hadoop - 在 Hive 表中使用 JSON-SerDe

Question

我正在从下面的链接中尝试 JSON-SerDe http://code.google.com/p/hive-json-serde/wiki/GettingStarted .

         CREATE TABLE my_table (field1 string, field2 int, 
                                     field3 string, field4 double)
         ROW FORMAT SERDE 'org.apache.hadoop.hive.contrib.serde2.JsonSerde' ;

我添加了 Json-SerDe jar 作为

          ADD JAR /path-to/hive-json-serde.jar;

并将数据加载为

LOAD DATA LOCAL INPATH  '/home/hduser/pradi/Test.json' INTO TABLE my_table;

并成功加载数据。

但是当查询数据为

从我的表中选择*；

我只从表中得到一行

data1 100多个data1 123.001

Test.json 包含

{"field1":"data1","field2":100,"field3":"more data1","field4":123.001} 

{"field1":"data2","field2":200,"field3":"more data2","field4":123.002} 

{"field1":"data3","field2":300,"field3":"more data3","field4":123.003} 

{"field1":"data4","field2":400,"field3":"more data4","field4":123.004}

问题出在哪里？为什么当我查询表时只有一行而不是 4 行。在 /user/hive/warehouse/my_table 中包含所有 4 行!!

---

hive> add jar /home/hduser/pradeep/hive-json-serde-0.2.jar;
Added /home/hduser/pradeep/hive-json-serde-0.2.jar to class path
Added resource: /home/hduser/pradeep/hive-json-serde-0.2.jar

hive> CREATE EXTERNAL TABLE my_table (field1 string, field2 int,
>                                 field3 string, field4 double)
> ROW FORMAT SERDE 'org.apache.hadoop.hive.contrib.serde2.JsonSerde'
> WITH SERDEPROPERTIES (
>   "field1"="$.field1",
>   "field2"="$.field2",
>   "field3"="$.field3",
>   "field4"="$.field4"
> );
OK
Time taken: 0.088 seconds

hive> LOAD DATA LOCAL INPATH  '/home/hduser/pradi/test.json' INTO TABLE my_table;
Copying data from file:/home/hduser/pradi/test.json
Copying file: file:/home/hduser/pradi/test.json
Loading data to table default.my_table
OK
Time taken: 0.426 seconds

hive> select * from my_table;
OK
data1   100     more data1      123.001
Time taken: 0.17 seconds

我已经发布了 test.json 文件的内容。所以你可以看到查询结果只有一行

data1   100     more data1      123.001

---

我已将 json 文件更改为 employee.json，其中包含

{ “名字”:“迈克”， “姓氏”:“切佩斯基”， “员工编号”:1840192

还更改了表，但是当我查询表时它显示空值

hive> add jar /home/hduser/pradi/hive-json-serde-0.2.jar;
Added /home/hduser/pradi/hive-json-serde-0.2.jar to class path
Added resource: /home/hduser/pradi/hive-json-serde-0.2.jar

hive> create EXTERNAL table employees_json (firstName string, lastName string,        employeeNumber int )
> ROW FORMAT SERDE 'org.apache.hadoop.hive.contrib.serde2.JsonSerde';
OK
Time taken: 0.297 seconds


hive> load data local inpath '/home/hduser/pradi/employees.json' into table     employees_json;
Copying data from file:/home/hduser/pradi/employees.json
Copying file: file:/home/hduser/pradi/employees.json
Loading data to table default.employees_json
OK
Time taken: 0.293 seconds


 hive>select * from employees_json;
  OK
  NULL    NULL    NULL
  NULL    NULL    NULL
  NULL    NULL    NULL
  NULL    NULL    NULL
  NULL    NULL    NULL
  NULL    NULL    NULL
Time taken: 0.194 seconds

Answer 1

在有疑问的情况下，如果没有日志(请参阅 Getting Started)，很难说出发生了什么。只是一个快速的想法 - 如果它与 WITH SERDEPROPERTIES 一起工作，你能试试吗:

CREATE EXTERNAL TABLE my_table (field1 string, field2 int, 
                                field3 string, field4 double)
ROW FORMAT SERDE 'org.apache.hadoop.hive.contrib.serde2.JsonSerde'
WITH SERDEPROPERTIES (
  "field1"="$.field1",
  "field2"="$.field2",
  "field3"="$.field3",
  "field4"="$.field4" 
);

还有一个fork您可能想尝试一下 ThinkBigAnalytics。

更新:原来 Test.json 中的输入是无效的 JSON，因此记录被折叠。

查看答案 https://stackoverflow.com/a/11707993/396567了解更多详情。