Need help converting query from sqlite to postgresql

My rails scope is not working on heroku due to sqlite and postgresql database difference on development and production/heroku

I have following scope working on my development

#conversations_controller    
scope :between, -> (sender_id,recipient_id) do
        where("(conversations.sender_id = ? AND conversations.recipient_id =?) OR (conversations.sender_id = ? AND conversations.recipient_id =?)", sender_id,recipient_id, recipient_id, sender_id)
      end

scope :involving, -> (user) do
    where("conversations.sender_id =? OR conversations.recipient_id =?",user.id,user.id)
  end

i need its equivalent for postgresql

The error i'm getting is

An ActiveRecord::StatementInvalid occurred in conversations#create:

  PG::UndefinedTable: ERROR:  relation "conversations" does not exist
LINE 1: SELECT "conversations".* FROM "conversations" WHERE ((conver...
                                      ^
: SELECT "conversations".* FROM "conversations" WHERE ((conversations.sender_id = '1' AND conversations.recipient_id ='6') OR (conversations.sender_id = '6' AND conversations.recipient_id ='1'))
  app/controllers/conversations_controller.rb:5:in `create'

P.S. 'heroku run rake db:migrate' was timing out so i ran 'heroku run:detached rake db:migrate' , does that make any difference ?

Thanks in advance !