Mongodb and Mongomapper

MongoDB MongoMapper Ruby Replica Set Config

I ended up doing this:

MongoMapper.connection = Mongo::MongoReplicaSetClient.new(
['10.5.5.5:27017', '10.5.5.6:27017'],
:read => :primary, :rs_name => 'name', :connect_timeout => 30, :op_timeout => 30
)
MongoMapper.database = "db_name"
MongoMapper.database.authenticate("user", "test123")

Works beautifully.

rails 4 with mongoid or mongomapper ? which is perfect for own product

Mongoid has been officially incorporated under the MongoDB umbrella. It is a more mature product and it's actively developed, compared with MongoMapper.

I'd definitely not use MongoMapper for a new project.

What is the difference between mongodb and mongomapper?

MongoMapper is just a Ruby API for connecting to, querying, and updating a MongoDB databse.

How to do build this mongoDB query (mongomapper)

Thanks to @Simon I had a look at Map Reduce with MongoMapper. My take on it is probably not perfect, but it does what I want it to do. Here's the implementation:

class ChildTemplate
  ...
  key :name, String
  key :version, Integer, :default => 1

  ...

  private
  def self.map
    <<-JS
    function() {
      emit(this.name, this);
    }
    JS
  end

  private
  def self.reduce
    <<-JS
    function(key, values) {
      var res = values[0];
      for(var i=1; i<values.length; i++)
      {
        if(values[i].version > res.version)
        {
          res = values[i];
        }
      }
      return res;
    }           
end

def self.latest_versions(opts = {})
  results = []
  opts[:out] = "ct_latest_versions"
  ChildTemplate.collection.map_reduce(map, reduce, opts).find().each do |map_hash|
    results << map_hash["value"]
  end
  return results
end

Find documents including element in Array field with mongomapper?

In the current versions of MongoMapper, this will work:

MessageThread.where(:partecipant_ids => 15)

And this should work as well...

MessageThread.where(:partecipant_ids => [15])

...because plucky autoexpands that to:

MessageThread.where(:partecipant_ids => { :$in => [15] })

(see https://github.com/jnunemaker/plucky/blob/master/lib/plucky/criteria_hash.rb#L121)

I'd say take a look at your data and try out queries in the Mongo console to make sure you have a working query. MongoDB queries translate directly to MM queries except for the above (and a few other minor) caveats. See http://www.mongodb.org/display/DOCS/Querying

Advice on migrating from MongoMapper to Mongoid?

Both of them are great MongoDB Libraries for Ruby. But if you want to switch, here are some notes:

Migrating MongoMapper ORM to Mongoid ORM - Notes

• Configure the database connection.

• Replace configuration yaml file(includes replica configuration).

• Configure Mongoid specific options. e.g - raise_not_found_error: false. if you don't want an error every time a query returns nothing...

• Change all models definations - include MongoMapper::Document to include Mongoid::Document

• Change the format for all fields definitions.

• In mongoid, you should specipy the timestamp: include Mongoid::Timestamps

• Change validation. e.g: :in => ARRAY, will be: validates :name, presence: true, inclusion: { in: ARRAY }

• Change indexes.

• Change order_by format. e.g: MM: Model.all(:order => 'name'). Mongoid: Model.order_by('name ASC')

• Error is a keyword in Mongoid. So if you have a model named Error, you should change it.

• Pagination format is different, using another gem.

• The primary key index entry in MM is id. In Mongoid it's _id, if you have other code relying on .id in the object JSON, you can override as_json function in your Model to create the JSON structure you want.

• In MM, Model.fields(:id, :name) ,limits the fields returned from the database to those supplied to the method. In Mongoid it's Model.only(:name,:id)

• Some queries changes:

  1. Selecting objects by array: MM: Model.where(:attr.in => [ ] ) and Model.where(:attr => [ ] ) . Mongoid is only: Model.where(:attr.in => [ ] )

  2. Map option of MM is equivalent to the Mid's pluck. Model.map(&:name) --to-- Model.pluck(:name)

  3. Mongoid doesn't support find query for nil. e.g: value = nil. Model.find(value) will throw an error : "Calling Document .find with nil is invalid". So in mongoid we should do: Model.find(value || "").

  4. In MM: Model.find_or_initialize_by_name("BOB"). In Mongoid Model.find_or_initialize_by(name: "BOB").

  5. MM can be used in those two options: Model.where({:name => 'BOB'}).first, and also Model.first({:name => 'BOB'}). Mongoid has only first option.

  6. In MM, to update multiple objects: Model.set({conditions},attr_to_update). In Mongoid: Model.where(conditions).update_all(attr_to_update).

Rails and MongoDB with MongoMapper

Changed the Task entity from EmbeddedDocument to Document, and deleted the
validates_associated: task from Project, it's now working updating, adding and
deleting tasks from updating a Project.

Thanks a lot to x1a4 and John Nunemaker for the help :-)

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