redmine/db/migrate/20161010081528_change_journal_details_value_limit.rb

class ChangeJournalDetailsValueLimit < ActiveRecord::Migration
  def up
    if ActiveRecord::Base.connection.adapter_name =~ /mysql/i
      max_size = 16.megabytes
      change_column :journal_details, :value, :text, :limit => max_size
      change_column :journal_details, :old_value, :text, :limit => max_size
    end
  end

  def down
    # no-op
  end
end