module ActiveRecord module Associations class Preloader class Association #:nodoc: attr_reader :owners, :reflection, :preload_options, :model, :klass def initialize(klass, owners, reflection, preload_options) @klass = klass @owners = owners @reflection = reflection @preload_options = preload_options || {} @model = owners.first && owners.first.class @scoped = nil @owners_by_key = nil end def run unless owners.first.association(reflection.name).loaded? preload end end def preload raise NotImplementedError end def scoped @scoped ||= build_scope end def records_for(ids) scoped.where(association_key.in(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 table[association_key_name] end # The name of the key on the model which declares the association def owner_key_name raise NotImplementedError end # We're converting to a string here because postgres will return the aliased association # key in a habtm as a string (for whatever reason) def owners_by_key @owners_by_key ||= owners.group_by do |owner| key = owner[owner_key_name] key && key.to_s end end def options reflection.options end private def associated_records_by_owner owners_map = owners_by_key owner_keys = owners_map.keys.compact if klass.nil? || owner_keys.empty? records = [] else # 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 sliced = owner_keys.each_slice(model.connection.in_clause_length || owner_keys.size) records = sliced.map { |slice| records_for(slice) }.flatten end # Each record may have multiple owners, and vice-versa records_by_owner = Hash[owners.map { |owner| [owner, []] }] records.each do |record| owner_key = record[association_key_name].to_s owners_map[owner_key].each do |owner| records_by_owner[owner] << record end end records_by_owner end def build_scope scope = klass.scoped scope = scope.where(process_conditions(options[:conditions])) scope = scope.where(process_conditions(preload_options[:conditions])) scope = scope.select(preload_options[:select] || options[:select] || table[Arel.star]) scope = scope.includes(preload_options[:include] || options[:include]) if options[:as] scope = scope.where( klass.table_name => { reflection.type => model.base_class.sti_name } ) end scope end def process_conditions(conditions) if conditions.respond_to?(:to_proc) && !conditions.is_a?(Hash) conditions = klass.send(:instance_eval, &conditions) end conditions end end end end end