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class AddUniqueIndexOnCustomFieldsTrackers < ActiveRecord::Migration

  def up

    table_name = "#{CustomField.table_name_prefix}custom_fields_trackers#{CustomField.table_name_suffix}"

    duplicates = CustomField.connection.select_rows("SELECT custom_field_id, tracker_id FROM #{table_name} GROUP BY custom_field_id, tracker_id HAVING COUNT(*) > 1")

    duplicates.each do |custom_field_id, tracker_id|

      # Removes duplicate rows

      CustomField.connection.execute("DELETE FROM #{table_name} WHERE custom_field_id=#{custom_field_id} AND tracker_id=#{tracker_id}")

      # And insert one

      CustomField.connection.execute("INSERT INTO #{table_name} (custom_field_id, tracker_id) VALUES (#{custom_field_id}, #{tracker_id})")

    end

    if index_exists? :custom_fields_trackers, [:custom_field_id, :tracker_id]

      remove_index :custom_fields_trackers, [:custom_field_id, :tracker_id]

    end

    add_index :custom_fields_trackers, [:custom_field_id, :tracker_id], :unique => true

  end

  def down

    if index_exists? :custom_fields_trackers, [:custom_field_id, :tracker_id]

      remove_index :custom_fields_trackers, [:custom_field_id, :tracker_id]

    end

    add_index :custom_fields_trackers, [:custom_field_id, :tracker_id]

  end

end