This extension is very interesting because it provides a procedural language created by the JavaScript V8 engine. It allows you to write functions in JavaScript and use them with SQL.

In the following example, you will create a function in JavaScript that makes a join between two JSON objects.

First, you will install the PLV8 extension and then the join_json function. This function accepts two JSON objects as parameters:

$ heroku pg:psql --app your-app-name
CREATE EXTENSION plv8;
CREATE OR REPLACE FUNCTION join_json(first JSON, second JSON)
RETURNS JSON AS $$
  for (var json_key in second) 
  { 
    first[json_key] = second[json_key]; 
  }
  return first;
$$ LANGUAGE plv8;

Finally, you will run SQL to make a union between the two JSON...