Practices on Loading JSON Data to Hive

Last updated: 2020-02-28 20:02:31

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1. Connect to Hive

Log in to a master node of the EMR cluster, switch to the "hadoop" user, go to the Hive directory, and connect to Hive by running the following command:

[root@10 ~]# su hadoop
[hadoop@10 root]$ cd /usr/local/service/hive

2. Prepare data

Create a data file in JSON format. Compile the following code and save:

vim test.data
{"name":"Mary","age":12,"course":[{"name":"math","location":"b208"},{"name":"english","location":"b702"}],"grade":[99,98,95]}
{"name":"Bob","age":20,"course":[{"name":"music","location":"b108"},{"name":"history","location":"b711"}],"grade":[91,92,93]}

Store the data file in HDFS:

hadoop fs -put ./test.data /

3. Create a table

Connect to Hive:

[hadoop@10 hive]$ hive

Create a table based on the mapping:

hive> CREATE TABLE test ( name string, age int, course array<map<string,string>>, grade array<int>) ROW FORMAT SERDE 'org.apache.hive.hcatalog.data.JsonSerDe' STORED AS TEXTFILE;

4. Import data

hive>LOAD DATA INPATH '/test.data' into table test;

5. Check whether data import is successful

Query all data:

hive> select * from test;
OK
Mary    12    [{"name":"math","location":"b208"},{"name":"english","location":"b702"}]    [99,98,95]
Bob    20    [{"name":"music","location":"b108"},{"name":"history","location":"b711"}]   [91,92,93]
Time taken: 0.153 seconds, Fetched: 2 row(s)

Query the first score of each record:

hive> select grade[0] from test;
OK
99
91
Time taken: 0.374 seconds, Fetched: 2 row(s)

Query the name and location of the first course of each record:

hive> select course[0]['name'], course[0]['location'] from test;
OK
math    b208
music    b108
Time taken: 0.162 seconds, Fetched: 2 row(s)