id":1,
    "title": "This is a title"
}
PUT example/docs/2
{
    "id":2,
    "title": "This is another a title!!",
    "content": "content............"
}
PUT example/docs/3
{
    "id":3,
    "content": "content3333333333"
}

# 查询title非空的文档
GET example/docs/_search
{
    "query": {
        "exists": {
          "field": "title"
        }
    }
}

返回结果

{
  "took": 2,
  "timed_out": false,
  "_shards": {
    "total": 5,
    "successful": 5,
    "skipped": 0,
    "failed": 0
  },
  "hits": {
    "total": 2,
    "max_score": 1,
    "hits": [
      {
        "_index": "example",
        "_type": "docs",
        "_id": "2",
        "_score": 1,
        "_source": {
          "id": 2,
          "title": "This is another a title!!",
          "content": "content............"
        }
      },
      {
        "_index": "example",
        "_type": "docs",
        "_id": "1",
        "_score": 1,
        "_source": {
          "id": 1,
          "title": "This is a title"
        }
      }
    ]
  }
}

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