instance method `calculate`

Ruby on Rails 6.0.6

Since v3.0.20

Available in: v3.0.20 v3.1.12 v3.2.22.5 v4.0.13 v4.1.16 v4.2.9 v5.2.8.1 v6.0.6 v6.1.7.10 v7.0.10 v7.1.6 v7.2.3 v8.0.4 v8.1.2

Compare with:

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

operation req
column_name req

Source

# File activerecord/lib/active_record/relation/calculations.rb, line 127
    def calculate(operation, column_name)
      if has_include?(column_name)
        relation = apply_join_dependency

        if operation.to_s.downcase == "count"
          unless distinct_value || distinct_select?(column_name || select_for_count)
            relation.distinct!
            relation.select_values = [ klass.primary_key || table[Arel.star] ]
          end
          # PostgreSQL: ORDER BY expressions must appear in SELECT list when using DISTINCT
          relation.order_values = [] if group_values.empty?
        end

        relation.calculate(operation, column_name)
      else
        perform_calculation(operation, column_name)
      end
    end

Defined in activerecord/lib/active_record/relation/calculations.rb line 127 · View on GitHub · Improve this page · Find usages on GitHub

Defined in ActiveRecord::Calculations

Signature

Parameters