How to parse a JSON string from a column with Pig

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} | -------------------------------------------------------------------------------------------------

Here's the same question asked just two days ago: How do you decode JSON in Pig that comes from a column?

Check out Elephantbird (Twitter's library for all things Hadoop) - they have a UDF called JsonStringToMap which does exactly what you need (takes a string and transforms it into a map).