activerecord/lib/active_record/relation/calculations.rb
# frozen_string_literal: true
require "active_support/core_ext/enumerable"
module ActiveRecord
# = Active Record \Calculations
module Calculations
class ColumnAliasTracker # :nodoc:
def initialize(connection)
@connection = connection
@aliases = Hash.new(0)
end
def alias_for(field)
aliased_name = column_alias_for(field)
if @aliases[aliased_name] == 0
@aliases[aliased_name] = 1
aliased_name
else
# Update the count
count = @aliases[aliased_name] += 1
"#{truncate(aliased_name)}_#{count}"
end
end
private
# 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 truncate(name)
name.slice(0, @connection.table_alias_length - 2)
end
end
# 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", "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.
#
# When given a block, loads all records in the relation, if the relation
# hasn't been loaded yet. Calls the block with each record in the relation.
# Returns the number of records for which the block returns a truthy value.
#
# Person.count { |person| person.age > 21 }
# # => counts the number of people older that 21
#
# Note: If there are a lot of records in the relation, loading all records
# could result in performance issues.
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
# Same as #count, but performs the query asynchronously and returns an
# ActiveRecord::Promise.
def async_count(column_name = nil)
async.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.
#
# Person.average(:age) # => 35.8
def average(column_name)
calculate(:average, column_name)
end
# Same as #average, but performs the query asynchronously and returns an
# ActiveRecord::Promise.
def async_average(column_name)
async.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
# Same as #minimum, but performs the query asynchronously and returns an
# ActiveRecord::Promise.
def async_minimum(column_name)
async.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
# Same as #maximum, but performs the query asynchronously and returns an
# ActiveRecord::Promise.
def async_maximum(column_name)
async.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
#
# When given a block, loads all records in the relation, if the relation
# hasn't been loaded yet. Calls the block with each record in the relation.
# Returns the sum of +initial_value_or_column+ and the block return
# values:
#
# Person.sum { |person| person.age } # => 4562
# Person.sum(1000) { |person| person.age } # => 5562
#
# Note: If there are a lot of records in the relation, loading all records
# could result in performance issues.
def sum(initial_value_or_column = 0, &block)
if block_given?
map(&block).sum(initial_value_or_column)
else
calculate(:sum, initial_value_or_column)
end
end
# Same as #sum, but performs the query asynchronously and returns an
# ActiveRecord::Promise.
def async_sum(identity_or_column = nil)
async.sum(identity_or_column)
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)
operation = operation.to_s.downcase
if @none
case operation
when "count", "sum"
result = group_values.any? ? Hash.new : 0
return @async ? Promise::Complete.new(result) : result
when "average", "minimum", "maximum"
result = group_values.any? ? Hash.new : nil
return @async ? Promise::Complete.new(result) : result
end
end
if has_include?(column_name)
relation = apply_join_dependency
if operation == "count"
unless distinct_value || distinct_select?(column_name || select_for_count)
relation.distinct!
relation.select_values = Array(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
# Use #pluck as a shortcut to select one or more attributes without
# loading an entire record object per row.
#
# 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]
#
# Comment.joins(:person).pluck(:id, person: [:id])
# # SELECT comments.id, people.id FROM comments INNER JOIN people on comments.person_id = people.id
# # => [[1, 2], [2, 2]]
#
# 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 @none
if @async
return Promise::Complete.new([])
else
return []
end
end
if loaded? && all_attributes?(column_names)
result = records.pluck(*column_names)
if @async
return Promise::Complete.new(result)
else
return result
end
end
if has_include?(column_names.first)
relation = apply_join_dependency
relation.pluck(*column_names)
else
klass.disallow_raw_sql!(flattened_args(column_names))
columns = arel_columns(column_names)
relation = spawn
relation.select_values = columns
result = skip_query_cache_if_necessary do
if where_clause.contradiction?
ActiveRecord::Result.empty(async: @async)
else
klass.with_connection do |c|
c.select_all(relation.arel, "#{klass.name} Pluck", async: @async)
end
end
end
result.then do |result|
type_cast_pluck_values(result, columns)
end
end
end
# Same as #pluck, but performs the query asynchronously and returns an
# ActiveRecord::Promise.
def async_pluck(*column_names)
async.pluck(*column_names)
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)
result = records.pick(*column_names)
return @async ? Promise::Complete.new(result) : result
end
limit(1).pluck(*column_names).then(&:first)
end
# Same as #pick, but performs the query asynchronously and returns an
# ActiveRecord::Promise.
def async_pick(*column_names)
async.pick(*column_names)
end
# Returns the base model's ID's for the relation using the table's primary key
#
# Person.ids # SELECT people.id FROM people
# Person.joins(:company).ids # SELECT people.id FROM people INNER JOIN companies ON companies.id = people.company_id
def ids
primary_key_array = Array(primary_key)
if loaded?
result = records.map do |record|
if primary_key_array.one?
record._read_attribute(primary_key_array.first)
else
primary_key_array.map { |column| record._read_attribute(column) }
end
end
return @async ? Promise::Complete.new(result) : result
end
if has_include?(primary_key)
relation = apply_join_dependency.group(*primary_key_array)
return relation.ids
end
columns = arel_columns(primary_key_array)
relation = spawn
relation.select_values = columns
result = if relation.where_clause.contradiction?
