使用HIVE解析json数组

Question

我有很多json数组存储在一个表(jt)中,如下所示:

[{"ts":1403781896,"id":14,"log":"show"},{"ts":1403781896,"id":14,"log":"start"}]
[{"ts":1403781911,"id":14,"log":"press"},{"ts":1403781911,"id":14,"log":"press"}]

每个阵列都是一个记录.

我想解析这个表,以获得一个包含3个字段的新表(日志):ts,id,log.我尝试使用get_json_object方法,但似乎该方法与json数组不兼容,因为我只获取空值.

这是我测试过的代码:

CREATE TABLE logs AS 
SELECT get_json_object(jt.value, '$.ts') AS ts, 
get_json_object(jt.value, '$.id') AS id,
get_json_object(jt.value, '$.log') AS log
FROM jt;

我试图使用其他功能,但它们看起来很复杂.谢谢!:)

更新!我通过执行regexp解决了我的问题:

CREATE TABLE jt_reg AS
select regexp_replace(regexp_replace(value,'\\}\\,\\{','\\}\\\n\\{'),'\\[|\\]','') as valuereg  from jt;


CREATE TABLE logs AS 
SELECT get_json_object(jt_reg.valuereg, '$.ts') AS ts, 
get_json_object(jt_reg.valuereg, '$.id') AS id,
get_json_object(jt_reg.valuereg, '$.log') AS log
FROM ams_json_reg;

Answer 1

使用 explode()函数

 hive (default)> CREATE TABLE logs AS
                  >   SELECT get_json_object(single_json_table.single_json, '$.ts') AS ts,
                  >   get_json_object(single_json_table.single_json, '$.id') AS id,
                  >   get_json_object(single_json_table.single_json, '$.log') AS log
                  >   FROM
                  >     (SELECT explode(json_array_col) as single_json FROM jt) single_json_table ;

Automatically selecting local only mode for query
Total MapReduce jobs = 3
Launching Job 1 out of 3
Number of reduce tasks is set to 0 since there's no reduce operator

hive (default)> select * from logs;
OK
ts      id      log
1403781896      14      show
1403781896      14      start
1403781911      14      press
1403781911      14      press
Time taken: 0.118 seconds, Fetched: 4 row(s)
hive (default)>

其中json_array_col是jt中保存jsons数组的列.

hive (default)> select json_array_col from jt;
json_array_col
["{"ts":1403781896,"id":14,"log":"show"}","{"ts":1403781896,"id":14,"log":"start"}"]
["{"ts":1403781911,"id":14,"log":"press"}","{"ts":1403781911,"id":14,"log":"press"}"]

Answer 2

我刚刚遇到了这个问题，JSON 数组作为字符串存储在 hive 表中。

该解决方案有点笨拙和丑陋，但它有效并且不需要 serdes 或外部 UDF

SELECT 
       get_json_object(single_json_table.single_json, '$.ts') AS ts,
       get_json_object(single_json_table.single_json, '$.id') AS id,
       get_json_object(single_json_table.single_json, '$.log') AS log
FROM ( SELECT explode (
  split(regexp_replace(substr(json_array_col, 2, length(json_array_col)-2),
            '"}","', '"}",,,,"'), ',,,,')
      ) FROM src_table) single_json_table;

我把行拆开，这样会更容易阅读。我正在使用 substr() 去除第一个和最后一个字符，删除 [ 和 ] 。然后我使用 regex_replace 来匹配 json 数组中记录之间的分隔符，并将分隔符添加或更改为独特的东西，然后可以轻松地与 split() 一起使用将字符串转换为 json 对象的 hive 数组，然后如上一个解决方案中所述，与explode() 一起使用。

请注意，此处使用的分隔符正则表达式 ( "}"," ) 不适用于原始数据集...正则表达式必须为 ( "},\{" )，然后替换为 "} ,,,,{" 例如..

  split(regexp_replace(substr(json_array_col, 2, length(json_array_col)-2),
            '"},\\{"', '"},,,,{"'), ',,,,')