MongoDB code examples for Montreal.rb presentation # in Ruby

mongodb_at_montreal.rb

## Geolocation [ruby]
# First, create the index on a field containing long-lat values:
articles.create_index([["location", Mongo::GEO2D]])

# Then get a list of the twenty locations nearest to the point 50, 50:
articles.find({"location" => {"$near" => [50, 50]}}, {:limit => 20}).to_a

# collection.index_information() will get you a list of indexes on a Collection


## GridFS [ruby]
@db = Mongo::Connection.new.db('blog')
@grid = Grid.new(@db)

# Saving string data
id = @grid.put("here's some string / binary data")

# Saving IO data overriding attributes and including arbitrary metadata
file = File.open("me.jpg")
id2  = @grid.put(file, 
         :filename     => "my-avatar.jpg" 
         :content_type => "image/jpg", 
         :_id          => 'a-unique-id-to-use-in-lieu-of-a-random-one',
         :chunk_size   => 100 * 1024,
         :metadata     => {'description' => "taken during montreal.rb presentation"},
         :safe         => true) # MD5  checksum compared on client and server side

# Grid#put returns an object id, which you can use to retrieve the file:
# Get the string we saved
file = @grid.get(id)
image = @grid.get(id2)

# Get the file's metadata
image.filename # => "my-avatar.jpg"
image.content_type # => "image/jpg"
image.file_length # => 502357
image.upload_date # => Mon Feb 15 19:05:30 UTC 2011

## Capped collections [ruby]
@db = Mongo::Connection.new.db('log')
@db.create_collection("tail", :capped => true, :size => 100000, :max => 100)

## [ruby]
      # Assume map & reduce to be strings of javascript code
      @db = Mongo::Connection.new.db('blog')
      @db['articles'].map_reduce(map, reduce, :out => 'articles_tags_aggregation')

## Ruby driver overview [ruby]
gem install mongo
gem install bson_ext

# A Mongo::Connection instance represents a connection to MongoDB. 
# Use it to obtain an Mongo:DB instance, which represents a named database. 
# The database doesn't have to exist - if it doesn't, MongoDB will create it for you
db = Mongo::Connection.new("localhost", 27017).db("blog")

# Getting a collection
articles = db.collection("articles")

# Inserting a document
article = { 
  "title" => "MongoDB", 
  "tags" => ["database", "noSQL"], 
  "location" => {"long" => 203, "lat" => 102 } 
}
articles.insert(article)

# Querying for documents
articles.find(
  "created_at" => {"$lte" => Date.today, "$lte" => 3.days.ago}, 
  :fields => ["title", "created_at"]
).each { |article| puts article }

articles.find( "title" => /ruby$/i )

# Updating a document
articles.update({"_id" => article["_id"]}, {"$set" => {"title" => "MongoDB ♥ Ruby")

# Running  commands
command = {
  'findandmodify' => 'articles',
  'query' => { 'state' => 'draft' },
  'sort' => { 'created_at' => -1 },
  'update' => { '$set' => { 'state' => 'published' } }
}
db.command( command )



## Write concern
# The ruby driver implements a safe mode

# Wait for a response from the database
articles.save( { :title => 'foo' }, :safe => true ) 

# Wait until 2 servers have recorded the write
articles.save( { :title => 'foo' }, :safe => { :w => 2 } ) 

#  and time out if the replication can't be completed in 200 milliseconds
articles.save( { :title => 'foo' }, :safe => { :w => 2, :wtimeout => 200 } )

# and flush all pending writes to datafiles without waiting for the default interval (60 seconds)
articles.save( { :title => 'foo' }, :safe => { :w => 2, :wtimeout => 200, :fsync => true } ) 

# sets the safe mode for all writes from a connection
connection = Mongo::Connection.new( "localhost", 27017, :safe => {:w => 3} )