CODEWITHSUNDEEP
apache-pig
Neil
Neil

Reputation: 25815

How do you decode JSON in Pig that comes from a column?

There are numerous examples of how to use JsonLoader() to load JSON data with a schema from a file, but not from any sort of other output.

Upvotes: 1

Views: 942

Answers (1)

Garren S
Garren S

Reputation: 5782

You are looking for the JsonStringToMap UDF provided in Elephant Bird: https://github.com/kevinweil/elephant-bird/search?q=JsonStringToMap&ref=cmdform

Sample File:

foo     bar     {"version":1, "type":"an event", "count": 1}
foo     bar     {"version":1, "type":"another event", "count": 1}

Pig Script:

REGISTER /path/to/elephant-bird.jar;
DEFINE JsonStringToMap com.twitter.elephantbird.pig.piggybank.JsonStringToMap();
raw = LOAD '/tmp/file.tsv' USING PigStorage('\t') AS (col1:chararray,col2:chararray,json_string:chararray);
parsed = FOREACH raw GENERATE col1,col2,JsonStringToMap(json_string);
ILLUSTRATE parsed; -- Just to show the output

Pre-processing (JSON as chararray/string):

-------------------------------------------------------------------------------------------------------
| raw     | col1:chararray    | col2:chararray    | json_string:chararray                             | 
-------------------------------------------------------------------------------------------------------
|         | foo               | bar               | {"version":1, "type":"another event", "count": 1} |

Post-processing (JSON as map):

-------------------------------------------------------------------------------------------------
| parsed     | col1:chararray    | col2:chararray    | json:map(:chararray)                     | 
-------------------------------------------------------------------------------------------------
|            | foo               | bar               | {count=1, type=another event, version=1} | 
-------------------------------------------------------------------------------------------------

This question is a duplicate of How to parse a JSON string from a column with Pig

Upvotes: 2

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