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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 +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 }
def count(column_name = nil, options = {})
# TODO: Remove options argument as soon we remove support to
# activerecord-deprecated_finders.
column_name, options = nil, column_name if column_name.is_a?(Hash)
calculate(:count, column_name, options)
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, options = {})
# TODO: Remove options argument as soon we remove support to
# activerecord-deprecated_finders.
calculate(:average, column_name, options)
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, options = {})
# TODO: Remove options argument as soon we remove support to
# activerecord-deprecated_finders.
calculate(:minimum, column_name, options)
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, options = {})
# TODO: Remove options argument as soon we remove support to
# activerecord-deprecated_finders.
calculate(:maximum, column_name, options)
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(*args)
calculate(:sum, *args)
end
# 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:
#
# * 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.
#
# * 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
#
# 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")
def calculate(operation, column_name, options = {})
# TODO: Remove options argument as soon we remove support to
# activerecord-deprecated_finders.
if column_name.is_a?(Symbol) && attribute_alias?(column_name)
column_name = attribute_alias(column_name)
end
if has_include?(column_name)
construct_relation_for_association_calculations.calculate(operation, column_name, options)
else
perform_calculation(operation, column_name, options)
end
end
# Use <tt>pluck</tt> 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 <tt>Array</tt> 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(:id)
# # SELECT people.id FROM people
# # => [1, 2, 3]
#
# Person.pluck(:id, :name)
# # SELECT people.id, people.name FROM people
# # => [[1, 'David'], [2, 'Jeremy'], [3, 'Jose']]
#
# Person.pluck('DISTINCT 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('DATEDIFF(updated_at, created_at)')
# # SELECT DATEDIFF(updated_at, created_at) FROM people
# # => ['0', '27761', '173']
#
def pluck(*column_names)
column_names.map! do |column_name|
if column_name.is_a?(Symbol) && attribute_alias?(column_name)
attribute_alias(column_name)
else
column_name.to_s
end
end
if has_include?(column_names.first)
construct_relation_for_association_calculations.pluck(*column_names)
else
relation = spawn
relation.select_values = column_names.map { |cn|
columns_hash.key?(cn) ? arel_table[cn] : cn
}
result = klass.connection.select_all(relation.arel, nil, bind_values)
columns = result.columns.map do |key|
klass.column_types.fetch(key) {
result.column_types.fetch(key) { result.identity_type }
}
end
result = result.map do |attributes|
values = klass.initialize_attributes(attributes).values
columns.zip(values).map { |column, value| column.type_cast value }
end
columns.one? ? result.map!(&:first) : result
end
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 has_include?(column_name)
eager_loading? || (includes_values.present? && (column_name || references_eager_loaded_tables?))
end
def perform_calculation(operation, column_name, options = {})
# TODO: Remove options argument as soon we remove support to
# activerecord-deprecated_finders.
operation = operation.to_s.downcase
# If #count is used with #distinct / #uniq it is considered distinct. (eg. relation.distinct.count)
distinct = self.distinct_value
if operation == "count"
column_name ||= select_for_count
unless arel.ast.grep(Arel::Nodes::OuterJoin).empty?
distinct = true
end
column_name = primary_key if column_name == :all && distinct
distinct = nil if column_name =~ /\s*DISTINCT[\s(]+/i
end
if group_values.any?
execute_grouped_calculation(operation, column_name, distinct)
else
execute_simple_calculation(operation, column_name, distinct)
end
end
def aggregate_column(column_name)
if @klass.column_names.include?(column_name.to_s)
Arel::Attribute.new(@klass.unscoped.table, column_name)
else
Arel.sql(column_name == :all ? "*" : column_name.to_s)
end
end
def operation_over_aggregate_column(column, operation, distinct)
operation == 'count' ? column.count(distinct) : column.send(operation)
end
def execute_simple_calculation(operation, column_name, distinct) #:nodoc:
# Postgresql doesn't like ORDER BY when there are no GROUP BY
relation = reorder(nil)
column_alias = column_name
if operation == "count" && (relation.limit_value || relation.offset_value)
