In the future we may support additional languages and if there's particular ones please feel free to drop us a line at postgres@heroku.com and let us know which ones you'd like and why.
SQL Server allows for .NET stored procedures, so you could already use something like JScript.NET.
I fail to see what you mean by thinking out of the box.
Third party handlers exist, off the top of my head, for JavaScript (obviously; see TFA), R, Ruby, Scheme and shell. That list probably isn't remotely exhaustive.
To be honest, though, I've never really had much of a use for any language other than pl/pgsql and occasionally pl/r; I try to keep anything too complicated outside of the database.
Postgres is awesome, but the JavaScript support from PL/V8 is a third-party extension, not a core database feature.
I don't think you'd say "well, Ruby is awesome but web application development support comes from a third-party project, not the standard library."
There are significant problems with stored procedures if they aren't used right. VARIADIC stored procedures help, but they don't entirely solve the problem. Fortunately PostgreSQL offers some rich tools for solving some of these problems. For example we make extensive use of named arguments.
But there is a second use here as well, and this is to extend what you can do inside a SQL query and when you combine this with JSON types, you can do quite a lot.
For example, suppose you do something like:
SELECT extract(myjsonfld, 'property1') FROM mytable WHERE id = 123;
There is no extract function in PostgreSQL 9.1-2 (there will be in 9.3 but not sure what the semantics will be), so you could write such a function in Javascript, such that it takes a JSON and string input and outputs a string or JSON object depending on what you want.
This allows you to extend the capabilities of SQL to do whatever you need.
During the afformentioned "Sproc Hell", we were putting application logic in the database. Of course, this made perfect sense: it was secure because of bound params and strict typing, it was fast because it avoided several trips to the database for multi query operations and even for single query statements, query plans were precomputed and cached by the DB. You were also able to tweak application logic without deploying code, which was likely a clumsy process involving more than one team and various manual steps. This is all bollocks, as we've learned many scars and gray hairs later.
Now, the proposal here is entirely different. While yes, you are creating a function in your database, you are doing it to access data in a JSON structure, per the OP. Because in Postgres you can create an index on the result of any expression, including a function, you can now create indexes on functions that parse and access data your JSON docs. And it's fast.
Now, what we do with LedgerSMB is build our stored procedures as basically named queries, inspired by web services (both SOAP and REST have been inspirations there). The procedures are intended to be relatively discoverable at runtime, with the aggressive attempts to use what infrastructure exists for this purpose that REST gives for HTTP.
Stored procedures are not a problem. They allow you to encapsulate a database behind an API, and the desire to do that is a major point of Martin Fowler's NoSQL advocacy (arguing for doing this for NoSQL dbs).
Because it doesn't have anything to do with "Stored Procedure hell". Having one more choice of procedural languages (of which there are already many available for Postgres) doesn't do anything to force you to adopt bad practices as to when you use procedural code in the database.
The example in this link and what a lot of us hope to use it for is schema-less data storage.
I'm not going to put any logic into my v8 functions except for accessing data.
This provides a safe and modular alternative to PL/PgSQL and PL/Perl, and lets us re-use client side models & validators in the database.
https://npmjs.org/package/pgrest builds on this work and offers a subset of MongoLab REST API for an existing Pg database, with the eventual aim of serving JSON APIs directly from the database, cutting out the middleware altogether.
We're also looking at adding Firebase-like ACLs into the mix.
Currently there's just the NPM doc'n and a bilingual presentation at https://speakerdeck.com/audreyt/pgrest-node-dot-js-in-the-da... —— documentation will appear on http://pgre.st/ as soon as the API solidifies.
Now I'm actually for polyglot programming and don't think you should do everything with just one tool (especially if its JavaScript), but for stored procedures you're not really losing a lot. This is scripting, after all. And the less said about the DB-"native" PLs, the better. I've still got nightmares about inappropriate use cases of PL/SQL (and hey, I actually like Ada).
Bonus fun: IBM DB2 has a PL/SQL front end that compiles to their own bytecode.
So you don't need different languages for client components, server components, and stored procs / db functions.
http://ledgersmbdev.blogspot.com/
They use PL/pgSQL to provide a bunch of service interfaces, then have Perl that provides automatic service discovery and object generation. Basically ORM from the inside out.
