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()
andfindAndModify()
(v2.6+) - Write concern support (v2.6+)
- Optimised queries for
findOne()
andfindAll()
- Cursor support
- Aggregation commands:
aggregate()
,distinct()
,group()
andmapReduce()
- Index support:
create()
,ensure()
anddrop()
- User support:
create()
,drop()
,grant()
andrevoke()
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.
ALIEN-AID: See Morphia for a complete Fantom to MongoDB object mapping library!
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.
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
v0.0.6
- Bug:
Index.ensure()
when comparing indexes did not respectunique:false
.
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