CODEWITHSUNDEEP
ruby-on-railsruby
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Reputation: 1680

Ruby on Rails - multiple database connections

I'm developing an application where it lets users to establish many number of database connections with a has-many relationship between user and connections. The connections are passive until the user manually connects each. The motive is to perform queries on them, parallely.

I don't find good tutorials related to this, can you help me with some tips on how to accomplish this ?

Upvotes: 0

Views: 3006

Answers (3)

Coding active
Coding active

Reputation: 1680

After researching for a bit, turns out there's a much simpler approach using ActiveRecord Connection pool.

  1. Setup a relationship between users and the database connections, in this case user 1 .. n connections.

  2. Make sure the model record can individually connect using 

    obj = ActiveRecord::Base.establish_connection(...spec...) 

obj.connection.exec_query("Select * from users") 
# the response is in the form of ActiveResult, which allows flexible operations around the result.

  3. Close the connection once done with the database.

References:

http://api.rubyonrails.org/classes/ActiveRecord/ConnectionAdapters/ConnectionHandler.html

http://api.rubyonrails.org/classes/ActiveRecord/ConnectionAdapters/ConnectionPool.html

Upvotes: 2

peter
peter

Reputation: 42182

Assuming you want to use activerecord you can go two ways:

Here an example how to use such a model, the class_name parameter is the name of the model to be used. It's from a Sinatra app but I'm sure you'll be able to adapt it for Rails. It's a backend for a ExtJs javascript app using multiple models expecting JSON as result.

 # controller

%w(create read update destroy).each do |action|
  [:get, :post].each do |method|
      send(method, "/path/#{action}") do
        response.headers['Access-Control-Allow-Origin'] = '*'
        content_type :json
        if params[:store]
          store = Object.const_get(params[:store]) 
        else
          store = Signal
        end
        resp = send(action, store, params)
        jsonp(resp)
      end
  end
end

# in helper.rb

def read (class_name, params)
  params = params.symbolize_keys
  default = {store: 'Signaal', limit: 10, sort: 'id', order: 'ASC', start: 0, user: '0'}
  params = default.merge params
  generic_data_getter(class_name, params, params[:start], params[:limit], params[:sort], params[:dir])
end

def generic_data_getter (class_name, params, start=0, limit=10, sort='id', dir='ASC')
  selection = build_selection(class_name, params)
  data = class_name.where(selection).offset(start).limit(limit).order("#{sort} #{dir}")
  {:success => true, :totalCount => data.except(:offset, :limit, :order).count, :result => data.as_json}
end

If not or for simple predefined searches or speed you can connect and disconnect as a connection is needed. Here an example for Oracle.

require 'oci8'
CONN = OCI8.new('scheme','password','dbserver')
sql = '....'
CONN.exec(sql) {|record|puts record.join(',')}
CONN.logoff

Be aware of malicius use like code injection.

Upvotes: 1

Goko Gorgiovski
Goko Gorgiovski

Reputation: 1462

For my application I use this gem

https://github.com/thiagopradi/octopus

have good documentation and examples.

Upvotes: 1

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