Ruby skip existing record while importing csv

Question

My problem is that i have to export an excel sheet save some rows to the database without duplication or redundancy so i started it with importing CSV instead of XLS then when i finish i might be able to parse the xls this is my model code:

require 'csv'
class Machine < ActiveRecord::Base
  def self.assign_row(row)
  a, b, c, d = row
  @c = c.slice(1,4)
 Machine.create(name: c, mid: @c)
   end
 def self.import(file)
 CSV.foreach(file.path) do |row|
  machine = Machine.assign_row(row)
    end
  end
 end

Import method in machines_controller

 def import
 count = Machine.import params[:file]
 redirect_to machines_path, notice: "file imported successfully!"
  end

Migration code

 def change
 create_table :machines do |t|
 t.string :name
 t.string :mid
 t.timestamps null: false
 end
  add_index :machines, :name, :unique => true
 end

and the view code

 <%= form_tag import_machines_path, multipart: true do %>
 <%= file_field_tag :file %>
 <%= submit_tag "upload" %>
 <% end %>

routes

  Rails.application.routes.draw do
 resources :errors
 resources :machines do
  collection do
     post :import
    end
   end
  root "machines#index
   end

any thoughts on how to skip duplicated records from saving into database would be appreciated thanks

harika · Accepted Answer · 2017-08-22 21:36:28Z

1

Unique Identifier: To avoid duplicate records saving to database you should maintain a unique identifier other than primary key. This helps you to identify if the record already available in DB, if it is available you can skip that record from saving again.

I guess you can use name in this case, which should be unique for each record in database. write a uniqueness validation in model to implement this.

After changes:

 validates_uniqueness_of  :name

 def self.assign_row(row)
   a, b, c, d = row
   @c = c.slice(1,4)
   machine = Machine.find_by(name: c)
   Machine.create(name: c, mid: @c) if machine.blank?
 end

Hope it helps!! Thank you.

edited Aug 22, 2017 at 21:36

answered Aug 22, 2017 at 19:35

harika

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4 Comments

amreos Over a year ago

Thank you for your response i did that however i got this error NoMethodError in MachinesController#import undefined method `import' for #<Class:0x007fcb7c171638>

harika Over a year ago

In your controller, change the line count = Machine.import params[:file] to count = Machine.import(params[:file])

harika Over a year ago

I have edited my answer as you have defined name as unique in your migration. Please check

amreos Over a year ago

Thank you , you had saved me.

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