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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)
through_scope = through_scope()
preloader.preload(owners,
through_reflection.name,
through_scope)
through_records = owners.map do |owner|
center = owner.association(through_reflection.name).target
[owner, Array(center)]
end
reset_association(owners, through_reflection.name, through_scope)
middle_records = through_records.flat_map(&:last)
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
through_records.each_with_object({}) do |(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|
r.association(source_reflection.name).target
}.compact
# Respect the order on `reflection_scope` if it exists, else use the natural order.
if reflection_scope.values[:order].present?
@id_map ||= id_to_index_map @preloaded_records
rhs_records.sort_by { |rhs| @id_map[rhs] }
else
rhs_records
end
end
end
end
private
def id_to_index_map(ids)
id_map = {}
ids.each_with_index { |id, index| id_map[id] = index }
id_map
end
def reset_association(owners, association_name, through_scope)
should_reset = (through_scope != through_reflection.klass.unscoped) ||
(options[:source_type] && through_reflection.collection?)
# Don't 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_clause.empty?
scope.includes_values = Array(reflection_scope.values[:includes] || options[:source])
scope.where_clause = reflection_scope.where_clause
end
scope.references! reflection_scope.values[:references]
if scope.eager_loading? && order_values = reflection_scope.values[:order]
scope = scope.order(order_values)
end
end
scope
end
end
end
end
end
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