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Diffstat (limited to 'activerecord/lib/active_record/association_preload.rb')
| -rw-r--r-- | activerecord/lib/active_record/association_preload.rb | 433 |
1 files changed, 0 insertions, 433 deletions
diff --git a/activerecord/lib/active_record/association_preload.rb b/activerecord/lib/active_record/association_preload.rb deleted file mode 100644 index a34a73cf5d..0000000000 --- a/activerecord/lib/active_record/association_preload.rb +++ /dev/null @@ -1,433 +0,0 @@ -require 'active_support/core_ext/array/wrap' -require 'active_support/core_ext/enumerable' - -module ActiveRecord - # See ActiveRecord::AssociationPreload::ClassMethods for documentation. - module AssociationPreload #:nodoc: - extend ActiveSupport::Concern - - # Implements the details of eager loading of Active Record associations. - # Application developers should not use this module directly. - # - # <tt>ActiveRecord::Base</tt> is extended with this module. The source code in - # <tt>ActiveRecord::Base</tt> references methods defined in this module. - # - # Note that 'eager loading' and 'preloading' are actually the same thing. - # However, there are two different eager loading strategies. - # - # The first one is by using table joins. This was only strategy available - # prior to Rails 2.1. Suppose that you have an Author model with columns - # 'name' and 'age', and a Book model with columns 'name' and 'sales'. Using - # this strategy, Active Record would try to retrieve all data for an author - # and all of its books via a single query: - # - # SELECT * FROM authors - # LEFT OUTER JOIN books ON authors.id = books.id - # WHERE authors.name = 'Ken Akamatsu' - # - # However, this could result in many rows that contain redundant data. After - # having received the first row, we already have enough data to instantiate - # the Author object. In all subsequent rows, only the data for the joined - # 'books' table is useful; the joined 'authors' data is just redundant, and - # processing this redundant data takes memory and CPU time. The problem - # quickly becomes worse and worse as the level of eager loading increases - # (i.e. if Active Record is to eager load the associations' associations as - # well). - # - # The second strategy is to use multiple database queries, one for each - # level of association. Since Rails 2.1, this is the default strategy. In - # situations where a table join is necessary (e.g. when the +:conditions+ - # option references an association's column), it will fallback to the table - # join strategy. - # - # See also ActiveRecord::Associations::ClassMethods, which explains eager - # loading in a more high-level (application developer-friendly) manner. - module ClassMethods - protected - - # Eager loads the named associations for the given Active Record record(s). - # - # In this description, 'association name' shall refer to the name passed - # to an association creation method. For example, a model that specifies - # <tt>belongs_to :author</tt>, <tt>has_many :buyers</tt> has association - # names +:author+ and +:buyers+. - # - # == Parameters - # +records+ is an array of ActiveRecord::Base. This array needs not be flat, - # i.e. +records+ itself may also contain arrays of records. In any case, - # +preload_associations+ will preload the all associations records by - # flattening +records+. - # - # +associations+ specifies one or more associations that you want to - # preload. It may be: - # - a Symbol or a String which specifies a single association name. For - # example, specifying +:books+ allows this method to preload all books - # for an Author. - # - an Array which specifies multiple association names. This array - # is processed recursively. For example, specifying <tt>[:avatar, :books]</tt> - # allows this method to preload an author's avatar as well as all of his - # books. - # - a Hash which specifies multiple association names, as well as - # association names for the to-be-preloaded association objects. For - # example, specifying <tt>{ :author => :avatar }</tt> will preload a - # book's author, as well as that author's avatar. - # - # +:associations+ has the same format as the +:include+ option for - # <tt>ActiveRecord::Base.find</tt>. So +associations+ could look like this: - # - # :books - # [ :books, :author ] - # { :author => :avatar } - # [ :books, { :author => :avatar } ] - # - # +preload_options+ contains options that will be passed to ActiveRecord::Base#find - # (which is called under the hood for preloading records). But it is passed - # only one level deep in the +associations+ argument, i.e. it's not passed - # to the child associations when +associations+ is a Hash. - def preload_associations(records, associations, preload_options={}) - records = Array.wrap(records).