Statistics
This ActiverRecord plugin allows you to easily define and pull statistics for AR models. This plugin was built with reporting in mind.
Announcements
- Bug: There is a bug in Rails 2.x where grouping by multiple fields results in wrong values for calculations. I have created a patch for this bug, please encourage the fix by giving feedback or giving +1 plus a short supportive comment. The patch lives here: https://rails.lighthouseapp.com/projects/8994/tickets/5182-activerecordcalculations-returns-incorrect-data-when-grouping-by-multiple-fields.
Installation
gem install statistics
OR script/plugin install git://github.com/acatighera/statistics.git
Examples
Defining statistics is similar to defining named scopes. Strings and symbols both work as names.
class Account < ActiveRecord::Base
define_statistic :user_count, :count => :all
define_statistic :average_age, :average => :all, :column_name => 'age'
define_statistic 'subscriber count', :count => :all, :conditions => "subscription_opt_in = 1"
end
class Donations < ActiveRecord::Base
define_statistic :total_donations, :sum => :all, :column_name => "amount"
end
Actually pulling the numbers is simple:
#####for all stats
Account.statistics # returns { :user_count => 120, :average_age => 28, 'subscriber count' => 74 }
#####for a single stat
Account.get_stat(:user_count) # returns 120
Here are some additional benefits of using this plugin:
Easily Filter
Note: I found filtering to be an important part of reporting (ie. filtering by date). All filters are optional so even if you define them you don’t have to use them when pulling data. Using the filter_all_stats_on
method and :joins
options you can make things filterable by the same things which I found to be extremely useful.
class Account < ActiveRecord::Base
define_statistic :user_count, :count => :all, :filter_on => { :state => 'state = ?', :created_after => 'DATE(created_at) > ?'}
define_statistic :subscriber_count, :count => :all, :conditions => "subscription_opt_in = true"
filter_all_stats_on(:account_type, "account_type = ?")
end
Account.statistics(:account_type => 'non-admin')
Account.get_stat(:user_count, :account_type => 'non-admin', :created_after => ‘2009-01-01’, :state => 'NY')
# NOTE: filters are optional (ie. no filters will be applied if none are passed in)
Account.get_stat(:user_count)
Caching
This is a new feature that uses Rails.cache
. You can cache certain statistics for a specified amount of time (see below). By default caching is disabled if you do not pass in the :cache_for
option. It is also important to note that caching is scoped by filters, there is no way around this since different filters produce different values.
class Account < ActiveRecord::Base
define_statistic :user_count, :count => :all, :cache_for => 30.minutes, :filter_on { :state => 'state = ?' }
end
Account.statistics(:state => 'NY') # This call generates a SQL query
Account.statistics(:state => 'NY') # This call and subsequent calls for the next 30 minutes will use the cached value
Account.statistics(:state => 'PA') # This call generates a SQL query because the user count for NY and PA could be different (and probably is)
Note: If you want Rails.cache to work properly, you need to use mem_cache_store in your rails enviroment file (ie. config.cache_store = :mem_cache_store
in your enviroment.rb file).
Standardized
All ActiveRecord classes now respond to statistics
and get_stat
methods
all_stats = []
[ Account, Post, Comment ].each do |ar|
all_stats << ar.statistics
end
Calculated statistics (DRY)
You can define calculated metrics in order to perform mathematical calculations on one or more defined statistics.
class Account < ActiveRecord::Base
has_many :donations
define_statistic :user_count, :count => :all
define_statistic :total_donations, :sum => :all, :column_name => 'donations.amount', :joins => :donations
define_calculated_statistic :average_donation_per_user do
defined_stats(:total_donations) / defined_stats(:user_count)
end
filter_all_stats_on(:account_type, "account_type = ?")
filter_all_stats_on(:state, "state = ?")
filter_all_stats_on(:created_after, "DATE(created_at) > ?")
end
Pulling stats for calculated metrics is the same as for regular statistics. They also work with filters like regular statistics!
Account.get_stat(:average_donation_per_user, :account_type => 'non-admin', :state => 'NY')
Account.get_stat(:average_donation_per_user, :created_after => '2009-01-01')
Reuse scopes you already have defined
You can reuse the code you have written to do reporting.
class Account < ActiveRecord::Base
has_many :posts
named_scope :not_admins, :conditions => “account_type = ‘non-admin’”
named_scope :accounts_with_posts, :joins => :posts
define_statistic :active_users_count, :count => [:not_admins, :accounts_with_posts]
end
Accepts all ActiveRecord::Calculations options
The :conditions
and :joins
options are all particularly useful
class Account < ActiveRecord::Base
has_many :posts
define_statistic :active_users_count, :count => :all, :joins => :posts, :conditions => "account_type = 'non-admin'"
end