copy_to

`copy_to`

copy_to 参数允许您将多个字段的值复制到一个组字段中，然后可以将其作为单个字段进行查询。

如果您经常搜索多个字段，您可以使用 copy_to 来搜索较少的字段，从而提高搜索速度。请参阅尽可能搜索较少的字段。

例如，可以将 first_name 和 last_name 字段复制到 full_name 字段，如下所示

resp = client.indices.create(
    index="my-index-000001",
    mappings={
        "properties": {
            "first_name": {
                "type": "text",
                "copy_to": "full_name"
            },
            "last_name": {
                "type": "text",
                "copy_to": "full_name"
            },
            "full_name": {
                "type": "text"
            }
        }
    },
)
print(resp)

resp1 = client.index(
    index="my-index-000001",
    id="1",
    document={
        "first_name": "John",
        "last_name": "Smith"
    },
)
print(resp1)

resp2 = client.search(
    index="my-index-000001",
    query={
        "match": {
            "full_name": {
                "query": "John Smith",
                "operator": "and"
            }
        }
    },
)
print(resp2)

response = client.indices.create(
  index: 'my-index-000001',
  body: {
    mappings: {
      properties: {
        first_name: {
          type: 'text',
          copy_to: 'full_name'
        },
        last_name: {
          type: 'text',
          copy_to: 'full_name'
        },
        full_name: {
          type: 'text'
        }
      }
    }
  }
)
puts response

response = client.index(
  index: 'my-index-000001',
  id: 1,
  body: {
    first_name: 'John',
    last_name: 'Smith'
  }
)
puts response

response = client.search(
  index: 'my-index-000001',
  body: {
    query: {
      match: {
        full_name: {
          query: 'John Smith',
          operator: 'and'
        }
      }
    }
  }
)
puts response

const response = await client.indices.create({
  index: "my-index-000001",
  mappings: {
    properties: {
      first_name: {
        type: "text",
        copy_to: "full_name",
      },
      last_name: {
        type: "text",
        copy_to: "full_name",
      },
      full_name: {
        type: "text",
      },
    },
  },
});
console.log(response);

const response1 = await client.index({
  index: "my-index-000001",
  id: 1,
  document: {
    first_name: "John",
    last_name: "Smith",
  },
});
console.log(response1);

const response2 = await client.search({
  index: "my-index-000001",
  query: {
    match: {
      full_name: {
        query: "John Smith",
        operator: "and",
      },
    },
  },
});
console.log(response2);

PUT my-index-000001
{
  "mappings": {
    "properties": {
      "first_name": {
        "type": "text",
        "copy_to": "full_name" 
      },
      "last_name": {
        "type": "text",
        "copy_to": "full_name" 
      },
      "full_name": {
        "type": "text"
      }
    }
  }
}

PUT my-index-000001/_doc/1
{
  "first_name": "John",
  "last_name": "Smith"
}

GET my-index-000001/_search
{
  "query": {
    "match": {
      "full_name": { 
        "query": "John Smith",
        "operator": "and"
      }
    }
  }
}

	`first_name` 和 `last_name` 字段的值将被复制到 `full_name` 字段。
	仍然可以分别查询 `first_name` 和 `last_name` 字段以获取名字和姓氏，但可以查询 `full_name` 字段以获取名字和姓氏。

一些重点：

复制的是字段值，而不是术语（术语是分析过程的结果）。
原始的 _source 字段不会被修改以显示复制的值。
可以将同一个值复制到多个字段，使用 "copy_to": [ "field_1", "field_2" ]

您不能使用中间字段递归复制。以下配置不会将数据从 field_1 复制到 field_3

resp = client.indices.create(
    index="bad_example_index",
    mappings={
        "properties": {
            "field_1": {
                "type": "text",
                "copy_to": "field_2"
            },
            "field_2": {
                "type": "text",
                "copy_to": "field_3"
            },
            "field_3": {
                "type": "text"
            }
        }
    },
)
print(resp)

const response = await client.indices.create({
  index: "bad_example_index",
  mappings: {
    properties: {
      field_1: {
        type: "text",
        copy_to: "field_2",
      },
      field_2: {
        type: "text",
        copy_to: "field_3",
      },
      field_3: {
        type: "text",
      },
    },
  },
});
console.log(response);

