Mondrian

A ruby DSL based off of https://github.com/rsim/mondrian-olap.

This gem only consists of the schema definition and not the olap server itself. It is not dependent on jruby.

Installation

Add this line to your application's Gemfile:

gem 'mondrian'

And then execute:

$ bundle

Or install it yourself as:

$ gem install mondrian

Usage

Schema definition

At first you need to define OLAP schema mapping to relational database schema tables and columns. OLAP schema consists of:

• Cubes

Multidimensional cube is a collection of measures that can be accessed by dimensions. In relational database cubes are stored in fact tables with measure columns and dimension foreign key columns.

• Dimensions

Dimension can be used in one cube (private) or in many cubes (shared). In relational database dimensions are stored in dimension tables.

• Hierarchies and levels

Dimension has at least one primary hierarchy and optional additional hierarchies and each hierarchy has one or more levels. In relational database all levels can be stored in the same dimension table as different columns or can be stored also in several tables.

• Members

Dimension hierarchy level values are called members.

• Measures

Measures are values which can be accessed at detailed level or aggregated (e.g. as sum or average) at higher dimension hierarchy levels. In relational database measures are stored as columns in cube table.

• Calculated measures

Calculated measures are not stored in database but calculated using specified formula from other measures.

Read more about about defining Mondrian OLAP schema.

Here is example how to define OLAP schema and its mapping to relational database tables and columns using mondrian-olap:

require "rubygems"
require "mondrian"

schema = Mondrian::Schema.define do
  cube 'Sales' do
    table 'sales'
    dimension 'Customers', :foreign_key => 'customer_id' do
      hierarchy :has_all => true, :all_member_name => 'All Customers', :primary_key => 'id' do
        table 'customers'
        level 'Country', :column => 'country', :unique_members => true
        level 'State Province', :column => 'state_province', :unique_members => true
        level 'City', :column => 'city', :unique_members => false
        level 'Name', :column => 'fullname', :unique_members => true
      end
    end
    dimension 'Products', :foreign_key => 'product_id' do
      hierarchy :has_all => true, :all_member_name => 'All Products',
                :primary_key => 'id', :primary_key_table => 'products' do
        join :left_key => 'product_class_id', :right_key => 'id' do
          table 'products'
          table 'product_classes'
        end
        level 'Product Family', :table => 'product_classes', :column => 'product_family', :unique_members => true
        level 'Brand Name', :table => 'products', :column => 'brand_name', :unique_members => false
        level 'Product Name', :table => 'products', :column => 'product_name', :unique_members => true
      end
    end
    dimension 'Time', :foreign_key => 'time_id', :type => 'TimeDimension' do
      hierarchy :has_all => false, :primary_key => 'id' do
        table 'time'
        level 'Year', :column => 'the_year', :type => 'Numeric', :unique_members => true, :level_type => 'TimeYears'
        level 'Quarter', :column => 'quarter', :unique_members => false, :level_type => 'TimeQuarters'
        level 'Month', :column => 'month_of_year', :type => 'Numeric', :unique_members => false, :level_type => 'TimeMonths'
      end
      hierarchy 'Weekly', :has_all => false, :primary_key => 'id' do
        table 'time'
        level 'Year', :column => 'the_year', :type => 'Numeric', :unique_members => true, :level_type => 'TimeYears'
        level 'Week', :column => 'weak_of_year', :type => 'Numeric', :unique_members => false, :level_type => 'TimeWeeks'
      end
    end
    measure 'Unit Sales', :column => 'unit_sales', :aggregator => 'sum'
    measure 'Store Sales', :column => 'store_sales', :aggregator => 'sum'
  end
end

Contributing

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Added some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create new Pull Request