/activerecord/lib/active_record/relation/calculations.rb
Ruby | 450 lines | 244 code | 54 blank | 152 comment | 62 complexity | e621d3b0221857d20dca3213f62e6608 MD5 | raw file
- # frozen_string_literal: true
- require "active_support/core_ext/enumerable"
- module ActiveRecord
- module Calculations
- # Count the records.
- #
- # Person.count
- # # => the total count of all people
- #
- # Person.count(:age)
- # # => returns the total count of all people whose age is present in database
- #
- # Person.count(:all)
- # # => performs a COUNT(*) (:all is an alias for '*')
- #
- # Person.distinct.count(:age)
- # # => counts the number of different age values
- #
- # 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 {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.
- #
- # Article.group(:status, :category).count
- # # => {["draft", "business"]=>10, ["draft", "technology"]=>4,
- # ["published", "business"]=>0, ["published", "technology"]=>2}
- #
- # 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 {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)
- if block_given?
- unless column_name.nil?
- raise ArgumentError, "Column name argument is not supported when a block is passed."
- end
- super()
- else
- calculate(:count, column_name)
- end
- end
- # Calculates the average value on a given column. Returns +nil+ if there's
- # no row. See #calculate for examples with options.
- #
- # Person.average(:age) # => 35.8
- def average(column_name)
- calculate(:average, column_name)
- 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)
- calculate(:minimum, column_name)
- 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)
- calculate(:maximum, column_name)
- 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 = nil)
- if block_given?
- unless column_name.nil?
- raise ArgumentError, "Column name argument is not supported when a block is passed."
- end
- super()
- else
- calculate(:sum, column_name)
- end
- end
- # 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
- 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 = []
- end
- relation.calculate(operation, column_name)
- else
- perform_calculation(operation, column_name)
- end
- end
- # 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)
- #
- # instead of
- #
- # Person.all.map(&:name)
- #
- # 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.
- #
- # Person.pluck(:name)
- # # SELECT people.name FROM people
- # # => ['David', 'Jeremy', 'Jose']
- #
- # Person.pluck(:id, :name)
- # # SELECT people.id, people.name FROM people
- # # => [[1, 'David'], [2, 'Jeremy'], [3, 'Jose']]
- #
- # Person.distinct.pluck(:role)
- # # SELECT DISTINCT role FROM people
- # # => ['admin', 'member', 'guest']
- #
- # Person.where(age: 21).limit(5).pluck(:id)
- # # SELECT people.id FROM people WHERE people.age = 21 LIMIT 5
- # # => [2, 3]
- #
- # Person.pluck(Arel.sql('DATEDIFF(updated_at, created_at)'))
- # # SELECT DATEDIFF(updated_at, created_at) FROM people
- # # => ['0', '27761', '173']
- #
- # See also #ids.
- #
- def pluck(*column_names)
- if loaded? && all_attributes?(column_names)
- return records.pluck(*column_names)
- end
- if has_include?(column_names.first)
- relation = apply_join_dependency
- relation.pluck(*column_names)
- else
- klass.disallow_raw_sql!(column_names)
- relation = spawn
- relation.select_values = column_names
- result = skip_query_cache_if_necessary do
- if where_clause.contradiction?
- ActiveRecord::Result.new([], [])
- else
- klass.connection.select_all(relation.arel, nil)
- end
- end
- result.cast_values(klass.attribute_types)
- end
- end
- # Pick the value(s) from the named column(s) in the current relation.
- # This is short-hand for <tt>relation.limit(1).pluck(*column_names).first</tt>, and is primarily useful
- # when you have a relation that's already narrowed down to a single row.
- #
- # Just like #pluck, #pick will only load the actual value, not the entire record object, so it's also
- # more efficient. The value is, again like with pluck, typecast by the column type.
- #
- # Person.where(id: 1).pick(:name)
- # # SELECT people.name FROM people WHERE id = 1 LIMIT 1
- # # => 'David'
- #
- # Person.where(id: 1).pick(:name, :email_address)
- # # SELECT people.name, people.email_address FROM people WHERE id = 1 LIMIT 1
- # # => [ 'David', 'david@loudthinking.com' ]
- def pick(*column_names)
- if loaded? && all_attributes?(column_names)
- return records.pick(*column_names)
- end
- limit(1).pluck(*column_names).first
- end
- # Pluck all the ID's for the relation using the table's primary key
- #
- # Person.ids # SELECT people.id FROM people
- # Person.joins(:companies).ids # SELECT people.id FROM people INNER JOIN companies ON companies.person_id = people.id
- def ids
- pluck primary_key
- end
- private
- def all_attributes?(column_names)
- (column_names.map(&:to_s) - @klass.attribute_names - @klass.attribute_aliases.keys).empty?
- end
- def has_include?(column_name)
- eager_loading? || (includes_values.present? && column_name && column_name != :all)
- end
- def perform_calculation(operation, column_name)
- operation = operation.to_s.downcase
- # If #count is used with #distinct (i.e. `relation.distinct.count`) it is
- # considered distinct.
- distinct = distinct_value
- if operation == "count"
- column_name ||= select_for_count
- if column_name == :all
- if !distinct
- distinct = distinct_select?(select_for_count) if group_values.empty?
- elsif group_values.any? || select_values.empty? && order_values.empty?
- column_name = primary_key
- end
- elsif distinct_select?(column_name)
- distinct = nil
- end
- end
- if group_values.any?
