module ActiveRecord module Calculations #:nodoc: extend ActiveSupport::Concern CALCULATIONS_OPTIONS = [:conditions, :joins, :order, :select, :group, :having, :distinct, :limit, :offset, :include, :from] module ClassMethods # Count operates using three different approaches. # # * Count all: By not passing any parameters to count, it will return a count of all the rows for the model. # * Count using column: By passing a column name to count, it will return a count of all the rows for the model with supplied column present # * Count using options will find the row count matched by the options used. # # The third approach, count using options, accepts an option hash as the only parameter. The options are: # # * :conditions: An SQL fragment like "administrator = 1" or [ "user_name = ?", username ]. See conditions in the intro to ActiveRecord::Base. # * :joins: Either an SQL fragment for additional joins like "LEFT JOIN comments ON comments.post_id = id" (rarely needed) # or named associations in the same form used for the :include option, which will perform an INNER JOIN on the associated table(s). # If the value is a string, then the records will be returned read-only since they will have attributes that do not correspond to the table's columns. # Pass :readonly => false to override. # * :include: Named associations that should be loaded alongside using LEFT OUTER JOINs. The symbols named refer # to already defined associations. When using named associations, count returns the number of DISTINCT items for the model you're counting. # See eager loading under Associations. # * :order: An SQL fragment like "created_at DESC, name" (really only used with GROUP BY calculations). # * :group: An attribute name by which the result should be grouped. Uses the GROUP BY SQL-clause. # * :select: By default, this is * as in SELECT * FROM, but can be changed if you, for example, want to do a join but not # include the joined columns. # * :distinct: Set this to true to make this a distinct calculation, such as SELECT COUNT(DISTINCT posts.id) ... # * :from - By default, this is the table name of the class, but can be changed to an alternate table name (or even the name # of a database view). # # Examples for counting all: # Person.count # returns the total count of all people # # Examples for counting by column: # Person.count(:age) # returns the total count of all people whose age is present in database # # Examples for count with options: # Person.count(:conditions => "age > 26") # Person.count(:conditions => "age > 26 AND job.salary > 60000", :include => :job) # because of the named association, it finds the DISTINCT count using LEFT OUTER JOIN. # Person.count(:conditions => "age > 26 AND job.salary > 60000", :joins => "LEFT JOIN jobs on jobs.person_id = person.id") # finds the number of rows matching the conditions and joins. # Person.count('id', :conditions => "age > 26") # Performs a COUNT(id) # Person.count(:all, :conditions => "age > 26") # Performs a COUNT(*) (:all is an alias for '*') # # Note: Person.count(:all) will not work because it will use :all as the condition. Use Person.count instead. def count(*args) case args.size when 0 construct_calculation_arel({}, current_scoped_methods).count when 1 if args[0].is_a?(Hash) options = args[0] distinct = options.has_key?(:distinct) ? options.delete(:distinct) : false construct_calculation_arel(options, current_scoped_methods).count(options[:select], :distinct => distinct) else construct_calculation_arel({}, current_scoped_methods).count(args[0]) end when 2 column_name, options = args distinct = options.has_key?(:distinct) ? options.delete(:distinct) : false construct_calculation_arel(options, current_scoped_methods).count(column_name, :distinct => distinct) else raise ArgumentError, "Unexpected parameters passed to count(): #{args.inspect}" end rescue ThrowResult 0 end # Calculates the average value on a given column. The value is returned as # a float, or +nil+ if there's no row. See +calculate+ for examples with # options. # # Person.average('age') # => 35.8 def average(column_name, options = {}) calculate(:average, column_name, options) end # Calculates the minimum value on a given column. The value is returned # with the same data type of the column, or +nil+ if there's no row. See # +calculate+ for examples with options. # # Person.minimum('age') # => 7 def minimum(column_name, options = {}) calculate(:minimum, column_name, options) end # Calculates the maximum value on a given column. The value is returned # with the same data type of the column, or +nil+ if there's no row. See # +calculate+ for examples with options. # # Person.maximum('age') # => 93 def maximum(column_name, options = {}) calculate(:maximum, column_name, options) end # Calculates the sum of values on a given column. The value is returned # with the same data type of the column, 0 if there's no row. See # +calculate+ for examples with options. # # Person.sum('age') # => 4562 def