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@asosori2

ruby(rails)でデータ量が多い時でもcsvファイルを比較的速く作成する書き方

More than 1 year has passed since last update.

メモなので分かりにくいかもです

user_data_csv = CSV.generate do |csv|
  csv_column_names = ["名前", "年齢"]
  csv << csv_column_names

  User.all.find_each do |user|
    csv << [user.name, user.age]
  end
end

File.open("all_user_data.csv", "w") do |csv| 
  csv.puts user_data_csv
end

データをまとめてからcsvファイルに書き出してるので、こう書くより速い

CSV.open('all_user_data.csv','w') do |csv|
  csv_column_names = ["名前", "年齢"]
  csv << csv_column_names

  User.all.find_each do |user|
    csv << [user.name, user.age]
  end
end

こちらにさらにいいやり方が載っていました。
https://www.techscore.com/blog/2017/12/04/fast_and_low-load_processing_method_when_exporting_csv_from_db_with_rails/

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