/activerecord/lib/active_record/relation/calculations.rb
Ruby | 384 lines | 201 code | 49 blank | 134 comment | 45 complexity | 5357ea32764bb4f60ea5dff7ac3c39cd MD5 | raw file
- 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 }
- #
- # If +count+ is used with +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 +select+, it will count the selected columns:
- #
- # Person.select(:age).count
- # # => counts the number of different age values
- #
- # Note: not all valid +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)
- calculate(: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
- # 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(*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)
- 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)
- else
- perform_calculation(operation, column_name)
- 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, bound_attributes)
- result.cast_values(klass.attribute_types)
- 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 && column_name != :all)
- end
- def perform_calculation(operation, column_name)
- 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 = unscope(:order)
- 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
- column_alias ||= @klass.connection.column_name_for_operation(operation, select_value)
- relation.select_values = [select_value]
- query_builder = relation.arel
- end
- result = @klass.connection.select_all(query_builder, nil, bound_attributes)
- row = result.first
- value = row && row.values.first
- column = result.column_types.fetch(column_alias) do
- type_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)
- associated = group_attrs.size == 1 && association && association.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_clause.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, relation.bound_attributes)
- 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 = 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
- type_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) { type_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 type_for(field)
- field_name = field.respond_to?(:name) ? field.name.to_s : field.to_s.split('.').last
- @klass.type_for_attribute(field_name)
- end
- def type_cast_calculated_value(value, type, operation = nil)
- case operation
- when 'count' then value.to_i
- when 'sum' then type.deserialize(value || 0)
- when 'average' then value.respond_to?(:to_d) ? value.to_d : value
- else type.deserialize(value)
- end
- 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