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 # Use pluck as a shortcut to select a single attribute without # loading a bunch of records just to grab one attribute 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 name, if it can be deduced. Plucking a SQL fragment # returns String values by default. # # Examples: # # Person.pluck(:id) # # SELECT people.id FROM people # # => [1, 2, 3] # # Person.uniq.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('DATEDIFF(updated_at, created_at)') # # SELECT DATEDIFF(updated_at, created_at) FROM people # # => ['0', '27761', '173'] # def pluck(column_name) 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) key = result.columns.first column = klass.column_types.fetch(key) { result.column_types.fetch(key) { Class.new { def type_cast(v); v; end }.new } } result.map do |attributes| raise ArgumentError, "Pluck expects to select just one attribute: #{attributes.inspect}" unless attributes.one? value = klass.initialize_attributes(attributes).values.first column.type_cast(value) end end # Pluck all the ID's for the relation using the table's primary key # # Examples: # # 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 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