ActiveRecord::Result.empty
else
skip_query_cache_if_necessary do
klass.with_connection do |c|
c.select_all(relation, "#{klass.name} Ids", async: @async)
end
end
end
result.then { |result| type_cast_pluck_values(result, columns) }
end
# Same as #ids, but performs the query asynchronously and returns an
# ActiveRecord::Promise.
def async_ids
async.ids
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|
column_name == :all ? Arel.sql("*", retryable: true) : Arel.sql(name)
end
end
def operation_over_aggregate_column(column, operation, distinct)
operation == "count" ? column.count(distinct) : column.public_send(operation)
end
def execute_simple_calculation(operation, column_name, distinct) # :nodoc:
if build_count_subquery?(operation, column_name, distinct)
# Shortcut when limit is zero.
return 0 if limit_value == 0
relation = self
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)
column = aggregate_column(column_name)
select_value = operation_over_aggregate_column(column, operation, distinct)
select_value.distinct = true if operation == "sum" && distinct
relation.select_values = [select_value]
query_builder = relation.arel
end
query_result = if relation.where_clause.contradiction?
ActiveRecord::Result.empty
else
skip_query_cache_if_necessary do
@klass.with_connection do |c|
c.select_all(query_builder, "#{@klass.name} #{operation.capitalize}", async: @async)
end
end
end
query_result.then do |result|
if operation != "count"
type = column.try(:type_caster) ||
lookup_cast_type_from_join_dependencies(column_name.to_s) || Type.default_value
type = type.subtype if Enum::EnumType === type
end
type_cast_calculated_value(result.cast_values.first, operation, type)
end
end
def execute_grouped_calculation(operation, column_name, distinct) # :nodoc:
group_fields = group_values
group_fields = group_fields.uniq if group_fields.size > 1
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)
@klass.with_connection do |connection|
column_alias_tracker = ColumnAliasTracker.new(connection)
group_aliases = group_fields.map { |field|
field = connection.visitor.compile(field) if Arel.arel_node?(field)
column_alias_tracker.alias_for(field.to_s.downcase)
}
group_columns = group_aliases.zip(group_fields)
column = aggregate_column(column_name)
column_alias = column_alias_tracker.alias_for("#{operation} #{column_name.to_s.downcase}")
select_value = operation_over_aggregate_column(column, operation, distinct)
select_value.as(adapter_class.quote_column_name(column_alias))
select_values = [select_value]
select_values += self.select_values unless having_clause.empty?
select_values.concat group_columns.map { |aliaz, field|
aliaz = adapter_class.quote_column_name(aliaz)
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
result = skip_query_cache_if_necessary do
connection.select_all(relation.arel, "#{@klass.name} #{operation.capitalize}", async: @async)
end
result.then do |calculated_data|
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] = col_name.try(:type_caster) ||
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 |(col_name, hash), i|
hash[col_name] = row[i]
end
end
if operation != "count"
type = column.try(:type_caster) ||
lookup_cast_type_from_join_dependencies(column_name.to_s) || Type.default_value
type = type.subtype if Enum::EnumType === type
end
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, type)
end
end
end
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 lookup_cast_type_from_join_dependencies(name, join_dependencies = build_join_dependencies)
each_join_dependencies(join_dependencies) do |join|
type = join.base_klass.attribute_types.fetch(name, nil)
return type if type
end
nil
end
def type_cast_pluck_values(result, columns)
cast_types = if result.columns.size != columns.size
klass.attribute_types
else
join_dependencies = nil
columns.map.with_index do |column, i|
column.try(:type_caster) ||
klass.attribute_types.fetch(name = result.columns[i]) do
join_dependencies ||= build_join_dependencies
lookup_cast_type_from_join_dependencies(name, join_dependencies) ||
result.column_types[name] || Type.default_value
end
end
end
result.cast_values(cast_types)
end
def type_cast_calculated_value(value, operation, type)
case operation
when "count"
value.to_i
when "sum"
type.deserialize(value || 0)
when "average"
case type.type
when :integer, :decimal
value&.to_d
else
type.deserialize(value)
end
else # "minimum", "maximum"
type.deserialize(value)
end
end
def select_for_count
if select_values.present?
return select_values.first if select_values.one?
select_values.map do |field|
column = arel_column(field.to_s) do |attr_name|
Arel.sql(attr_name)
end
if column.is_a?(Arel::Nodes::SqlLiteral)
column
else
"#{adapter_class.quote_table_name(column.relation.name)}.#{adapter_class.quote_column_name(column.name)}"
end
end.join(", ")
else
:all
end
end
def build_count_subquery?(operation, column_name, distinct)
# SQLite and older MySQL does not support `COUNT DISTINCT` with `*` or
# multiple columns, so we need to use subquery for this.
operation == "count" &&
(((column_name == :all || select_values.many?) && distinct) || has_limit_or_offset?)
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", retryable: true)
select_value = operation_over_aggregate_column(column_alias, "count", false)
relation.build_subquery(subquery_alias, select_value)
end
end
end