How to load a file with a JSON array per line in Pig Latin

问题

An existing script creates text files with an array of JSON objects per line, e.g.,

[{"foo":1,"bar":2},{"foo":3,"bar":4}]
[{"foo":5,"bar":6},{"foo":7,"bar":8},{"foo":9,"bar":0}]
…

I would like to load this data in Pig, exploding the arrays and processing each individual object.

I have looked at using the JsonLoader in Twitter’s Elephant Bird to no avail. It doesn’t complain about the JSON, but I get “Successfully read 0 records” when running the following:

register '/tmp/elephant-bird/core/target/elephant-bird-core-4.3-SNAPSHOT.jar';
register '/tmp/elephant-bird/hadoop-compat/target/elephant-bird-hadoop-compat-4.3-SNAPSHOT.jar';
register '/tmp/elephant-bird/pig/target/elephant-bird-pig-4.3-SNAPSHOT.jar';
register '/usr/local/lib/json-simple-1.1.1.jar';

a = load '/path/to/file.json' using com.twitter.elephantbird.pig.load.JsonLoader('-nestedLoad=true');
dump a;

I have also tried loading the file as normal, treating each line as a containing a single column chararray, and then trying to parse that as JSON, but I can’t find a pre-existing UDF which seems to do the trick.

Any ideas?

回答1:

Like Donald said, you should use a UDF here. Here in Xplenty we wrote JsonStringToBag to complement ElephantBird's JsonStringToMap.

来源：https://stackoverflow.com/questions/19863628/how-to-load-a-file-with-a-json-array-per-line-in-pig-latin