r4vi / mongres

Mongo + Postgres (with plv8) = Mongres

Mongres is a PostgreSQL extension that runs a custom background worker speaks mongo wire protocol. The project is inspired by Mogoloid.

Install

• PostgreSQL 9.3
• PL/v8 1.3+
• mongo client

With postgres installed, make sure you have pg_config in your $PATH. Then, from the shell, run

make install

Create a database named mongres, and create extension plv8.

=# create database mongres
=# \c mongres
=# create extension plv8;

Edit postgresql.conf accordingly.

shared_preload_libraries = '$libdir/mongres,$libdir/plv8.so'

Finally, install functions.sql.

psql -f functions.sql mongres

Restart postgres, and type mongo. You should connect to mongres.

Screenshot

After starting the postgres, connect to mongres, insert 3 items into test.products.

$ mongo
MongoDB shell version: 2.0.1
connecting to: test
> db.products.insert( [ { _id: 11, item: "pencil", qty: 50, type: "no.2" },
...                       {          item: "pen", qty: 20 },
...                       {          item: "eraser", qty: 25 } ] )
Tue May 21 23:44:29 TypeError: res has no properties shell/db.js:546
> db.products.find()
{ "_id" : 11, "item" : "pencil", "qty" : 50, "type" : "no.2" }
{ "item" : "pen", "qty" : 20, "_id" : "ea746bc5b6cd48f2638880e0" }
{ "item" : "eraser", "qty" : 25, "_id" : "ccabfa394e2acb19a56f8645" }
> db.products.find({_id:11})
{ "_id" : 11, "item" : "pencil", "qty" : 50, "type" : "no.2" }
>

From psql, you should be able to see the data.

mongres=# table test.products;
            id            |                            data                             
--------------------------+-------------------------------------------------------------
 11                       | {"_id":11,"item":"pencil","qty":50,"type":"no.2"}
 ea746bc5b6cd48f2638880e0 | {"item":"pen","qty":20,"_id":"ea746bc5b6cd48f2638880e0"}
 ccabfa394e2acb19a56f8645 | {"item":"eraser","qty":25,"_id":"ccabfa394e2acb19a56f8645"}
(3 rows)

Limitation

This is currently a prototype. The following operations are supported.

• db.collection.find()
• db.collection.insert()

Any suggestions, and/or contributions are welcomed.