sum(column_name, options = {}) calculate(:sum, column_name, options) end # This calculates aggregate values in the given column. Methods for count, sum, average, minimum, and maximum have been added as shortcuts. # Options such as :conditions, :order, :group, :having, and :joins can be passed to customize the query. # # There are two basic forms of output: # * Single aggregate value: The single value is type cast to Fixnum for COUNT, Float for AVG, and the given column's type for everything else. # * Grouped values: This returns an ordered hash of the values and groups them by the :group option. It takes either a column name, or the name # of a belongs_to association. # # values = Person.maximum(:age, :group => 'last_name') # puts values["Drake"] # => 43 # # drake = Family.find_by_last_name('Drake') # values = Person.maximum(:age, :group => :family) # Person belongs_to :family # puts values[drake] # => 43 # # values.each do |family, max_age| # ... # end # # Options: # * :conditions - An SQL fragment like "administrator = 1" or [ "user_name = ?", username ]. See conditions in the intro to ActiveRecord::Base. # * :include: Eager loading, see Associations for details. Since calculations don't load anything, the purpose of this is to access fields on joined tables in your conditions, order, or group clauses. # * :joins - An SQL fragment for additional joins like "LEFT JOIN comments ON comments.post_id = id". (Rarely needed). # The records will be returned read-only since they will have attributes that do not correspond to the table's columns. # * :order - An SQL fragment like "created_at DESC, name" (really only used with GROUP BY calculations). # * :group - An attribute name by which the result should be grouped. Uses the GROUP BY SQL-clause. # * :select - By default, this is * as in SELECT * FROM, but can be changed if you for example want to do a join, but not # include the joined columns. # * :distinct - Set this to true to make this a distinct calculation, such as SELECT COUNT(DISTINCT posts.id) ... # # Examples: # Person.calculate(:count, :all) # The same as Person.count # Person.average(:age) # SELECT AVG(age) FROM people... # Person.minimum(:age, :conditions => ['last_name != ?', 'Drake']) # Selects the minimum age for everyone with a last name other than 'Drake' # Person.minimum(:age, :having => 'min(age) > 17', :group => :last_name) # Selects the minimum age for any family without any minors # Person.sum("2 * age") def calculate(operation, column_name, options = {}) construct_calculation_arel(options, current_scoped_methods).calculate(operation, column_name, options.slice(:distinct)) rescue ThrowResult 0 end private def validate_calculation_options(options = {}) options.assert_valid_keys(CALCULATIONS_OPTIONS) end def construct_calculation_arel(options = {}, merge_with_relation = nil) validate_calculation_options(options) options = options.except(:distinct) merge_with_includes = merge_with_relation ? merge_with_relation.includes_values : [] includes = (merge_with_includes + Array.wrap(options[:include])).uniq if includes.any? merge_with_joins = merge_with_relation ? merge_with_relation.joins_values : [] joins = (merge_with_joins + Array.wrap(options[:joins])).uniq join_dependency = ActiveRecord::Associations::ClassMethods::JoinDependency.new(self, includes, construct_join(joins)) construct_calculation_arel_with_included_associations(options, join_dependency, merge_with_relation) else relation = unscoped.apply_finder_options(options.slice(:joins, :conditions, :order, :limit, :offset, :group, :having)) if merge_with_relation relation = merge_with_relation.except(:select, :order, :limit, :offset, :group, :from).merge(relation) end from = merge_with_relation.from_value if merge_with_relation && merge_with_relation.from_value.present? from = options[:from] if from.blank? && options[:from].present? relation = relation.from(from) select = options[:select].presence || (merge_with_relation ? merge_with_relation.select_values.join(", ") : nil) relation = relation.select(select) relation end end def construct_calculation_arel_with_included_associations(options, join_dependency, merge_with_relation = nil) relation = unscoped for association in join_dependency.join_associations relation = association.join_relation(relation) end if merge_with_relation relation.joins_values = (merge_with_relation.joins_values + relation.joins_values).uniq relation.where_values = merge_with_relation.where_values merge_limit = merge_with_relation.taken end relation = relation.apply_finder_options(options.slice(:joins, :group, :having, :order, :conditions, :from)). select(column_aliases(join_dependency)) if !using_limitable_reflections?(join_dependency.reflections) && (merge_limit || options[:limit]) relation = relation.where(construct_arel_limited_ids_condition(options, join_dependency)) end relation = relation.limit(options[:limit] || merge_limit) if using_limitable_reflections?(join_dependency.reflections) relation end end end end