Question

I am developing a system that has folders, groups and permissions. Permissions determine what the different groups can do in each folder. Therefore whenever I create a new group, I want to add a record to the permissions table for each folder, describing what the new group can do in that folder.

Currently I am just looping through all the folders in the system and adding a permissions record for each folder:

group = Group.create(params)

Folder.all.each do |folder|
  Permission.create! do |permission|
    permission.folder = folder
    permission.group = group
    permission.can_create = true
    permission.can_read = true
    permission.can_update = true
    permission.can_delete = true
  end
end

I don’t like the fact that I have to loop through all the records everytime I create a new group. So basically I am looking for an elegant way to execute the following SQL using ActiveRecord.

INSERT INTO permissions (folder_id, group_id, can_creat, can_read, can_update, can_delete)
SELECT id, #{group.id}, true, true, true, true
FROM folders

I guess I could run the above query using find_by_sql, but that doesn’t feel right, cause I am INSERTing, not SELECTing.

Or should I just forget about this and keep looping through my folder records like in the example above?

Thanks in advance.

Answer 1

This is how I deal with custom sql in rails/activerecord (after_create trick included!)

class Group < ActiveRecord::Base
  after_create :create_default_folder_permissions

  def create_default_folder_permissions
    sql = <<-SQL
     INSERT INTO permissions (folder_id, group_id, can_creat, can_read, can_update, can_delete)
        SELECT id, #{id}, true, true, true, true FROM folders
    SQL
    connection.execute(sql)
  end
end

However adding permission for each group and each folder can soon become a bottleneck since you get number_of_groups * number_of_folders rows in permissions table. But if you your queries are simple and indexes right you can easily scale to milions of rows.