instance method
calculate
Ruby on Rails 5.0.7.2
Since v3.0.20Signature
calculate(operation, column_name)This calculates aggregate values in the given column. Methods for #count, #sum, #average, #minimum, and #maximum have been added as shortcuts.
Person.calculate(:count, :all) # The same as Person.count
Person.average(:age) # SELECT AVG(age) FROM people...
# Selects the minimum age for any family without any minors
Person.group(:last_name).having("min(age) > 17").minimum(:age)
Person.sum("2 * age")
There are two basic forms of output:
-
Single aggregate value: The single value is type cast to Integer 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. It takes either a column name, or the name of a belongs_to association.
values = Person.group('last_name').maximum(:age) puts values["Drake"] # => 43 drake = Family.find_by(last_name: 'Drake') values = Person.group(:family).maximum(:age) # Person belongs_to :family puts values[drake] # => 43 values.each do |family, max_age| ... end
Parameters
-
operationreq -
column_namereq
Source
# File activerecord/lib/active_record/relation/calculations.rb, line 110
def calculate(operation, column_name)
if column_name.is_a?(Symbol) && attribute_alias?(column_name)
column_name = attribute_alias(column_name)
end
if has_include?(column_name)
relation = construct_relation_for_association_calculations
relation = relation.distinct if operation.to_s.downcase == "count"
relation.calculate(operation, column_name)
else
perform_calculation(operation, column_name)
end
end
Defined in activerecord/lib/active_record/relation/calculations.rb line 110
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Defined in ActiveRecord::Calculations