json - 如何使用 Hive (get_json_object) 或 json serde 查询结构数组

Question

我正在尝试查询存储在我的 HDFS 上的以下 JSON 示例文件

{
    "tag1": "1.0",
    "tag2": "blah",
    "tag3": "blahblah",
    "tag4": {
        "tag4_1": [{
                "tag4_1_1": [{
                        "tag4_1_1_1": {
                            "Addr": {
                                "Addr1": "blah",
                                "City": "City",
                                "StateProvCd": "NY",
                                "PostalCode": "99999"
                            }
                        }
                        "tag4_1_1_1": {
                            "Addr": {
                                "Addr1": "blah2",
                                "City": "City2",
                                "StateProvCd": "NY",
                                "PostalCode": "99999"
                            }
                        }
                    }
                ]
            }
        ]
    }
}

我使用以下内容在数据上创建外部表

CREATE  EXTERNAL TABLE DB.hv_table
(
  tag1 string
, tag2 string
, tag3 string
, tag4 struct<tag4_1:ARRAY<struct<tag4_1_1:ARRAY<struct<tag4_1_1_1:struct<Addr
                Addr1:string
                , City:string
                , StateProvCd:string
                , PostalCode:string>>>>>>
)
ROW FORMAT SERDE 'org.apache.hive.hcatalog.data.JsonSerDe' 
LOCATION 'HDFS/location';

理想情况下，我想查询数据，使其返回给我:

select tag1, tag2, tag3, tag4(all data) from DB.hv_table;

有人可以为我提供一个示例，说明如何在不以以下方式编写的情况下进行查询:

select tag1, tag2, tag3
, tag4.tag4_1[0].tag4_1_1[0].tag4_1_1_1.Addr.Addr1 as Addr1 
, tag4.tag4_1[0].tag4_1_1[0].tag4_1_1_1.Addr.City as City 
, tag4.tag4_1[0].tag4_1_1[0].tag4_1_1_1.Addr.StateProvCd as StateProvCd 
, tag4.tag4_1[0].tag4_1_1[0].tag4_1_1_1.Addr.PostalCode as PostalCode 
from DB.hv_table

最重要的是，我不想定义数组项元素编号。在我的示例中，我只能定位数组的第一个元素 (tag4_1_1_1)。如果可能的话，我会瞄准一切。

Answer 1

在以下位置找到了一个非常好的博客:ThornyDev

CREATE EXTERNAL TABLE IF NOT EXISTS DB.dummyTable (jsonBlob STRING)
LOCATION 'pathOfYourFiles';

SELECT 
get_json_object(jsonBlob, '$.tag1') AS tag1
,get_json_object(jsonBlob, '$.tag2') AS tag2
,get_json_object(jsonBlob, '$.tag3') AS tag3
,get_json_object(jsonBlob, '$.tag4.tag4_1.tag4_1_1.tag4_1_1_1.Addr.Addr1') AS Addr1
,get_json_object(jsonBlob, '$.tag4.tag4_1.tag4_1_1.tag4_1_1_1.Addr.City') AS City
,get_json_object(jsonBlob, '$.tag4.tag4_1.tag4_1_1.tag4_1_1_1.Addr.StateProvCd') AS StateProvCd
,get_json_object(jsonBlob, '$.tag4.tag4_1.tag4_1_1.tag4_1_1_1.Addr.PostalCode') AS PostalCode
FROM DB.dummyTable

我很满意，但我想查看 json 元组，看看它与“get_json_object”类的性能如何