diff options
Diffstat (limited to 'activerecord/lib/active_record/associations/preloader.rb')
-rw-r--r-- | activerecord/lib/active_record/associations/preloader.rb | 119 |
1 files changed, 77 insertions, 42 deletions
diff --git a/activerecord/lib/active_record/associations/preloader.rb b/activerecord/lib/active_record/associations/preloader.rb index 82bf426b22..e49fc5d5c4 100644 --- a/activerecord/lib/active_record/associations/preloader.rb +++ b/activerecord/lib/active_record/associations/preloader.rb @@ -42,12 +42,9 @@ module ActiveRecord autoload :HasManyThrough, 'active_record/associations/preloader/has_many_through' autoload :HasOne, 'active_record/associations/preloader/has_one' autoload :HasOneThrough, 'active_record/associations/preloader/has_one_through' - autoload :HasAndBelongsToMany, 'active_record/associations/preloader/has_and_belongs_to_many' autoload :BelongsTo, 'active_record/associations/preloader/belongs_to' end - attr_reader :records, :associations, :preload_scope, :model - # Eager loads the named associations for the given Active Record record(s). # # In this description, 'association name' shall refer to the name passed @@ -82,38 +79,47 @@ module ActiveRecord # [ :books, :author ] # { author: :avatar } # [ :books, { author: :avatar } ] - def initialize(records, associations, preload_scope = nil) - @records = Array.wrap(records).compact.uniq - @associations = Array.wrap(associations) - @preload_scope = preload_scope || Relation.new(nil, nil) - end - def run - unless records.empty? - associations.each { |association| preload(association) } + NULL_RELATION = Struct.new(:values, :bind_values).new({}, []) + + def preload(records, associations, preload_scope = nil) + records = Array.wrap(records).compact.uniq + associations = Array.wrap(associations) + preload_scope = preload_scope || NULL_RELATION + + if records.empty? + [] + else + associations.flat_map { |association| + preloaders_on association, records, preload_scope + } end end private - def preload(association) + def preloaders_on(association, records, scope) case association when Hash - preload_hash(association) + preloaders_for_hash(association, records, scope) when Symbol - preload_one(association) + preloaders_for_one(association, records, scope) when String - preload_one(association.to_sym) + preloaders_for_one(association.to_sym, records, scope) else raise ArgumentError, "#{association.inspect} was not recognised for preload" end end - def preload_hash(association) - association.each do |parent, child| - Preloader.new(records, parent, preload_scope).run - Preloader.new(records.map { |record| record.send(parent) }.flatten, child).run - end + def preloaders_for_hash(association, records, scope) + parent, child = association.to_a.first # hash should only be of length 1 + + loaders = preloaders_for_one parent, records, scope + + recs = loaders.flat_map(&:preloaded_records).uniq + loaders.concat Array.wrap(child).flat_map { |assoc| + preloaders_on assoc, recs, scope + } end # Not all records have the same class, so group then preload group on the reflection @@ -123,52 +129,81 @@ module ActiveRecord # Additionally, polymorphic belongs_to associations can have multiple associated # classes, depending on the polymorphic_type field. So we group by the classes as # well. - def preload_one(association) - grouped_records(association).each do |reflection, klasses| - klasses.each do |klass, records| - preloader_for(reflection).new(klass, records, reflection, preload_scope).run + def preloaders_for_one(association, records, scope) + grouped_records(association, records).flat_map do |reflection, klasses| + klasses.map do |rhs_klass, rs| + loader = preloader_for(reflection, rs, rhs_klass).new(rhs_klass, rs, reflection, scope) + loader.run self + loader end end end - def grouped_records(association) - Hash[ - records_by_reflection(association).map do |reflection, records| - [reflection, records.group_by { |record| association_klass(reflection, record) }] - end - ] + def grouped_records(association, records) + reflection_records = records_by_reflection(association, records) + + reflection_records.each_with_object({}) do |(reflection, r_records),h| + h[reflection] = r_records.group_by { |record| + association_klass(reflection, record) + } + end end - def records_by_reflection(association) + def records_by_reflection(association, records) records.group_by do |record| - reflection = record.class.reflections[association] + reflection = record.class.reflect_on_association(association) - unless reflection - raise ActiveRecord::ConfigurationError, "Association named '#{association}' was not found; " \ - "perhaps you misspelled it?" - end - - reflection + reflection || raise_config_error(record, association) end end + def raise_config_error(record, association) + raise ActiveRecord::ConfigurationError, + "Association named '#{association}' was not found on #{record.class.name}; " \ + "perhaps you misspelled it?" + end + def association_klass(reflection, record) if reflection.macro == :belongs_to && reflection.options[:polymorphic] - klass = record.send(reflection.foreign_type) + klass = record.read_attribute(reflection.foreign_type.to_s) klass && klass.constantize else reflection.klass end end - def preloader_for(reflection) + class AlreadyLoaded + attr_reader :owners, :reflection + + def initialize(klass, owners, reflection, preload_scope) + @owners = owners + @reflection = reflection + end + + def run(preloader); end + + def preloaded_records + owners.flat_map { |owner| owner.association(reflection.name).target } + end + end + + class NullPreloader + def self.new(klass, owners, reflection, preload_scope); self; end + def self.run(preloader); end + end + + def preloader_for(reflection, owners, rhs_klass) + return NullPreloader unless rhs_klass + + if owners.first.association(reflection.name).loaded? + return AlreadyLoaded + end + case reflection.macro when :has_many reflection.options[:through] ? HasManyThrough : HasMany when :has_one reflection.options[:through] ? HasOneThrough : HasOne - when :has_and_belongs_to_many - HasAndBelongsToMany when :belongs_to BelongsTo end |