module ActiveRecord module Associations class Preloader class Association #:nodoc: attr_reader :owners, :reflection, :preload_scope, :model, :klass attr_reader :preloaded_records def initialize(klass, owners, reflection, preload_scope) @klass = klass @owners = owners @reflection = reflection @preload_scope = preload_scope @model = owners.first && owners.first.class @scope = nil @preloaded_records = [] end def run(preloader) preload(preloader) end def preload(preloader) raise NotImplementedError end def scope @scope ||= build_scope end def records_for(ids) query_scope(ids) end def query_scope(ids) scope.where(association_key_name => ids) end def table klass.arel_table end # The name of the key on the associated records def association_key_name raise NotImplementedError end # This is overridden by HABTM as the condition should be on the foreign_key column in # the join table def association_key klass.arel_attribute(association_key_name, table) end # The name of the key on the model which declares the association def owner_key_name raise NotImplementedError end def options reflection.options end private def associated_records_by_owner(preloader) records = load_records do |record| owner = owners_by_key[convert_key(record[association_key_name])] association = owner.association(reflection.name) association.set_inverse_instance(record) end owners.each_with_object({}) do |owner, result| result[owner] = records[convert_key(owner[owner_key_name])] || [] end end def owner_keys unless defined?(@owner_keys) @owner_keys = owners.map do |owner| owner[owner_key_name] end @owner_keys.uniq! @owner_keys.compact! end @owner_keys end def owners_by_key unless defined?(@owners_by_key) @owners_by_key = owners.each_with_object({}) do |owner, h| h[convert_key(owner[owner_key_name])] = owner end end @owners_by_key end def key_conversion_required? @key_conversion_required ||= association_key_type != owner_key_type end def convert_key(key) if key_conversion_required? key.to_s else key end end def association_key_type @klass.type_for_attribute(association_key_name.to_s).type end def owner_key_type @model.type_for_attribute(owner_key_name.to_s).type end def load_records(&block) return {} if owner_keys.empty? # Some databases impose a limit on the number of ids in a list (in Oracle it's 1000) # Make several smaller queries if necessary or make one query if the adapter supports it slices = owner_keys.each_slice(klass.connection.in_clause_length || owner_keys.size) @preloaded_records = slices.flat_map do |slice| records_for(slice).load(&block) end @preloaded_records.group_by do |record| convert_key(record[association_key_name]) end end def reflection_scope @reflection_scope ||= reflection.scope_for(klass) end def build_scope scope = klass.unscoped values = reflection_scope.values preload_values = preload_scope.values scope.where_clause = reflection_scope.where_clause + preload_scope.where_clause scope.references_values = Array(values[:references]) + Array(preload_values[:references]) if preload_values[:select] || values[:select] scope._select!(preload_values[:select] || values[:select]) end scope.includes! preload_values[:includes] || values[:includes] if preload_scope.joins_values.any? scope.joins!(preload_scope.joins_values) else scope.joins!(reflection_scope.joins_values) end if order_values = preload_values[:order] || values[:order] scope.order!(order_values) end if preload_values[:reordering] || values[:reordering] scope.reordering_value = true end if preload_values[:readonly] || values[:readonly] scope.readonly! end if options[:as] scope.where!(klass.table_name => { reflection.type => model.base_class.sti_name }) end scope.unscope_values = Array(values[:unscope]) + Array(preload_values[:unscope]) klass.default_scoped.merge(scope) end end end end end