note_code.rb

# Arel 
#"ROW_NUMBER() OVER ()"
row_nubmer = Arel::Nodes::NamedFunction.new('ROW_NUMBER', [] )
sql = Arel::Nodes::Over.new(row_number).as('row_number')
row_nubmer.over.as('row_number')

table = Arel::Table.new :users
# COUNT("users"."id") OVER () AS foo
table[:id].count.over.as('foo') 

# array_agg
func = ->(){ Arel::Nodes::NamedFunction.new('array_agg', [self]) }
Arel::Attributes::Attribute.send :define_method, :array_agg, func

Loan.group(:state).calculate(:array_agg, :id)
# SELECT array_agg("loans"."id") AS array_agg_id, state AS state FROM "loans"  GROUP BY "loans"."state"

# Phone Validation
validates :phone, :format => {
 :with => /(\+7)|8(\s){0,1}(\d){3,3}(\-|\_\s){0,1}(\d){3,3}(\-|\_\s){0,1}(\d){2,2}(\-|\_\s){0,1}(\d){2}/ 
}

# application
  rescue_from(ActiveRecord::RecordNotFound, :with => :record_not_found) 
  rescue_from(ActionController::RoutingError, :with => :path_not_found) 
  rescue_from(RoleBase::AccessDenied, :with => :record_not_found)       

def record_not_found; end 
def path_not_found; end 

# put this in config/initializer/fields_with_errors.rb
ActionView::Base.field_error_proc = Proc.new do |html_tag, instance|
  if html_tag =~ /<(input|label|textarea|select)/
    %{<div class="field_with_errors">#{html_tag}<label for="#{instance.send(:tag_id)}" class="message">#{instance.error_message.first}</label> </div>}.html_safe
  else
    html_tag
  end
end

# Hstore
# Find all products that have a key of 'author' in data
Product.where("data ? :key", :key => 'author')

# Find all products that have a 'pages' and '368' key value pair in data
Product.where("data @> (:key => :value)", :key => 'pages', :value => '368')

# Find all products that don't have a key value pair 'pages' and '999' in data
Product.where("not data @> (:key => :value)", :key => 'pages', :value => '999')

# Find all products having key 'author' and value like 'ba' in data
Product.where("data -> :key iLIKE :value", :key => 'author', :value => "%KitKat%")

# Expiration
response.headers["Expires"] = 1.year.from_now.httpdate

# Gem commands
require 'rubygems'
gem = Gem::GemRunner.new
gem.run(['help','commands'])