How to extract all the keys in a JSON object with BigQuery

Question

BigQuery has facilities to parse JSON in real-time interactive queries: Just store the JSON encoded object as a string, and query in real time, with functions like JSON_EXTR

Answer 1

This is what I came up with (Specifically for StandardSQL).. Not sure if accumulating in a list is the best method... Also.. I simplified for my case where I'm just concerned with keys.

CREATE TEMPORARY FUNCTION Foo(infoo STRING)
RETURNS Array
LANGUAGE js AS """
      blah = [];


      function processKey(node, parent) {
        if (parent !== '') {parent += '.'};
        Object.keys(node).forEach(function(key) {
          value = node[key].toString();
          if (value !== '[object Object]') {
            blah.push(parent+key) 
          } else {
            processKey(node[key], parent + key);
          };
        });                 
      };

    try {     
      x = JSON.parse(infoo);  
      processKey(x,'');
      return blah;
    } catch (e) { return null }      

"""
OPTIONS ();
WITH x as(
select Foo(jsonfield) as bbb from clickstream.clikcs
)
select distinct arr_item from (SELECT arr_item FROM x, UNNEST(bbb) as arr_item)