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) calculate(:count, *construct_count_options_from_args(*args)) 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 = {}) validate_calculation_options(operation, options) operation = operation.to_s.downcase scope = scope(:find) merged_includes = merge_includes(scope ? scope[:include] : [], options[:include]) if operation == "count" if merged_includes.any? distinct = true column_name = options[:select] || primary_key end distinct = nil if column_name.to_s =~ /\s*DISTINCT\s+/i distinct ||= options[:distinct] else distinct = nil end catch :invalid_query do relation = if merged_includes.any? join_dependency = ActiveRecord::Associations::ClassMethods::JoinDependency.new(self, merged_includes, construct_join(options[:joins], scope)) construct_finder_arel_with_included_associations(options, join_dependency) else relation = arel_table(options[:from]). joins(construct_join(options[:joins], scope)). where(construct_conditions(options[:conditions], scope)). order(options[:order]). limit(options[:limit]). offset(options[:offset]) end if options[:group] return execute_grouped_calculation(operation, column_name, options, relation) else return execute_simple_calculation(operation, column_name, options.merge(:distinct => distinct), relation) end end 0 end def execute_simple_calculation(operation, column_name, options, relation) #:nodoc: column = if column_names.include?(column_name.to_s) Arel::Attribute.new(arel_table(options[:from] || table_name), options[:select] || column_name) else Arel::SqlLiteral.new(options[:select] || (column_name == :all ? "*" : column_name.to_s)) end relation = relation.select(operation == 'count' ? column.count(options[:distinct]) : column.send(operation)) type_cast_calculated_value(connection.select_value(relation.to_sql), column_for(column_name), operation) end def execute_grouped_calculation(operation, column_name, options, relation) #:nodoc: group_attr = options[:group].to_s association = reflect_on_association(group_attr.to_sym) associated = association && association.macro == :belongs_to # only count belongs_to associations group_field = associated ? association.primary_key_name : group_attr group_alias = column_alias_for(group_field) group_column = column_for group_field options[:group] = connection.adapter_name == 'FrontBase' ? group_alias : group_field aggregate_alias = column_alias_for(operation, column_name) options[:select] = (operation == 'count' && column_name == :all) ? "COUNT(*) AS count_all" : Arel::Attribute.new(arel_table, column_name).send(operation).as(aggregate_alias).to_sql options[:select] << ", #{group_field} AS #{group_alias}" relation = relation.select(options[:select]).group(construct_group(options[:group], options[:having], nil)) calculated_data = connection.select_all(relation.to_sql) if association key_ids = calculated_data.collect { |row| row[group_alias] } key_records = association.klass.base_class.find(key_ids) key_records = key_records.inject({}) { |hsh, r| hsh.merge(r.id => r) } end calculated_data.inject(ActiveSupport::OrderedHash.new) do |all, row| key = type_cast_calculated_value(row[group_alias], group_column) key = key_records[key] if associated value = row[aggregate_alias] all[key] = type_cast_calculated_value(value, column_for(column_name), operation) all end end protected def construct_count_options_from_args(*args) options = {} column_name = :all # We need to handle # count() # count(:column_name=:all) # count(options={}) # count(column_name=:all, options={}) # selects specified by scopes case args.size when 0 column_name = scope(:find)[:select] if scope(:find) when 1 if args[0].is_a?(Hash) column_name = scope(:find)[:select] if scope(:find) options = args[0] else column_name = args[0] end when 2 column_name, options = args else raise ArgumentError, "Unexpected parameters passed to count(): #{args.inspect}" end [column_name || :all, options] end private def validate_calculation_options(operation, options = {}) options.assert_valid_keys(CALCULATIONS_OPTIONS) end # Converts the given keys to the value that the database adapter returns as # a usable column name: # # column_alias_for("users.id") # => "users_id" # column_alias_for("sum(id)") # => "sum_id" # column_alias_for("count(distinct users.id)") # => "count_distinct_users_id" # column_alias_for("count(*)") # => "count_all" # column_alias_for("count", "id") # => "count_id" def column_alias_for(*keys) table_name = keys.join(' ') table_name.downcase! table_name.gsub!(/\*/, 'all') table_name.gsub!(/\W+/, ' ') table_name.strip! table_name.gsub!(/ +/, '_') connection.table_alias_for(table_name) end def column_for(field) field_name = field.to_s.split('.').last columns.detect { |c| c.name.to_s == field_name } end def type_cast_calculated_value(value, column, operation = nil) case operation when 'count' then value.to_i when 'sum' then type_cast_using_column(value || '0', column) when 'average' then value && (value.is_a?(Fixnum) ? value.to_f : value).to_d else type_cast_using_column(value, column) end end def type_cast_using_column(value, column) column ? column.type_cast(value) : value end end end end