README.md

hive-json-split

A simple UDF to split JSON arrays into Hive arrays.

Building

Check out the code and run

   mvn package

to build an uberjar with everything you need.

Split UDF

The split UDF accepts a single JSON string containing only an array. In the Hive CLI:

add jar target/JsonSplit-1.0-SNAPSHOT.jar;
create temporary function json_split as 'com.pythian.hive.udf.JsonSplitUDF';

create table json_example (json string);
load data local inpath 'split_example.json' into table json_example;

SELECT ex.* FROM json_example LATERAL VIEW explode(json_split(json_example.json)) ex;

json_split converts the string to the following array of structs, which are exploded into individual records:

[
  {
    row_id:1, 
    json_string:'1' 
  },
  { 
    row_id:2, 
    json_string:'2' 
  }, 
  {
    row_id:3, 
    json_string:'3' 
  }
]

You can access the JSON string for the element with the json_string attribute. The json_string can be any arbitrary JSON string, including another array or a nested object. row_id is the position in the array.

Map UDF

The map UDF accepts a flat JSON object (only integer and string values, no arrays or maps) and converts it into a Hive map. The elements of the map don't have to be defined until query-time, and can be accessed with the square bracket syntax ['key'].

add jar target/JsonSplit-1.0-SNAPSHOT.jar;
create temporary function json_map as 'com.pythian.hive.udf.JsonMapUDF';

create table json_map_example (json string);
load data local inpath 'map_example.json' into table json_map_example;

SELECT json_map(json)['x'] FROM json_map_example LATERAL VIEW explode(json_split(json_example.json)) ex;

The above converts the JSON string to a map, then pulls out the value for each record's key 'x'.