dm-aggregates

DataMapper plugin providing support for aggregates, functions on collections and datasets.

It provides the following functions:

count

Count results (given the conditions)

Friend.count # returns count of all friends
Friend.count(:age.gt => 18) # returns count of all friends older then 18
Friend.count(:conditions => [ 'gender = ?', 'female' ]) # returns count of all your female friends
Friend.count(:address) # returns count of all friends with an address (NULL values are not included)
Friend.count(:address, :age.gt => 18) # returns count of all friends with an address that are older then 18
Friend.count(:address, :conditions => [ 'gender = ?', 'female' ]) # returns count of all your female friends with an address

min

Get the lowest value of a property

Friend.min(:age) # returns the age of the youngest friend
Friend.min(:age, :conditions => [ 'gender = ?', 'female' ]) # returns the age of the youngest female friends

max

Get the highest value of a property

Friend.max(:age) # returns the age of the oldest friend
Friend.max(:age, :conditions => [ 'gender = ?', 'female' ]) # returns the age of the oldest female friends

avg

Get the average value of a property

Friend.avg(:age) # returns the average age of friends
Friend.avg(:age, :conditions => [ 'gender = ?', 'female' ]) # returns the average age of the female friends

sum

Get the total value of a property

Friend.sum(:age) # returns total age of all friends
Friend.sum(:age, :conditions => [ 'gender = ?', 'female' ]) # returns the total age of all female friends