有时候想看看es中某个索引中所有的字段，直接通过查询mapping是很难看出所有的字段的，里面包含的属性太多了。本博文将实现获取mapping中所有字段的算法。

示例new_user2索引中的mapping值：

{
	"new_user2": {
		"mappings": {
			"properties": {
				"address": {
					"properties": {
						"city": {
							"type": "text",
							"fields": {
								"keyword": {
									"type": "keyword",
									"ignore_above": 256
								}
							}
						},
						"province": {
							"type": "text",
							"fields": {
								"keyword": {
									"type": "keyword",
									"ignore_above": 256
								}
							}
						}
					}
				},
				"age": {
					"type": "long"
				},
				"name": {
					"type": "text",
					"fields": {
						"keyword": {
							"type": "keyword",
							"ignore_above": 256
						}
					}
				}
			}
		}
	}
}

示例代码：【直接在mapping中获取】

import json

with open('text.txt', 'r', encoding='utf-8') as f:
    data = f.read()

json_data = json.loads(data)
# print(json_data)

for key, value in json_data.items():
    index = key
    mappings = value


def func(dic):
    res = []

    def traceback(mapping, fields_join):
        if not isinstance(mapping, dict):
            return res.append(fields_join)
        for key, value in mapping.items():
            if fields_join:
                traceback(value, fields_join + '.' + key)
            else:
                traceback(value, key)

    def filter_fields(fields: list):
        fields_lst = []
        for field in fields:
            field = field.replace('mappings.properties.', '').replace('.properties', '')
            # 注意：下面几个判断最好替换字符串长的在前面，防止出错
            if field[-28:] == '.fields.keyword.ignore_above':
                field = field[:-28]
            elif field[-20:] == '.fields.keyword.type':
                field = field[:-20]
            elif field[-15:] == '.fields.keyword':
                field = field[:-15]
            elif field[-5:] == '.type':
                field = field[:-5]
            fields_lst.append(field)
        return list(set(fields_lst))

    traceback(dic, '')
    return filter_fields(res)


ret = func(mappings)
print("index: ", index)
print("fields: ", ret)

运行结果：

注意：也可以直接通过查询语句，直接在es中查询，通过响应的数据中获取：res['hits']['hits']。但是，由于查询出的数据未必所有字段都是有数据的，所有这种方法不是准确的。最好还是直接从获取到的_mapping中直接获取！