diff options
Diffstat (limited to 'activerecord/lib/active_record/relation/calculations.rb')
-rw-r--r-- | activerecord/lib/active_record/relation/calculations.rb | 85 |
1 files changed, 43 insertions, 42 deletions
diff --git a/activerecord/lib/active_record/relation/calculations.rb b/activerecord/lib/active_record/relation/calculations.rb index 3b7f7ca151..8b9367acc7 100644 --- a/activerecord/lib/active_record/relation/calculations.rb +++ b/activerecord/lib/active_record/relation/calculations.rb @@ -14,33 +14,34 @@ module ActiveRecord # Person.distinct.count(:age) # # => counts the number of different age values # - # If +count+ is used with +group+, it returns a Hash whose keys represent the aggregated column, + # If #count is used with {Relation#group}[rdoc-ref:QueryMethods#group], + # it returns a Hash whose keys represent the aggregated column, # and the values are the respective amounts: # # Person.group(:city).count # # => { 'Rome' => 5, 'Paris' => 3 } # - # If +count+ is used with +group+ for multiple columns, it returns a Hash whose + # If #count is used with {Relation#group}[rdoc-ref:QueryMethods#group] for multiple columns, it returns a Hash whose # keys are an array containing the individual values of each column and the value - # of each key would be the +count+. + # of each key would be the #count. # # Article.group(:status, :category).count # # => {["draft", "business"]=>10, ["draft", "technology"]=>4, # ["published", "business"]=>0, ["published", "technology"]=>2} # - # If +count+ is used with +select+, it will count the selected columns: + # If #count is used with {Relation#select}[rdoc-ref:QueryMethods#select], it will count the selected columns: # # Person.select(:age).count # # => counts the number of different age values # - # Note: not all valid +select+ expressions are valid +count+ expressions. The specifics differ + # Note: not all valid {Relation#select}[rdoc-ref:QueryMethods#select] expressions are valid #count expressions. The specifics differ # between databases. In invalid cases, an error from the database is thrown. def count(column_name = nil) calculate(:count, column_name) end # Calculates the average value on a given column. Returns +nil+ if there's - # no row. See +calculate+ for examples with options. + # no row. See #calculate for examples with options. # # Person.average(:age) # => 35.8 def average(column_name) @@ -49,7 +50,7 @@ module ActiveRecord # 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. + # #calculate for examples with options. # # Person.minimum(:age) # => 7 def minimum(column_name) @@ -58,7 +59,7 @@ module ActiveRecord # 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. + # #calculate for examples with options. # # Person.maximum(:age) # => 93 def maximum(column_name) @@ -66,46 +67,46 @@ module ActiveRecord 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. + # 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(*args) - return super if block_given? - calculate(:sum, *args) + def sum(column_name = nil, &block) + return super(&block) if block_given? + calculate(:sum, column_name) end - # This calculates aggregate values in the given column. Methods for count, sum, average, - # minimum, and maximum have been added as shortcuts. + # This calculates aggregate values in the given column. Methods for #count, #sum, #average, + # #minimum, and #maximum have been added as shortcuts. # - # There are two basic forms of output: + # Person.calculate(:count, :all) # The same as Person.count + # Person.average(:age) # SELECT AVG(age) FROM people... # - # * 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. + # # Selects the minimum age for any family without any minors + # Person.group(:last_name).having("min(age) > 17").minimum(:age) # - # * Grouped values: This returns an ordered hash of the values and groups them. It - # takes either a column name, or the name of a belongs_to association. + # Person.sum("2 * age") # - # values = Person.group('last_name').maximum(:age) - # puts values["Drake"] - # # => 43 + # There are two basic forms of output: # - # drake = Family.find_by(last_name: 'Drake') - # values = Person.group(:family).maximum(:age) # Person belongs_to :family - # puts values[drake] - # # => 43 + # * 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. # - # values.each do |family, max_age| - # ... - # end + # * Grouped values: This returns an ordered hash of the values and groups them. It + # takes either a column name, or the name of a belongs_to association. # - # Person.calculate(:count, :all) # The same as Person.count - # Person.average(:age) # SELECT AVG(age) FROM people... + # values = Person.group('last_name').maximum(:age) + # puts values["Drake"] + # # => 43 # - # # Selects the minimum age for any family without any minors - # Person.group(:last_name).having("min(age) > 17").minimum(:age) + # drake = Family.find_by(last_name: 'Drake') + # values = Person.group(:family).maximum(:age) # Person belongs_to :family + # puts values[drake] + # # => 43 # - # Person.sum("2 * age") + # values.each do |family, max_age| + # ... + # end def calculate(operation, column_name) if column_name.is_a?(Symbol) && attribute_alias?(column_name) column_name = attribute_alias(column_name) @@ -118,7 +119,7 @@ module ActiveRecord end end - # Use <tt>pluck</tt> as a shortcut to select one or more attributes without + # Use #pluck as a shortcut to select one or more attributes without # loading a bunch of records just to grab the attributes you want. # # Person.pluck(:name) @@ -127,7 +128,7 @@ module ActiveRecord # # Person.all.map(&:name) # - # Pluck returns an <tt>Array</tt> of attribute values type-casted to match + # Pluck returns an Array of attribute values type-casted to match # the plucked column names, if they can be deduced. Plucking an SQL fragment # returns String values by default. # @@ -139,7 +140,7 @@ module ActiveRecord # # SELECT people.id, people.name FROM people # # => [[1, 'David'], [2, 'Jeremy'], [3, 'Jose']] # - # Person.uniq.pluck(:role) + # Person.distinct.pluck(:role) # # SELECT DISTINCT role FROM people # # => ['admin', 'member', 'guest'] # @@ -151,7 +152,7 @@ module ActiveRecord # # SELECT DATEDIFF(updated_at, created_at) FROM people # # => ['0', '27761', '173'] # - # See also +ids+. + # See also #ids. # def pluck(*column_names) column_names.map! do |column_name| @@ -195,7 +196,8 @@ module ActiveRecord def perform_calculation(operation, column_name) operation = operation.to_s.downcase - # If #count is used with #distinct / #uniq it is considered distinct. (eg. relation.distinct.count) + # If #count is used with #distinct (i.e. `relation.distinct.count`) it is + # considered distinct. distinct = self.distinct_value if operation == "count" @@ -297,7 +299,7 @@ module ActiveRecord ] select_values += select_values unless having_clause.empty? - select_values.concat group_fields.zip(group_aliases).map { |field,aliaz| + select_values.concat arel_columns(group_fields).zip(group_aliases).map { |field,aliaz| if field.respond_to?(:as) field.as(aliaz) else @@ -339,7 +341,6 @@ module ActiveRecord # 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) if keys.respond_to? :name keys = "#{keys.relation.name}.#{keys.name}" |