/activerecord/lib/active_record/relation/calculations.rb
Ruby | 311 lines | 181 code | 46 blank | 84 comment | 45 complexity | 84df62038426d847280898b7bb6b1822 MD5 | raw file
- require 'active_support/core_ext/object/blank'
- require 'active_support/core_ext/object/try'
- 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.count(:age, distinct: true)
- # # => counts the number of different age values
- def count(column_name = nil, options = {})
- 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 = {})
- 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 = {})
- 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 = {})
- 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)
- if block_given?
- self.to_a.sum(*args) {|*block_args| yield(*block_args)}
- else
- calculate(:sum, *args)
- end
- 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
- #
- # Examples:
- # 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 = {})
- relation = with_default_scope
- if relation.equal?(self)
- if eager_loading? || (includes_values.present? && references_eager_loaded_tables?)
- construct_relation_for_association_calculations.calculate(operation, column_name, options)
- else
- perform_calculation(operation, column_name, options)
- end
- else
- relation.calculate(operation, column_name, options)
- end
- rescue ThrowResult
- 0
- end
- # This method is designed to perform select by a single column as direct SQL query
- # Returns <tt>Array</tt> with values of the specified column name
- # The values has same data type as column.
- #
- # Examples:
- #
- # Person.pluck(:id) # SELECT people.id FROM people
- # Person.uniq.pluck(:role) # SELECT DISTINCT role FROM people
- # Person.where(:age => 21).limit(5).pluck(:id) # SELECT people.id FROM people WHERE people.age = 21 LIMIT 5
- #
- def pluck(column_name)
- key = column_name.to_s.split('.', 2).last
- if column_name.is_a?(Symbol) && column_names.include?(column_name.to_s)
- column_name = "#{table_name}.#{column_name}"
- end
- result = klass.connection.select_all(select(column_name).arel, nil, bind_values)
- types = result.column_types.merge klass.column_types
- column = types[key]
- result.map do |attributes|
- value = klass.initialize_attributes(attributes)[key]
- if column
- column.type_cast value
- else
- value
- end
- end
- end
- private
- def perform_calculation(operation, column_name, options = {})
- operation = operation.to_s.downcase
- distinct = options[:distinct]
- if operation == "count"
- column_name ||= (select_for_count || :all)
- 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)
- 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)
- relation.select_values = [select_value]
- query_builder = relation.arel
- end
- result = @klass.connection.select_value(query_builder, nil, relation.bind_values)
- type_cast_calculated_value(result, column_for(column_name), operation)
- end
- def execute_grouped_calculation(operation, column_name, distinct) #:nodoc:
- group_attr = group_values
- association = @klass.reflect_on_association(group_attr.first.to_sym)
- associated = group_attr.size == 1 && association && association.macro == :belongs_to # only count belongs_to associations
- group_fields = Array(associated ? association.foreign_key : group_attr)
- group_aliases = group_fields.map { |field| column_alias_for(field) }
- group_columns = group_aliases.zip(group_fields).map { |aliaz,field|
- [aliaz, column_for(field)]
- }
- group = @klass.connection.adapter_name == 'FrontBase' ? group_aliases : group_fields
- if operation == 'count' && column_name == :all
- aggregate_alias = 'count_all'
- else
- aggregate_alias = column_alias_for(operation, column_name)
- 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|
- "#{field} AS #{aliaz}"
- }
- relation = except(:group).group(group.join(','))
- 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, column|
- type_cast_calculated_value(row[aliaz], column)
- }
- key = key.first if key.size == 1
- key = key_records[key] if associated
- [key, type_cast_calculated_value(row[aggregate_alias], column_for(column_name), 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)
- table_name = keys.join(' ')
- table_name.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.to_s.split('.').last
- @klass.columns.detect { |c| c.name.to_s == 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
- def select_for_count
- if select_values.present?
- select = select_values.join(", ")
- select if select !~ /[,*]/
- 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