PUT bad_example_index
{
  "mappings": {
    "properties": {
      "field_1": {
        "type": "text",
        "copy_to": "field_2"
      },
      "field_2": {
        "type": "text",
        "copy_to": "field_3"
      },
      "field_3": {
        "type": "text"
      }
    }
  }
}

相反，从源字段复制到多个字段

resp = client.indices.create(
    index="good_example_index",
    mappings={
        "properties": {
            "field_1": {
                "type": "text",
                "copy_to": [
                    "field_2",
                    "field_3"
                ]
            },
            "field_2": {
                "type": "text"
            },
            "field_3": {
                "type": "text"
            }
        }
    },
)
print(resp)

const response = await client.indices.create({
  index: "good_example_index",
  mappings: {
    properties: {
      field_1: {
        type: "text",
        copy_to: ["field_2", "field_3"],
      },
      field_2: {
        type: "text",
      },
      field_3: {
        type: "text",
      },
    },
  },
});
console.log(response);

PUT good_example_index
{
  "mappings": {
    "properties": {
      "field_1": {
        "type": "text",
        "copy_to": ["field_2", "field_3"]
      },
      "field_2": {
        "type": "text"
      },
      "field_3": {
        "type": "text"
      }
    }
  }
}

copy_to 不支持值采用对象形式的字段类型，例如 date_range。

动态映射

编辑

将 copy_to 与动态映射一起使用时，请考虑以下几点：

如果目标字段在索引映射中不存在，则应用通常的动态映射行为。默认情况下，当 dynamic 设置为 true 时，一个不存在的目标字段将被动态添加到索引映射中。
如果 dynamic 设置为 false，则目标字段不会被添加到索引映射中，并且该值不会被复制。

如果 dynamic 设置为 strict，则复制到不存在的字段将导致错误。

如果目标字段是嵌套的，则 copy_to 字段必须指定嵌套字段的完整路径。省略完整路径将导致 strict_dynamic_mapping_exception。使用 "copy_to": ["parent_field.child_field"] 来正确定位嵌套字段。

例如：

resp = client.indices.create(
    index="test_index",
    mappings={
        "dynamic": "strict",
        "properties": {
            "description": {
                "properties": {
                    "notes": {
                        "type": "text",
                        "copy_to": [
                            "description.notes_raw"
                        ],
                        "analyzer": "standard",
                        "search_analyzer": "standard"
                    },
                    "notes_raw": {
                        "type": "keyword"
                    }
                }
            }
        }
    },
)
print(resp)

const response = await client.indices.create({
  index: "test_index",
  mappings: {
    dynamic: "strict",
    properties: {
      description: {
        properties: {
          notes: {
            type: "text",
            copy_to: ["description.notes_raw"],
            analyzer: "standard",
            search_analyzer: "standard",
          },
          notes_raw: {
            type: "keyword",
          },
        },
      },
    },
  },
});
console.log(response);

PUT /test_index
{
  "mappings": {
    "dynamic": "strict",
    "properties": {
      "description": {
        "properties": {
          "notes": {
            "type": "text",
            "copy_to": [ "description.notes_raw"], 
            "analyzer": "standard",
            "search_analyzer": "standard"
          },
          "notes_raw": {
            "type": "keyword"
          }
        }
      }
    }
  }
}

notes 字段被复制到 notes_raw 字段。仅定位 notes_raw 而不是 description.notes_raw 会导致 strict_dynamic_mapping_exception。

在此示例中，notes_raw 未在映射的根目录中定义，而是在 description 字段下定义。如果没有完全限定的路径，Elasticsearch 会将 copy_to 目标解释为根级别的字段，而不是 description 下的嵌套字段。

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