# Shortcut when limit is zero.
return 0 if relation.limit_value == 0
query_builder = build_count_subquery(relation, column_name, distinct)
else
column = aggregate_column(column_name)
select_value = operation_over_aggregate_column(column, operation, distinct)
column_alias = select_value.alias
relation.select_values = [select_value]
query_builder = relation.arel
end
result = @klass.connection.select_all(query_builder, nil, relation.bind_values)
row = result.first
value = row && row.values.first
column = result.column_types.fetch(column_alias) do
column_for(column_name)
end
type_cast_calculated_value(value, column, operation)
end
def execute_grouped_calculation(operation, column_name, distinct) #:nodoc:
group_attrs = group_values
if group_attrs.first.respond_to?(:to_sym)
association = @klass.reflect_on_association(group_attrs.first.to_sym)
associated = group_attrs.size == 1 && association && association.macro == :belongs_to # only count belongs_to associations
group_fields = Array(associated ? association.foreign_key : group_attrs)
else
group_fields = group_attrs
end
group_aliases = group_fields.map { |field|
column_alias_for(field)
}
group_columns = group_aliases.zip(group_fields).map { |aliaz,field|
[aliaz, field]
}
group = group_fields
if operation == 'count' && column_name == :all
aggregate_alias = 'count_all'
else
aggregate_alias = column_alias_for([operation, column_name].join(' '))
end
select_values = [
operation_over_aggregate_column(
aggregate_column(column_name),
operation,
distinct).as(aggregate_alias)
]
select_values += select_values unless having_values.empty?
select_values.concat group_fields.zip(group_aliases).map { |field,aliaz|
if field.respond_to?(:as)
field.as(aliaz)
else
"#{field} AS #{aliaz}"
end
}
relation = except(:group)
relation.group_values = group
relation.select_values = select_values
calculated_data = @klass.connection.select_all(relation, nil, bind_values)
if association
key_ids = calculated_data.collect { |row| row[group_aliases.first] }
key_records = association.klass.base_class.find(key_ids)
key_records = Hash[key_records.map { |r| [r.id, r] }]
end
Hash[calculated_data.map do |row|
key = group_columns.map { |aliaz, col_name|
column = calculated_data.column_types.fetch(aliaz) do
column_for(col_name)
end
type_cast_calculated_value(row[aliaz], column)
}
key = key.first if key.size == 1
key = key_records[key] if associated
column_type = calculated_data.column_types.fetch(aggregate_alias) { column_for(column_name) }
[key, type_cast_calculated_value(row[aggregate_alias], column_type, operation)]
end]
end
# Converts the given keys 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"
# column_alias_for("count", "id") # => "count_id"
def column_alias_for(keys)
if keys.respond_to? :name
keys = "#{keys.relation.name}.#{keys.name}"
end
table_name = keys.to_s.downcase
table_name.gsub!(/\*/, 'all')
table_name.gsub!(/\W+/, ' ')
table_name.strip!
table_name.gsub!(/ +/, '_')
@klass.connection.table_alias_for(table_name)
end
def column_for(field)
field_name = field.respond_to?(:name) ? field.name.to_s : field.to_s.split('.').last
@klass.columns_hash[field_name]
end
def type_cast_calculated_value(value, column, operation = nil)
case operation
when 'count' then value.to_i
when 'sum' then type_cast_using_column(value || 0, column)
when 'average' then value.respond_to?(:to_d) ? value.to_d : value
else type_cast_using_column(value, column)
end
end
def type_cast_using_column(value, column)
column ? column.type_cast(value) : value
end
# TODO: refactor to allow non-string `select_values` (eg. Arel nodes).
def select_for_count
if select_values.present?
select_values.join(", ")
else
:all
end
end
def build_count_subquery(relation, column_name, distinct)
column_alias = Arel.sql('count_column')
subquery_alias = Arel.sql('subquery_for_count')
aliased_column = aggregate_column(column_name == :all ? 1 : column_name).as(column_alias)
relation.select_values = [aliased_column]
subquery = relation.arel.as(subquery_alias)
sm = Arel::SelectManager.new relation.engine
select_value = operation_over_aggregate_column(column_alias, 'count', distinct)
sm.project(select_value).from(subquery)
end
end
end
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