FlattenRecord

An ActiveRecord plugin that helps to denormalize your existing ActiveRecord models.

It provides an easier way to denormalize/flatten normalized records, and generation the table schema.

Example

Existing normalized tables

orders	customers	line_items
id	id	id
customer_id	name	description
discount		total
total		order_id

Denormalized table, generated by flatten_record

denormalized_orders
id
order_id
discount
total
customer_id
customer_name
line_item_id
line_item_description
line_item_total
line_items_sum (custom column)
total_in_usd (custom column)

Usage

Add gem dependency

gem 'flatten_record'

Include module in your newly defined model

include FlattenRecord::Flattener

Define denormalization

class DenormalizedOrder < ActiveRecord::Base
    include FlattenRecord::Flattener

    denormalize :order, {

        # specifying association
        include: { 
            # :belongs_to association
            customer: {}

            # :has_many association, create multiple denormalized records  
            line_items: {}

        },

        # save results of methods defined in Normalized model
        methods: {
            total_in_usd: :decimal 
        },

        # compute results of methods defined in Denormalized model
        compute: {
            line_items_sum: { type: :decimal, default: 0 } 
        }
    }

    private
    def compute_line_items_sum(order)
        order.line_items.collect(&:total).inject(:+)
    end
end

class Order < ActiveRecord::Base
    def total_in_usd
        # calculation
    end
end

Generate migration file

Generate migration file based on the definition

$ rails generate flatten_record:migration denormalized_order
  create  db/migrate/20140313034700_create_table_denormalized_orders.rb     

Update definition and generate new migration file

$ rails generate flatten_record:migration denormalized_order
Warning. Table already exists: denormalized_orders
Generating migration based on the difference..
Add columns: line_items_description
  create  db/migrate/20140313034736_add_line_items_description_to_denormalized_orders.rb      

Use denormalizer methods

Create record

irb(main)> DenormalizedOrder.create_with(order)

Deleting record(s)

irb(main)> DenormalizedOrder.destroy_with(order)

Update record(s)

irb(main)> DenormalizedOrder.update_with(order)

API Documentation/Development/Discussion

Refer to the wiki.

Versions

v1

• tree-based denormalization: nicer code & structure √
• new DSL + syntax √
  (Credit to @scottharvey's issue #6)
• added :prefix option - use your own column prefix √
  
• added :methods option - save normalized model's method √
  (Credit to @scottharvey's idea)
• change to old :save option to :compute option √
  (Credit to @scottharvey's idea)
• deprecate observer √
  

v0

• denormalize fields and nested fields √
  
• denormalize belongs_to, has_many typed associations √
  
• generate migration from denormalized model √
  
• observe model changes and update denormalized model √
  

Contributors

• @scottharvey

License

see MIT-LICENSE.