module ActiveRecord
module AssociationPreload #:nodoc:
def self.included(base)
base.extend(ClassMethods)
end
module ClassMethods
# Loads the named associations for the activerecord record (or records) given
# preload_options is passed only one level deep: don't pass to the child associations when associations is a Hash
protected
def preload_associations(records, associations, preload_options={})
records = [records].flatten.compact.uniq
return if records.empty?
case associations
when Array then associations.each {|association| preload_associations(records, association, preload_options)}
when Symbol, String then preload_one_association(records, associations.to_sym, preload_options)
when Hash then
associations.each do |parent, child|
raise "parent must be an association name" unless parent.is_a?(String) || parent.is_a?(Symbol)
preload_associations(records, parent, preload_options)
reflection = reflections[parent]
parents = records.map {|record| record.send(reflection.name)}.flatten
unless parents.empty? || parents.first.nil?
parents.first.class.preload_associations(parents, child)
end
end
end
end
private
def preload_one_association(records, association, preload_options={})
class_to_reflection = {}
# Not all records have the same class, so group then preload
# group on the reflection itself so that if various subclass share the same association then we do not split them
# unnecessarily
records.group_by {|record| class_to_reflection[record.class] ||= record.class.reflections[association]}.each do |reflection, records|
raise ConfigurationError, "Association named '#{ association }' was not found; perhaps you misspelled it?" unless reflection
send("preload_#{reflection.macro}_association", records, reflection, preload_options)
end
end
def add_preloaded_records_to_collection(parent_records, reflection_name, associated_record)
parent_records.each do |parent_record|
association_proxy = parent_record.send(reflection_name)
association_proxy.loaded
association_proxy.target.push(*[associated_record].flatten)
end
end
def add_preloaded_record_to_collection(parent_records, reflection_name, associated_record)
parent_records.each do |parent_record|
parent_record.send("set_#{reflection_name}_target", associated_record)
end
end
def set_association_collection_records(id_to_record_map, reflection_name, associated_records, key)
associated_records.each do |associated_record|
mapped_records = id_to_record_map[associated_record[key].to_s]
add_preloaded_records_to_collection(mapped_records, reflection_name, associated_record)
end
end
def set_association_single_records(id_to_record_map, reflection_name, associated_records, key)
seen_keys = {}
associated_records.each do |associated_record|
#this is a has_one or belongs_to: there should only be one record.
#Unfortunately we can't (in portable way) ask the database for 'all records where foo_id in (x,y,z), but please
# only one row per distinct foo_id' so this where we enforce that
next if seen_keys[associated_record[key].to_s]
seen_keys[associated_record[key].to_s] = true
mapped_records = id_to_record_map[associated_record[key].to_s]
mapped_records.each do |mapped_record|
mapped_record.send("set_#{reflection_name}_target", associated_record)
end
end
end
def construct_id_map(records)
id_to_record_map = {}
ids = []
records.each do |record|
ids << record.id
mapped_records = (id_to_record_map[record.id.to_s] ||= [])
mapped_records << record
end
ids.uniq!
return id_to_record_map, ids
end
def preload_has_and_belongs_to_many_association(records, reflection, preload_options={})
table_name = reflection.klass.quoted_table_name
id_to_record_map, ids = construct_id_map(records)
records.each {|record| record.send(reflection.name).loaded}
options = reflection.options
conditions = "t0.#{reflection.primary_key_name} IN (?)"
conditions << append_conditions(options, preload_options)
associated_records = reflection.klass.find(:all, :conditions => [conditions, ids],
:include => options[:include],
:joins => "INNER JOIN #{connection.quote_table_name options[:join_table]} as t0 ON #{reflection.klass.quoted_table_name}.#{reflection.klass.primary_key} = t0.#{reflection.association_foreign_key}",
:select => "#{options[:select] || table_name+'.*'}, t0.#{reflection.primary_key_name} as the_parent_record_id",
:order => options[:order])
set_association_collection_records(id_to_record_map, reflection.name, associated_records, 'the_parent_record_id')
end
def preload_has_one_association(records, reflection, preload_options={})
id_to_record_map, ids = construct_id_map(records)
options = reflection.options
records.each {|record| record.send("set_#{reflection.name}_target", nil)}
if options[:through]
through_records = preload_through_records(records, reflection, options[:through])
through_reflection = reflections[options[:through]]
through_primary_key = through_reflection.primary_key_name
unless through_records.empty?
