module ActiveRecord module Associations class Preloader module ThroughAssociation #:nodoc: def through_reflection reflection.through_reflection end def source_reflection reflection.source_reflection end def associated_records_by_owner(preloader) preloader.preload(owners, through_reflection.name, through_scope) through_records = owners.map do |owner| association = owner.association through_reflection.name [owner, Array(association.reader)] end reset_association owners, through_reflection.name middle_records = through_records.map { |(_,rec)| rec }.flatten preloaders = preloader.preload(middle_records, source_reflection.name, reflection_scope) @preloaded_records = preloaders.flat_map(&:preloaded_records) middle_to_pl = preloaders.each_with_object({}) do |pl,h| pl.owners.each { |middle| h[middle] = pl } end record_offset = {} @preloaded_records.each_with_index do |record,i| record_offset[record] = i end through_records.each_with_object({}) { |(lhs,center),records_by_owner| pl_to_middle = center.group_by { |record| middle_to_pl[record] } records_by_owner[lhs] = pl_to_middle.flat_map do |pl, middles| rhs_records = middles.flat_map { |r| association = r.association source_reflection.name association.reader }.compact rhs_records.sort_by { |rhs| record_offset[rhs] } end } end private def reset_association(owners, association_name) should_reset = (through_scope != through_reflection.klass.unscoped) || (reflection.options[:source_type] && through_reflection.collection?) # Dont cache the association - we would only be caching a subset if should_reset owners.each { |owner| owner.association(association_name).reset } end end def through_scope scope = through_reflection.klass.unscoped if options[:source_type] scope.where! reflection.foreign_type => options[:source_type] else unless reflection_scope.where_values.empty? scope.includes_values = Array(reflection_scope.values[:includes] || options[:source]) scope.where_values = reflection_scope.values[:where] end scope.references! reflection_scope.values[:references] scope.order! reflection_scope.values[:order] if scope.eager_loading? end scope end end end end end