plv8-javascript-modules-loading.sql

/******************************************************************************
How to load Javascript modules into postgres
******************************************************************************/
CREATE EXTENSION IF NOT EXISTS plv8

/******************************************************************************
First step is download the Javascript module file 
Example with undescore-min and node-jpath
******************************************************************************/

wget http://underscorejs.org/underscore-min.js
wget https://raw.github.com/adunstan/plv8-jpath/master/lib/plv8-jpath.js

/******************************************************************************
Open postgres console and set runtime variable to 
use the code later
******************************************************************************/

psql -d <database>
\set underscore `cat underscore-min.js`
\set jpath `cat plv8-jpath.js`

/******************************************************************************
Now that we have set variable containing the code
we need to create a table to store each of them in
postgres. 
******************************************************************************/

create table plv8_modules(modname text primary key, load_on_start boolean, code text);

insert into plv8_modules values ('underscore',true,:'underscore'),
    ('jpath',true,:'jpath');

/******************************************************************************
Create a a startup function to create a plv8 function
that will be used to load the modules, Executing it 
will register the plv8 function
******************************************************************************/

create or replace function plv8_startup()
returns void
language plv8
as
$$
load_module = function(modname) {
  var rows = plv8.execute("SELECT code from plv8_modules " +" where modname = $1", [modname]);
  for (var r = 0; r < rows.length; r++) {
    var code = rows[r].code;
    eval("(function() { " + code + "})")();
  }      
};
$$;

select plv8_startup();

/******************************************************************************
Load both modules into postgres using the previously created plv8 function
******************************************************************************/

do language plv8 ' load_module("underscore"); load_module("jpath"); ';

/******************************************************************************
Test the underscore module's extend function
******************************************************************************/

do language plv8 $$ 
  x = { 'a':1 }; 
  y=_.extend(x, { 'a':2,'b':3 }, { 'b':4, 'c':5 }); 
  plv8.elog(NOTICE,JSON.stringify(y)); 
$$;

/******************************************************************************
Test jpath module's filter function (github module example)
******************************************************************************/

do language plv8 $$
  var jsonData = {
    people: [
      { name: "John", age: 26, gender: "male" },
      { name: "Steve", age: 24, gender: "male" },
      { name: "Susan", age: 22, gender: "female" },
      { name: "Linda", age: 30, gender: "female" },
      { name: "Adam", age: 32, gender: "male"}
    ]
  };
  //Get all males younger then 25
  var match = jpath.filter(jsonData, "people[gender=male && age < 25]");
  plv8.elog(NOTICE,JSON.stringify(match));
$$;