ActiveRecord Import with SQL server

Question

I am trying to insert 5.6m rows into SQLserver db from a ruby script and finding the fastest way. First solution was to write a SQL Insert statement and pass values inside like

("INSERT INTO fct_coupons_distributed (coupon_campaign_id, coupon_unique_code) VALUES #{batchData}"

but as i am using TinyTDS the limit is 1000 rows at a time. (suggest me if i can fix it any how. i would like 35k rows at a time in one SQL)

The second way i tried is using ActiveRecord Import gem which i am having problems with. so my data is in loop and after the first batch insertion it gives me an error like

ArgumentError: struct size differs

Ruby Script:

  def create_coupons
    campaign = [483, 482]
    start_at = Time.now
    puts start_at
    column = [:coupon_campaign_id, :coupon_unique_code]
    batchData = []
    campaign.each_with_index do |camp_id, index|
      puts "-----------------------------#{index + 1}/80-----------------------------------------"
      70000.times do
        coupon_code = ([*('A'..'Z'),*('0'..'9')]-%w(0 1 I O)).sample(12).join
        batchData << [camp_id, coupon_code]
      end
      FctCoupon.import column, batchData
    end
    puts "start_at: #{start_at}"
    puts "end_at: #{Time.now}"
  end

so the problem here is that it inserts all 70k rows for the first loop but when the second loop happens for my campaign id it just gives me an error saying ArgumentError: struct size differs

same if i mention a batch_size FctCoupon.import column, batchData, batch_size: 35000 after inserting 35k rows it give the same error