- execute_grouped_calculation(operation, column_name, distinct)
- else
- execute_simple_calculation(operation, column_name, distinct)
- end
- end
- def distinct_select?(column_name)
- column_name.is_a?(::String) && /\bDISTINCT[\s(]/i.match?(column_name)
- end
- def aggregate_column(column_name)
- return column_name if Arel::Expressions === column_name
- arel_column(column_name.to_s) do |name|
- Arel.sql(column_name == :all ? "*" : name)
- end
- end
- def operation_over_aggregate_column(column_name, operation, distinct)
- column = aggregate_column(column_name)
- operation == "count" ? column.count(distinct) : column.send(operation)
- end
- def execute_simple_calculation(operation, column_name, distinct) #:nodoc:
- if operation == "count" && (column_name == :all && distinct || has_limit_or_offset?)
- # Shortcut when limit is zero.
- return 0 if limit_value == 0
- query_builder = build_count_subquery(spawn, column_name, distinct)
- else
- # PostgreSQL doesn't like ORDER BY when there are no GROUP BY
- relation = unscope(:order).distinct!(false)
- select_value = operation_over_aggregate_column(column_name, operation, distinct)
- select_value.distinct = true if operation == "sum" && distinct
- relation.select_values = [select_value]
- query_builder = relation.arel
- end
- result = skip_query_cache_if_necessary { @klass.connection.select_all(query_builder) }
- type_cast_calculated_value(result.cast_values.first, operation) do |value|
- if value.is_a?(String) &&
- column = klass.columns_hash[column_name.to_s]
- type = connection.lookup_cast_type_from_column(column)
- type.deserialize(value)
- else
- value
- end
- end
- end
- def execute_grouped_calculation(operation, column_name, distinct) #:nodoc:
- group_fields = group_values
- if group_fields.size == 1 && group_fields.first.respond_to?(:to_sym)
- association = klass._reflect_on_association(group_fields.first)
- associated = association && association.belongs_to? # only count belongs_to associations
- group_fields = Array(association.foreign_key) if associated
- end
- group_fields = arel_columns(group_fields)
- group_aliases = group_fields.map { |field|
- field = connection.visitor.compile(field) if Arel.arel_node?(field)
- column_alias_for(field.to_s.downcase)
- }
- group_columns = group_aliases.zip(group_fields)
- column_alias = column_alias_for("#{operation} #{column_name.to_s.downcase}")
- select_value = operation_over_aggregate_column(column_name, operation, distinct)
- select_value.as(column_alias)
- select_values = [select_value]
- select_values += self.select_values unless having_clause.empty?
- select_values.concat group_columns.map { |aliaz, field|
- if field.respond_to?(:as)
- field.as(aliaz)
- else
- "#{field} AS #{aliaz}"
- end
- }
- relation = except(:group).distinct!(false)
- relation.group_values = group_fields
- relation.select_values = select_values
- calculated_data = skip_query_cache_if_necessary { @klass.connection.select_all(relation.arel, nil) }
- if association
- key_ids = calculated_data.collect { |row| row[group_aliases.first] }
- key_records = association.klass.base_class.where(association.klass.base_class.primary_key => key_ids)
- key_records = key_records.index_by(&:id)
- end
- key_types = group_columns.each_with_object({}) do |(aliaz, col_name), types|
- types[aliaz] = type_for(col_name) do
- calculated_data.column_types.fetch(aliaz, Type.default_value)
- end
- end
- hash_rows = calculated_data.cast_values(key_types).map! do |row|
- calculated_data.columns.each_with_object({}).with_index do |(column, hash), i|
- hash[column] = row[i]
- end
- end
- type = nil
- hash_rows.each_with_object({}) do |row, result|
- key = group_aliases.map { |aliaz| row[aliaz] }
- key = key.first if key.size == 1
- key = key_records[key] if associated
- result[key] = type_cast_calculated_value(row[column_alias], operation) do |value|
- if value.is_a?(String) &&
- (type || column = klass.columns_hash[column_name.to_s])
- type ||= connection.lookup_cast_type_from_column(column)
- type.deserialize(value)
- else
- value
- end
- end
- end
- end
- # Converts the given field 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"
- def column_alias_for(field)
- column_alias = +field
- column_alias.gsub!(/\*/, "all")
- column_alias.gsub!(/\W+/, " ")
- column_alias.strip!
- column_alias.gsub!(/ +/, "_")
- connection.table_alias_for(column_alias)
- end
- def type_for(field, &block)
- field_name = field.respond_to?(:name) ? field.name.to_s : field.to_s.split(".").last
- @klass.type_for_attribute(field_name, &block)
- end
- def type_cast_calculated_value(value, operation)
- case operation
- when "count", "sum"
- value || 0
- when "average"
- value&.respond_to?(:to_d) ? value.to_d : value
- else # "minimum", "maximum"
- yield value
- end
- end
- def select_for_count
- if select_values.present?
- return select_values.first if select_values.one?
- select_values.join(", ")
- else
- :all
- end
- end
- def build_count_subquery(relation, column_name, distinct)
- if column_name == :all
- column_alias = Arel.star
- relation.select_values = [ Arel.sql(FinderMethods::ONE_AS_ONE) ] unless distinct
- else
- column_alias = Arel.sql("count_column")
- relation.select_values = [ aggregate_column(column_name).as(column_alias) ]
- end
- subquery_alias = Arel.sql("subquery_for_count")
- select_value = operation_over_aggregate_column(column_alias, "count", false)
- relation.build_subquery(subquery_alias, select_value)
- end
- end
- end