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.sum { |record| Array.wrap(record.send(reflection.name)) } - unless parents.empty? - parents.first.class.preload_associations(parents, child) - end - end - end - end - - private - - # Preloads a specific named association for the given records. This is - # called by +preload_associations+ as its base case. - 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 - - # 'reflection.macro' can return 'belongs_to', 'has_many', etc. Thus, - # the following could call 'preload_belongs_to_association', - # 'preload_has_many_association', etc. - 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 = parent_record.association(reflection_name) - association.loaded! - association.target.concat(Array.wrap(associated_record)) - association.set_inverse_instance(associated_record) - end - end - - def add_preloaded_record_to_collection(parent_records, reflection_name, associated_record) - parent_records.each do |parent_record| - parent_record.association(reflection_name).target = associated_record - end - end - - def set_association_collection_records(id_to_parent_map, reflection_name, associated_records, key) - associated_records.each do |associated_record| - parent_records = id_to_parent_map[associated_record[key].to_s] - add_preloaded_records_to_collection(parent_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| - seen_key = associated_record[key].to_s - - #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.key? seen_key - - seen_keys[seen_key] = true - mapped_records = id_to_record_map[seen_key] - mapped_records.each do |mapped_record| - association_proxy = mapped_record.association(reflection_name) - association_proxy.target = associated_record - association_proxy.send(:set_inverse_instance, associated_record) - end - end - - id_to_record_map.each do |id, records| - next if seen_keys.include?(id) - add_preloaded_record_to_collection(records, reflection_name, nil) - end - end - - # Given a collection of Active Record objects, constructs a Hash which maps - # the objects' IDs to the relevant objects. Returns a 2-tuple - # <tt>(id_to_record_map, ids)</tt> where +id_to_record_map+ is the Hash, - # and +ids+ is an Array of record IDs. - def construct_id_map(records, primary_key=nil) - records.group_by do |record| - primary_key ||= record.class.primary_key - record[primary_key].to_s - end - end - - def preload_has_and_belongs_to_many_association(records, reflection, preload_options={}) - - left = reflection.klass.arel_table - - id_to_record_map = construct_id_map(records) - - records.each { |record| record.association(reflection.name).loaded! } - options = reflection.options - - right = Arel::Table.new(options[:join_table]).alias('t0') - - join_condition = left[reflection.klass.primary_key].eq( - right[reflection.association_foreign_key]) - - join = left.create_join(right, left.create_on(join_condition)) - select = [ - # FIXME: options[:select] is always nil in the tests. Do we really - # need it? - options[:select] || left[Arel.star], - right[reflection.foreign_key].as( - Arel.sql('the_parent_record_id')) - ] - - associated_records_proxy = reflection.klass.unscoped. - includes(options[:include]). - order(options[:order]) - - associated_records_proxy.joins_values = [join] - associated_records_proxy.select_values = select - - custom_conditions = append_conditions(reflection, preload_options) - - klass = associated_records_proxy.klass - - associated_records(id_to_record_map.keys) { |some_ids| - method = in_or_equal(some_ids) - conditions = right.create_and( - [right[reflection.foreign_key].send(*method)] + - custom_conditions) - - relation = associated_records_proxy.where(conditions) - klass.connection.select_all(relation.arel.to_sql, 'SQL', relation.bind_values) - }.map! { |row| - parent_records = id_to_record_map[row['the_parent_record_id'].to_s] - associated_record = klass.instantiate row - add_preloaded_records_to_collection( - parent_records, reflection.name, associated_record) - associated_record - } - end - - def preload_has_one_association(records, reflection, preload_options={}) - return if records.first.association(reflection.name).loaded? - id_to_record_map = construct_id_map(records, reflection.options[:primary_key]) - options = reflection.options - - add_preloaded_record_to_collection(records, reflection.name, nil) - - if options[:through] - through_records = preload_through_records(records, reflection, options[:through]) - - unless through_records.empty? - through_reflection = reflections[options[:through]] - through_primary_key = through_reflection.foreign_key - source = reflection.source_reflection.name - through_records.first.class.preload_associations(through_records, source) - if through_reflection.macro == :belongs_to - id_to_record_map = construct_id_map(records, through_primary_key) - through_primary_key = through_reflection.klass.primary_key - end - - 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(id_to_record_map.keys, reflection, preload_options), reflection.foreign_key) - end - end - - def preload_has_many_association(records, reflection, preload_options={}) - return if records.first.send(reflection.name).loaded? - options = reflection.options - - foreign_key = reflection.through_reflection_foreign_key - id_to_record_map = construct_id_map(records, foreign_key || reflection.options[:primary_key]) - records.each { |record| record.association(reflection.name).loaded! } - - if options[:through] - through_records = preload_through_records(records, reflection, options[:through]) - unless through_records.empty? - source = reflection.source_reflection.name - through_records.first.class.preload_associations(through_records, source, options) - through_records.each do |through_record| - through_record_id = through_record[reflection.through_reflection_primary_key].to_s - add_preloaded_records_to_collection(id_to_record_map[through_record_id], reflection.name, through_record.send(source)) - end - records.each { |record| record.send(reflection.name).target.uniq! } if options[:uniq] - end - - else - set_association_collection_records(id_to_record_map, reflection.name, find_associated_records(id_to_record_map.keys, reflection, preload_options), - reflection.foreign_key) - end - end - - def preload_through_records(records, reflection, through_association) - if reflection.options[:source_type] - interface = reflection.source_reflection.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 - records.map { |record| - proxy = record.association(through_association) - - if proxy.respond_to?(:target) - Array.wrap(proxy.target).tap { proxy.reset } - else # this is a has_one :through reflection - [proxy].compact - end - }.flatten(1) - else - options = {} - options[:include] = reflection.options[:include] || reflection.options[:source] if reflection.options[:conditions] - options[:order] = reflection.options[:order] - options[:conditions] = reflection.options[:conditions] - records.first.class.preload_associations(records, through_association, options) - - records.map { |record| - Array.wrap(record.send(through_association)) - }.flatten(1) - end - end - - def preload_belongs_to_association(records, reflection, preload_options={}) - return if records.first.association(reflection.name).loaded? - options = reflection.options - - klasses_and_ids = {} - - if options[:polymorphic] - # 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(reflection.foreign_type) - klass_id = record.send(reflection.foreign_key) - if klass_id - id_map = klasses_and_ids[klass.constantize] ||= {} - (id_map[klass_id.to_s] ||= []) << record - end - end - end - else - id_map = records.group_by do |record| - key = record.send(reflection.foreign_key) - key && key.to_s - end - klasses_and_ids[reflection.klass] = id_map unless id_map.empty? - end - - klasses_and_ids.each do |klass, _id_map| - primary_key = (reflection.options[:primary_key] || klass.primary_key).to_s - keys = _id_map.keys.compact - - unless keys.empty? - table = klass.arel_table - method = in_or_equal(keys) - conditions = table[primary_key].send(*method) - - custom_conditions = append_conditions(reflection, preload_options) - conditions = custom_conditions.inject(conditions) do |ast, cond| - ast.and cond - end - - associated_records = klass.unscoped.where(conditions).apply_finder_options(options.slice(:include, :select, :joins, :order)).to_a - else - associated_records = [] - end - - 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 = reflection.klass.arel_table - - conditions = [] - - key = reflection.foreign_key - - if interface = reflection.options[:as] - key = "#{interface}_id" - conditions << table["#{interface}_type"].eq(base_class.sti_name) - end - - conditions.concat append_conditions(reflection, preload_options) - - find_options = { - :select => preload_options[:select] || options[:select] || table[Arel.star], - :include => preload_options[:include] || options[:include], - :joins => options[:joins], - :group => preload_options[:group] || options[:group], - :order => preload_options[:order] || options[:order] - } - - associated_records(ids) do |some_ids| - method = in_or_equal(some_ids) - where = table.create_and(conditions + [table[key].send(*method)]) - - reflection.klass.scoped.apply_finder_options(find_options.merge(:conditions => where)).to_a - end - end - - def process_conditions(conditions, klass = self) - if conditions.respond_to?(:to_proc) - conditions = instance_eval(&conditions) - end - - klass.send(:sanitize_sql, conditions) - end - - def append_conditions(reflection, preload_options) - [ - ('(' + process_conditions(reflection.options[:conditions], reflection.klass) + ')' if reflection.options[:conditions]), - ('(' + process_conditions(preload_options[:conditions]) + ')' if preload_options[:conditions]), - ].compact.map { |x| Arel.sql x } - end - - def in_or_equal(ids) - ids.length == 1 ? ['eq', ids.first] : ['in', ids] - end - - # Some databases impose a limit on the number of ids in a list (in Oracle its 1000) - # Make several smaller queries if necessary or make one query if the adapter supports it - def associated_records(ids) - in_clause_length = connection.in_clause_length || ids.size - records = [] - ids.each_slice(in_clause_length) do |some_ids| - records.concat yield(some_ids) - end - records - end - end - end -end |