source = reflection.source_reflection.name
through_records.first.class.preload_associations(through_records, source)
through_records.each do |through_record|
add_preloaded_record_to_collection(id_to_record_map[through_record[through_primary_key].to_s],
reflection.name, through_record.send(source))
end
end
else
set_association_single_records(id_to_record_map, reflection.name, find_associated_records(ids, reflection, preload_options), reflection.primary_key_name)
end
end
def preload_has_many_association(records, reflection, preload_options={})
id_to_record_map, ids = construct_id_map(records)
records.each {|record| record.send(reflection.name).loaded}
options = reflection.options
if options[:through]
through_records = preload_through_records(records, reflection, options[:through])
through_reflection = reflections[options[:through]]
through_primary_key = through_reflection.primary_key_name
unless through_records.empty?
source = reflection.source_reflection.name
#add conditions from reflection!
through_records.first.class.preload_associations(through_records, source, reflection.options)
through_records.each do |through_record|
add_preloaded_records_to_collection(id_to_record_map[through_record[through_primary_key].to_s],
reflection.name, through_record.send(source))
end
end
else
set_association_collection_records(id_to_record_map, reflection.name, find_associated_records(ids, reflection, preload_options),
reflection.primary_key_name)
end
end
def preload_through_records(records, reflection, through_association)
through_reflection = reflections[through_association]
through_primary_key = through_reflection.primary_key_name
if reflection.options[:source_type]
interface = reflection.source_reflection.options[:foreign_type]
preload_options = {:conditions => ["#{connection.quote_column_name interface} = ?", reflection.options[:source_type]]}
records.compact!
records.first.class.preload_associations(records, through_association, preload_options)
# Dont cache the association - we would only be caching a subset
through_records = []
records.each do |record|
proxy = record.send(through_association)
if proxy.respond_to?(:target)
through_records << proxy.target
proxy.reset
else # this is a has_one :through reflection
through_records << proxy if proxy
end
end
through_records.flatten!
else
records.first.class.preload_associations(records, through_association)
through_records = records.map {|record| record.send(through_association)}.flatten
end
through_records.compact!
through_records
end
def preload_belongs_to_association(records, reflection, preload_options={})
options = reflection.options
primary_key_name = reflection.primary_key_name
if options[:polymorphic]
polymorph_type = options[:foreign_type]
klasses_and_ids = {}
# Construct a mapping from klass to a list of ids to load and a mapping of those ids back to their parent_records
records.each do |record|
if klass = record.send(polymorph_type)
klass_id = record.send(primary_key_name)
if klass_id
id_map = klasses_and_ids[klass] ||= {}
id_list_for_klass_id = (id_map[klass_id.to_s] ||= [])
id_list_for_klass_id << record
end
end
end
klasses_and_ids = klasses_and_ids.to_a
else
id_map = {}
records.each do |record|
key = record.send(primary_key_name)
if key
mapped_records = (id_map[key.to_s] ||= [])
mapped_records << record
end
end
klasses_and_ids = [[reflection.klass.name, id_map]]
end
klasses_and_ids.each do |klass_and_id|
klass_name, id_map = *klass_and_id
klass = klass_name.constantize
table_name = klass.quoted_table_name
primary_key = klass.primary_key
conditions = "#{table_name}.#{connection.quote_column_name(primary_key)} IN (?)"
conditions << append_conditions(options, preload_options)
column_type = klass.columns.detect{|c| c.name == primary_key}.type
ids = id_map.keys.uniq.map do |id|
if column_type == :integer
id.to_i
elsif column_type == :float
id.to_f
else
id
end
end
associated_records = klass.find(:all, :conditions => [conditions, ids],
:include => options[:include],
:select => options[:select],
:joins => options[:joins],
:order => options[:order])
set_association_single_records(id_map, reflection.name, associated_records, primary_key)
end
end
def find_associated_records(ids, reflection, preload_options)
options = reflection.options
table_name = reflection.klass.quoted_table_name
if interface = reflection.options[:as]
conditions = "#{reflection.klass.quoted_table_name}.#{connection.quote_column_name "#{interface}_id"} IN (?) and #{reflection.klass.quoted_table_name}.#{connection.quote_column_name "#{interface}_type"} = '#{self.base_class.sti_name}'"
else
foreign_key = reflection.primary_key_name
conditions = "#{reflection.klass.quoted_table_name}.#{foreign_key} IN (?)"
end
conditions << append_conditions(options, preload_options)
reflection.klass.find(:all,
:select => (preload_options[:select] || options[:select] || "#{table_name}.*"),
:include => preload_options[:include] || options[:include],
:conditions => [conditions, ids],
:joins => options[:joins],
:group => preload_options[:group] || options[:group],
:order => preload_options[:order] || options[:order])
end
def interpolate_sql_for_preload(sql)
instance_eval("%@#{sql.gsub('@', '\@')}@")
end
def append_conditions(options, preload_options)
sql = ""
sql << " AND (#{interpolate_sql_for_preload(sanitize_sql(options[:conditions]))})" if options[:conditions]
sql << " AND (#{sanitize_sql preload_options[:conditions]})" if preload_options[:conditions]
sql
end
end
end
end
