MongoUser Guide

Overview

Mongo is a pure Fantom driver for MongoDB v2.6+.

Mongo driver features:

  • Standard and capped collections
  • Write commands: insert(), update(), delete() and findAndModify() (v2.6+)
  • Write concern support (v2.6+)
  • Optimised queries for findOne() and findAll()
  • Cursor support
  • Aggregation commands: aggregate(), distinct(), group() and mapReduce()
  • Index support: create(), ensure() and drop()
  • User support: create(), drop(), grant() and revoke() roles
  • Database authentication
  • Server side eval() commands
  • Pooled connection manager for multi-threaded use

Mongo driver has been written specifically for MongoDB v2.6.0 released on 8th April 2014, or newer.

Many features, including ALL write commands, will NOT work with older MongoDB versions.

Install

Install Mongo with the Fantom Repository Manager ( fanr ):

C:\> fanr install -r http://repo.status302.com/fanr/ afMongo

To use in a Fantom project, add a dependency to build.fan:

depends = ["sys 1.0", ..., "afMongo 0.0+"]

Documentation

Full API & fandocs are available on the Status302 repository.

Quick Start

1). Start up an instance of MongoDB:

C:\> mongod

MongoDB starting
db version v2.6.0
waiting for connections on port 27017

2). Create a text file called Example.fan:

using afBson
using afMongo
using concurrent

class Example {

    Void main() {
        mongoClient := MongoClient(ActorPool(), `mongodb://localhost:27017`)
        collection  := mongoClient.db("friends").collection("birds")

        documentIn  := [
            "_id"   : ObjectId(),
            "name"  : "Emma",
            "score" : 9
        ]
        collection.insert(documentIn)

        echo( collection.findAll.first )

        mongoClient.shutdown
    }
}

3). Run Example.fan as a Fantom script from the command line:

C:\> fan Example.fan

     Alien-Factory
 _____ ___ ___ ___ ___
|     | . |   | . | . |
|_|_|_|___|_|_|_  |___|
              |___|0.0.4

Connected to MongoDB v2.6.0 (at mongodb://localhost:27017)

[_id:5373acbda8000b3491000001, name:Emma, score:9]

Usage

MongoClient is the main entry point into Mongo. From there you can access all other components of MongoDB, namely Database, Collection, Index and User.

MongoClient
 `-- Database
      +-- Collection
      |    `-- Index
      `-- User

Connecting

MongoClient is created with a ConnectionManager, which manages your connections to MongoDB. Use ConnectionManagerPooled for normal multi-threaded use:

conMgr := ConnectionManagerPooled(ActorPool(), `mongodb://localhost:27017`)
client := MongoClient(conMgr)

When you create a MongoClient it immediately connects to MongoDB and verifies it is the correct version:

.    Alien-Factory
 _____ ___ ___ ___ ___
|     | . |   | . | . |
|_|_|_|___|_|_|_  |___|
              |___|0.0.4

Connected to MongoDB v2.4.9

[warn] ****************************************************************************
[warn] ** WARNING: This driver is ONLY compatible with MongoDB v2.6.0 or greater **
[warn] ****************************************************************************

Ooops! As you can see, we have an old MongoDB running. And true enough, when we run the QuickStart example we get:

afMongo::MongoCmdErr: Command 'insert' failed. MongoDB says: no such cmd: insert

Installing a fresh MongoDB of version 2.6.0 or greater will get you back on track.

Queries

Mongo and MongoDB work with documents, they are used throughout the Mongo API. A MongoDB document is represented in Fantom as a Map of type [Str:Obj?]. All document keys must be strings. Document values can be any valid BSON type.

ALIEN-AID: See the upcoming Alien-Factory Morphia library for complete Fantom to MongoDB object mapping!

A MongoDB database stores documents in collections. Use the find() methods to query a collection. Using the friends database in the QuickStart Example we could do:

collection.findOne( ["name":"Emma"] )       // --> return the doc where 'name == Emma'
                                            //     ('Emma' must be unique)

collection.findAll                          // --> return ALL docs in the collection
collection.findAll( ["name":"Emma"] )       // --> return all docs where 'name == Emma'
collection.findAll( ["score": ["\$gt":7]] ) // --> return all docs with 'score > 7'

The $gt expression is an example of a Query operator.

To iterate over a massive collection without loading it all into memory, use a Cursor. Cursors download documents in batches, behind the scenes, as and when required. Create and use a Cursors by using the find() method:

collection.find( ["score": ["\$gt":2]] ) |cursor| {
    cursor.batchSize = 10

    while (cursor.hasNext)
        doc := cursor.next
        ...
    }
}

Write Commands

The insert() command is simple enough and is demonstrated in the QuickStart example.

update() and delete() are similar in that they both take a query that describes which document(s) are to be updated / deleted. For most usages this will a simply be the id of the document in question:

collection.update( ["_id": objId], [ ...new doc...] )

Note that as of MongoDB v2.6 there is longer any need to call a getLastError() function. All error handling is done via write concerns. By default Mongo will throw a MongoErr should a write error occur.

ObjectId

All documents held in a collection need a unique id, held in a field named _id. If the _id field does not exist, MongoDB will create one for you of type ObjectId.

Note that _id does not need to an ObjectId, it can be any BSON type. It just needs to be unique in the collection.

Like marmite, people tend to have a love / hate relationship with the ObjectId. The good comments revolve around it having a natural sort that (roughly) corresponds to creation time. The bad is that in humongous collections it eats up precious bytes which means the index can't fit into RAM.

Remarks

The Alien-Factoy MongoDB driver was inspired by fantomongo by Liam Staskawicz.

Release Notes

v0.0.4

  • New: ConnectionManagerPooled instances are created with a Mongo Connection URI.
  • New: ConnectionManagerPooled accepts default database and user credentails to initially authenticate all leased connections with.

v0.0.2

  • New: Preview Release