discourse/db/migrate/20200409033412_create_bookmarks_from_post_action_bookmarks.rb

# frozen_string_literal: true

class CreateBookmarksFromPostActionBookmarks < ActiveRecord::Migration[6.0]
  def up
    SiteSetting.enable_bookmarks_with_reminders = true

    bookmarks_to_create = []
    loop do
      # post action type id 1 is :bookmark. we do not need to OFFSET here for
      # paging because the WHERE bookmarks.id IS NULL clause handles this effectively,
      # because we do not get bookmarks back that have already been inserted
      post_action_bookmarks = DB.query(
        <<~SQL, type_id: 1
        SELECT post_actions.id, post_actions.post_id, posts.topic_id, post_actions.user_id
        FROM post_actions
        INNER JOIN posts ON posts.id = post_actions.post_id
        LEFT JOIN bookmarks ON bookmarks.post_id = post_actions.post_id AND bookmarks.user_id = post_actions.user_id
        INNER JOIN topics ON topics.id = posts.topic_id
        INNER JOIN users ON users.id = post_actions.user_id
        WHERE bookmarks.id IS NULL AND post_action_type_id = :type_id AND post_actions.deleted_at IS NULL AND posts.deleted_at IS NULL
        LIMIT 2000
        SQL
      )
      break if post_action_bookmarks.count.zero?

      post_action_bookmarks.each do |pab|
        now = Time.zone.now
        bookmarks_to_create << "(#{pab.topic_id}, #{pab.post_id}, #{pab.user_id}, '#{now}', '#{now}')"
      end

      create_bookmarks(bookmarks_to_create)
      bookmarks_to_create = []
    end # loop
  end

  def down
    raise ActiveRecord::IrreversibleMigration
  end

  def create_bookmarks(bookmarks_to_create)
    return if bookmarks_to_create.empty?

    # this will ignore conflicts in the bookmarks table so
    # if the user already has a post bookmarked in the new way,
    # then we don't error and keep on truckin'
    #
    # we shouldn't have duplicates here at any rate because of
    # the above LEFT JOIN but best to be safe knowing this
    # won't blow up
    #
    DB.exec(
      <<~SQL
      INSERT INTO bookmarks (topic_id, post_id, user_id, created_at, updated_at)
      VALUES #{bookmarks_to_create.join(",\n")}
      ON CONFLICT DO NOTHING
      SQL
    )
  end
end